GCSE Acid Reactions by anandjsingh

Acid Reactions

Reactions of Acids Workbook GCSE

Mr Singh

Acid Reactions

4.4.2 Reactions of acids 4.4.2.1 Reactions of acids with metals Content

Key opportunities for skills development

Acids react with some metals to produce salts and hydrogen. (HT only) Students should be able to: • explain in terms of gain or loss of electrons, that these are redox reactions • identify which species are oxidised and which are reduced in given chemical equations. Knowledge of reactions limited to those of magnesium, zinc and iron with hydrochloric and sulfuric acids.

4.4.2.2 Neutralisation of acids and salt production Content

Key opportunities for skills development

Acids are neutralised by alkalis (eg soluble metal hydroxides) and bases (eg insoluble metal hydroxides and metal oxides) to produce salts and water, and by metal carbonates to produce salts, water and carbon dioxide. The particular salt produced in any reaction between an acid and a base or alkali depends on: • the acid used (hydrochloric acid produces chlorides, nitric acid produces nitrates, sulfuric acid produces sulfates) • the positive ions in the base, alkali or carbonate. Students should be able to: • predict products from given reactants • use the formulae of common ions to deduce the formulae of salts.

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GCSE Chemistry 8462. GCSE exams June 2018 onwards. Version 1.0 21 April 2016 Acid Reactions

4.4.2.3 Soluble salts Content

Key opportunities for skills development

Soluble salts can be made from acids by reacting them with solid insoluble substances, such as metals, metal oxides, hydroxides or carbonates. The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt. Salt solutions can be crystallised to produce solid salts. Students should be able to describe how to make pure, dry samples of named soluble salts from information provided. Required practical 1: preparation of a pure, dry sample of a soluble salt from an insoluble oxide or carbonate using a Bunsen burner to heat dilute acid and a water bath or electric heater to evaporate the solution. AT skills covered by this practical activity: 2, 3, 4 and 6. This practical activity also provides opportunities to develop WS and MS. Details of all skills are given in Key opportunities for skills development (page 103).

4.4.2.4 The pH scale and neutralisation Content

Key opportunities for skills development

Acids produce hydrogen ions (H+) in aqueous solutions.

AT 3

Aqueous solutions of alkalis contain hydroxide ions (OH–).

This is an opportunity to investigate pH changes when a strong acid neutralises a strong alkali.

The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution, and can be measured using universal indicator or a pH probe. A solution with pH 7 is neutral. Aqueous solutions of acids have pH values of less than 7 and aqueous solutions of alkalis have pH values greater than 7. In neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water. This reaction can be represented by the equation:

Students should be able to: • describe the use of universal indicator or a wide range indicator to measure the approximate pH of a solution • use the pH scale to identify acidic or alkaline solutions.

Mr Singh

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Acid Reactions

4.4.2.5 Titrations (chemistry only) Content

Key opportunities for skills development

The volumes of acid and alkali solutions that react with each other can be measured by titration using a suitable indicator. Students should be able to: • describe how to carry out titrations using strong acids and strong alkalis only (sulfuric, hydrochloric and nitric acids only) to find the reacting volumes accurately • (HT Only) calculate the chemical quantities in titrations involving concentrations in mol/dm3 and in g/dm3. Required practical 2: (chemistry only) determination of the reacting volumes of solutions of a strong acid and a strong alkali by titration. (HT only) determination of the concentration of one of the solutions in mol/dm3 and g/dm3 from the reacting volumes and the known concentration of the other solution. AT skills covered by this practical activity: 1 and 8. This practical activity also provides opportunities to develop WS and MS. Details of all skills are given in Key opportunities and skills development (page 104).

4.4.2.6 Strong and weak acids (HT only) Content

Key opportunities for skills development

A strong acid is completely ionised in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids.

AT 8

A weak acid is only partially ionised in aqueous solution. Examples of weak acids are ethanoic, citric and carbonic acids.

An opportunity to measure the pH of different acids at different concentrations.

For a given concentration of aqueous solutions, the stronger an acid, the lower the pH. As the pH decreases by one unit, the hydrogen ion concentration of the solution increases by a factor of 10. Students should be able to: • use and explain the terms dilute and concentrated (in terms of amount of substance), and weak and strong (in terms of the degree of ionisation) in relation to acids • describe neutrality and relative acidity in terms of the effect on hydrogen ion concentration and the numerical value of pH (whole numbers only).

MS 2h Make order of magnitude calculations.

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Acid Reactions

Helping yourself Read the section on Chemical Reactions in your textbook Read relevant sections of these websites bbc.co.uk/schools/gcsebitesize/chemistry gcsescience.com docbrown.info revisioncentre.co.uk youtube for video tutorials other teachers and boosters!

Mr Singh

Acid Reactions

Acids An important group of chemicals is called Acids. Acids have a ………………………… taste. Acid comes from the latin for sour ‘acidus’. Sour tasting Vinegar contains ethanoic acid, off milk contains lactic acid, lemons contain citric acid and rancid butter contains butanoic acid. These are all organic acids.

There are also mineral acids which are synthetically made from minerals and more commonly used in the lab like hydrochloric acid, sulfuric acid and nitric acid. Acids occur naturally in the stomach where they aid with digestion by providing the right conditions for the enzyme pepsin to begin the digestion of proteins. It is produced by the stomach’s lining to kill bacteria and soften foods. Acid Ascorbic Acid Carbonic Acid

Strong of Weak Weak Weak

Citric acid Ethanoic acid Hydrochloric acid

Weak Weak Strong

Lactic acid Nitric acid Phosphoric acid Sulfuric acid

Weak Strong Strong Strong

Where it’s found In fruits. Also called vitamin C In fizzy drinks. These contain carbon dioxide dissolved in water In fruit juices, e.g. lemon juice In vinegar In digestive juices in the stomach. Also used for cleaning metals In sour milk Used for making fertilisers and explosives In anti-rust paint and making fertilisers In car batteries and making fertiliser

Acids can also be weak and strong. Mineral acids tend to react more quickly than organic acids as they are stronger acids. Solutions of acids can be dilute or concentrated solutions. A dilute solution contains a small number of acid particles per litre of

Mr Singh

Acid Reactions

solution. A concentrated solution contains a large number of acid practices for litre of solution.

Concentrated acids are very ……………………………. Acids change the colour of substances called ……………………….

Acids react with metals to produce ……………………………… and a salt of the metal

!"#$ + !"#$"%&' !"#$ → !"#$%&'( + !"#$ !"#$%&' !" ! + !! !!! !"

Mr Singh

→

!! !

+ !"#!! (!")

Acid Reactions

Acids react with carbonates to give ………………………………….., salt and water

Magnesium Carbonate is used as a anti-acid tablet for indigestion or the build up of stomach acid.

!"#$%&'() !"#$%&"'( + !"#$%&ℎ!"#$% !"#$ → !"#$%& !"#$"!% + !"#$%&'() !ℎ!"#$%& + !"#$% !"#!! ! + 2!"# !" → !!! ! + !"#!! !" + !! !(!)

!"#$%& ℎ!"#$%&'()#*$')+& + !"!"#$ℎ!"#$% !"# → !"#$%& !"#$"!% + !"#$%& !ℎ!"#$%& + !"#$% !"#$!! ! + !"# !" → !!! ! + !"#$ !" + !! !(!)

Acids neutralise alkalis to form salts and ……………………………. !"#$%& !"#$%&'#( + !"#$%&ℎ!!"#$ !"#$ → !"#$%& !ℎ!"#$%& + !"#$% !"#$ !" + !"# !" → !"#$ !" + !! !(!)

Acids react with metal oxides (bases) to form a ………………………….. and water !"#$ !"#$% + !"#$"% !"#$ → !"#$ !ℎ!"#$%& + !"#$% !"# ! + 2!"# !" → !"#!! !" + !! !(!)

Mr Singh

Acid Reactions

Although an acid does all these things an Acid defined as:

An hydrogen ion H+ ..................

A Swedish chemist called Arrhenius put forward the idea that all acids in solution contain ……………………………. ions, ! ! (!"), in high concentration.

This explains the reactions between acids and other compounds. Ionic equations e.g. metal and acids !"#$% !"#$ + !"#$%&'( !"#$ → !"#$%& !"#$ + ⋯ … … … … … … … … !"#$%&#$' ! !

+ 2! ! !"

→ ! !! !"

+ !! (!)

Or bases and acids !"#$%&'( !"#$ + !"#$ ! ! !"

→ … … … … … … … … … ..

+ !! ! !" → !! !(!)

Or Acids and carbonates !"#$%&"'( + !"#$%&'( !"#$ → !"#$% + ⋯ … … … … … … … … … !!!!! !"

+ 2! ! !"

→ !! ! ! + !!! (!)

A solution which is a strong acid has a much higher .................................. of hydrogen ion than a weak acid and so will react much more vigorously.

Mr Singh

Acid Reactions

Bases & Alkalis Some common domestic and laboratory Alkalis are shown below. They are mainly kitchen cleansers because bases attach grease.

Properties Alkalis feel soapy. Alkali is from the Arabic Al-qaliy meaning calinated ash from which soap was first made. They turn indicators blue or purple Their pH is greater than 7 They react with acids to form a ........................ and water. This is called a .................................... reaction. e.g. Hydrochloric acid and Sodium Hydroxide !"#$%& !"#$%!"#$ + !"#$%&ℎ!"#$% !"#$ → !"#$%& !ℎ!"#$%& + !"#$% !"#$ !" + !"# !" → !"#$ !" + !! !(!) All alkalis except ammonia react with ammonium compounds to form ammonia gas. e.g. !"#$%&' ℎ!"#$%&"' + !""!"#$% !ℎ!"#$%& → !"#!$%& !ℎ!"#$%& + !"#$% + !""#$%! !" !"

2!!! !" !

→

!"!!! !

+ 2!! ! ! + 2!!! (!)

This reaction is used for making ammonia in the laboratory.

Hydroxide ion All Acids contain Hydrogen ions, ! ! . and behave like acids only in solution.

Mr Singh

Acid Reactions

Similarly all alkalis contain .............................. ions, !!! Sodium Hydroxide !"!" Ammonium Hydroxide !!! !" Potassium Hydroxide !!" Calcium Hydroxide !" !"

Dissociation The ions are produced by dissolving the alkalis in water so that they .......................... e.g. Solid sodium hydroxide pellets dissociate in water to form hydroxide ions !"#$%& ℎ!"#$%&"' ! → !"#$%& !"# !" + !"#$%&'#( !"#(!") !"#$ ! → !! ! !" + !! ! (!")

e.g. Ammonia gas dissolves in water to form ammonium ions and hydroxide ions !!! ! + !! ! ! → !!!! !" + !! ! (!") Weak and Strong Also like acids alkalis can dissociate to different extents and therefore can be weak or strong. Strong alkalis dissociate almost completely to form ions in solution Sodium Hydroxide is a strong alkali

Weak alkalis dissociate only partially to form some ions in solution. Ammonia solution is a weak alkali Strong Alkalis Sodium Hydroxide Potassium Hydroxide Calcium Hydroxide

Mr Singh

Weak Alkalis Ammonia

Acid Reactions

The higher the concentration of !! ! ions the stronger the alkali. The stronger the alkali the higher the pH.

Neutralization In the reaction between a solution of sodium hydroxide and a solution of hydrochloric acid a salt and water are formed

!"#$%& ℎ!"#$%&"' + !"#$%&ℎ!"#$% !"#$ → !"#$%& !ℎ!"#$%& + !"#$% !"#$ !" + !"# !" → !"#$ !" + !! !(!) More generally for all ............................................. reactions !"#$ + !"#$ → !"#$ + !"#$%

When both are in solution they are totally ................................... so we can write an equation showing all the ions present. !! ! !" + !! ! !" + ! ! !" + !! ! !" → !! ! !" + !! ! !" + !! !(!) But notice that there are ions in solution which don’t seem to do anything in the reaction as they just remain in solutions unchanged. These are what are called Spectator ions as they just sit and watch. We can therefore reduce a neutralization reaction to the very basic Ionic equation: ! ! !" + !! ! !" → !! !(!)

Mr Singh

Acid Reactions

This Ionic equation is true of all neutralization reactions. All other ions are simply spectating. In a neutralization reaction the !! ions are turned into water molecules. Solid sodium chloride can be obtained by evaporating off all the water molecules. We can track the neutralization reaction by either measuring the pH, the temperature or the conductivity. Some everyday examples of neutralization reactions include putting calamine lotion of bee stings or bicarbonate of soda on wasp stings, drinking milk of magnesia to tackle indigestion, reducing acidity of soil by adding slaked lime or treating factory waste.

Bases Alkalis are........................ bases. Most bases are metal hydroxides and oxides and are insoluble in water. e.g. !"#$%&' !"#$%&'#( ! + !"#$"% !"#$ !" → !"#$%&' !"#$%#& !" + !"#$% ! !" !"

! + 2!"!! !" → !" !!!

!" + !! !(!)

We therefore define a Base as: A chemical substance which reacts with an acid to form salt and water only. In the process of neutralization a base accepts the donated ! ! ion or proton from the acid.

!"#$ !" + !"# !" → !"#$ !" + !! !(!) Base

Mr Singh

Acid

Salt

Water

Acid Reactions

Sodium Hydroxide ............................. the !! from the acid which donates it.

! ! !" + !! ! !" â&#x2020;&#x2019; !! !(!) We therefore define a base as

A !!acceptor or a proton .......................

This is the exact opposite of our definition for an acid. Some examples of bases Metal Oxides Copper (II) Oxide, CuO Zinc Oxide, ZnO

Metal Hydroxides Sodium Hydroxide, NaOH Magnesium Hydroxide, Mg(OH)2

Alkalis Sodium Hydroxide, NaOH Potassium Hydroxide, KOH Calcium Hydroxide, Ca(OH)2 Ammonia solution, NH3(aq)

Uses of bases Base Ammonia

Strong or weak Weak

Calcium Hydroxide Calcium Oxide

Strong Strong

Magnesium Hydroxide

Strong

Sodium Hydroxide

Strong

Mr Singh

Where you find it Cleaning fluids and making fertilisers Treating acidic soil Manufacture of cement, mortar and concrete Anti-acid indigestions tablets and milk of magnesia Oven cleaners and soap manufacturer

Acid Reactions

Making Soluble Salts Salts are essential to life. They are the result of a reaction of an acid. They have ionic structures and are represented by dot cross diagrams.

Salts are produced when the hydrogen ions have been replaced by metal ions or by an ammonium ion. They all have names which describe their parent ……………………. All salts made from hydrochloric acid are called …………………….. All salts of Sulfuric acid are called ……………………. Salts on nitric acid are called ………………………….. Acids Hydrochloric acid, HCl(aq)

Sulfuric acid, H2SO4

Nitric acid, HNO3

Salts Sodium chloride, NaCl Calcium chloride, CaCl2 Iron(II) chloride, FeCl2 Ammonium chloride, NH4Cl Sodium sulphate, Na2SO4 Zinc sulphate, ZnSO4 Iron(III) sulphate, Fe2(SO4)2 Sodium nitrate, NaNO3 Copper(II) nitrate, Cu(NO3)2

Useful salts Salt Ammonium nitrate Ammonium sulfate Sodium carbonate -10-waters Calcium sulphate Iron(II) sulphate-7-water Barium sulfate Calcium fluoride Silver Bromide

Mr Singh

Common usage Fertiliser Fertiliser Water softener Plaster of paris Treating anaemia X-rays of digestive tracts Protecting teeth enamel Black and White photography

Acid Reactions

Making Salts The method you choose to make a salt depends on whether it is soluble or insoluble. ……………………. salts are made by neutralizing an acid. ……………………………….. salts are made by adding two solutions Here is a table containing the solubility of various important salts. Salts Chlorides

Soluble Most are soluble

Sulfates

Most are soluble

Nitrates Carbonates

All are soluble Sodium carbonate Potassium carbonate All are soluble All are soluble All are soluble All are soluble

Ethanoates Sodium salts Potassium salts Ammonium salts

Insoluble Silver chloride Lead(II) chloride Barium Sulfate Calcium sulphate Lead(II) sulphate None Most are insoluble None None None None

It is best to learn whether most are soluble or insoluble and then the exceptions. Methods of making soluble salts An acid is neutralized by a base such as a metal, a metal oxide, a metal carbonate or solution of an alkali Method 1: Acid + Metalà Salt }+ Hydrogen Method 2: Acid + Metal oxide à Salt + Water Method 3: Acid + Metal Carbonate à Salt + Water + Carbon Dioxide Method 4: Acid + Alkali à Salt + Water

a) Using an Insoluble Base For methods 1-3 Step 1and 2: Warm the acid and add Base until there is excess vase and no more reaction occurs

Mr Singh

Acid Reactions

Step 3:Remove excess base through filtrating Step: 4 Leave to crystallize e.g. !"##$% !"#$% + !"#$"%&' !"#$ â&#x2020;&#x2019; !"##$% !"#$%&' + !"#$% !"# !

+ !! !!! !"

â&#x2020;&#x2019; !"#!! !"

+ !! !(!)

b) Using a soluble base (alkali) For Method 4 Step 1: Pipette acid into conical flask and add indicator Step 2: Fill burette with alkali and set it at the zero mark Step3: Titrate in just enough that the indicator just turns. Step 4: Repeat experiment without indicator using exactly the same quantities. Evaporate to saturation over a Bunsen. Step 5: Leave to crystallise.

Making Insoluble salt Insoluble salts are made by mixing two solutions. This method is called precipitation.

e.g.

Mr Singh

Acid Reactions

!"#$%& !ℎ!"#$%& + !"#$%& !"#$%& → !"#$%& !"#$%&' + !"#$%& !ℎ!"#$%& !"#!! !"

+ !!! !!! !"

→ !"#!! !

+ !"#$ !"

The ionic equations for the reaction is !"#$%& !"#$ + !"#$%&' !"#$ → !"#$%& !"#$%&' !! !! !"

Mr Singh

+ !!!!! !"

→ !"#!! (!)

Acid Reactions

Indicators and pH Scale An indicator turns a different ................... when put in different acidic or alkali environments Indicator Litmus Phenolphthalein Methyl Orange

Acidic Colour .............. Colourless Red

Neutral colour Purple Colourless .....................

Alkaline Colour Blue ................. Yellow

Universal Indicator turns a different colour in strongly or weakly acidic solutions and strongly and weakly alkali solutions.

The pH scale is a .......................... measure of the concentration of.................................ions in solutions. Each colour for universal indicator has its own number. pH 0 is the most acidic a substance can be when there is complete dissociation into ions. pH14 is the most alkali a substance can be where there is complete dissociation into ions.

Mr Singh

Acid Reactions

SOLUBILITY RULES WHAT IS SOLUBILITY? The proper definition of the solubility of a solid in water is the maximum mass of solid which can be dissolved in 100g (100 cm3) of water. Solubility varies with the temperature of the water. For many solids, solubility increases as the temperature increases. A guideline to deciding whether to classify a solid as soluble or insoluble in water at room temperature is given below:Soluble Sparingly soluble Insoluble -

more than 1 gram of solid will dissolve in 100g of water between 0.1g and 1g dissolve in 100g water less than 0.1g will dissolve in 100g water

The tables below show the rules you need to know for GCSE. You must learn them off by heart! BASES – assume bases are INSOLUBLE and learn the exceptions These are metal oxides, metal hydroxides, metal carbonates and ammonia (NH3). Soluble bases are called ALKALIS. These are generally from Group I of the Periodic Table (sodium, potassium, etc.). [Memory Aid: Group I is called “The Alkali Metals”]. Ammonia is a highly soluble gas which produces an alkaline solution called “aqueous ammonia” or “ammonium hydroxide”. ♦ ALL metal carbonates are INSOLUBLE except sodium and potassium. ♦ ALL metal hydroxides are INSOLUBLE except Group I. Calcium hydroxide is slightly soluble (the solution is called limewater) ♦ ALL metal oxides are INSOLUBLE except Group I. Calcium oxide is slightly soluble.

SALTS – assume salts are SOLUBLE and learn the exceptions The common salts are chlorides, sulphates and nitrates. ♦ ALL sodium and potassium salts are soluble. ♦ ALL ammonium salts are soluble. ♦ ALL nitrates are soluble. ♦ ALL chlorides are soluble except silver and lead (PbCl2 dissolves in hot water) ♦ ALL sulphates are soluble except barium, lead and calcium (although calcium sulphate is very sparingly soluble – rather borderline!)

Mr Singh

Acid Reactions

1203WS

Solubility Rules

Soluble Compounds All Group 1 and ammonium salts All nitrate salts Most chloride salts

Except silver and lead chlorides

Most sulphate salts

Except barium, lead and calcium sulphates

Insoluble Compounds

Mr Singh

Most hydroxides

Except Group 1 and ammonium hydroxides

Most oxides

Except Group 1 and ammonium oxides

Most carbonates

Except Group 1 and ammonium carbonates

Acid Reactions

Volumetric analysis

TITRATIONS Scope

Volumetric analysis is a practical technique whereby one uses reacting volumes to analyse and calculate a variety of unknown values. It can be used to find the ...

• • • • • •

concentration of a solution molecular mass of a substance percentage purity of a substance formula of a substance percentage composition of an element present stoichiometry of an equation

In order to obtain accurate results, one needs to carry out each titration with precision. The following notes describe the various operations and techniques involved in volumetric analysis. A guide to the different types of titration and to the calculations involved is also included.

Apparatus

It is essential that all apparatus used in volumetric analysis is free from any contamination. In most cases it is not necessary to have dry apparatus as long as it has been rinsed thoroughly with the purest form of water available (usually de-ionised or distilled water). In all cases, apparatus will not be accurate unless it is used correctly. Graduated equipment such as burettes, pipettes and graduated flasks must not be rinsed with hot water otherwise they will no longer be accurate. Check the information marked on them.

Burette

The burette is a device for accurate delivery of variable amounts of liquid within its range.

before use

Rinse the inside of the burette with distilled water, including the portion below the tap, and tip the washings away; repeat this procedure. This procedure cleans the burette of any impurities that may have accumulated when not in use. Now pour in a small amount of the solution to be used in the burette. Rotate the burette in an almost horizontal position so that the liquid washes all of the inside then let it all drain out through the tap. The burette can then be filled with the solution to a point above the top gradation. Open the tap and let some solution drain out so that the top of the liquid column is within the scale and the section below the tap is completely filled with solution. Check to see that there aren’t any air bubbles.

operation

Read the burette to two decimal places; the second decimal place can be estimated. The normal method is to read the bottom of the meniscus (see diagram) but if the solution is dark coloured such as potassium manganate(VII), one reads the top of the meniscus. Always read the level against a constant background; you will see different positions for the meniscus if you don’t. Traditionally, one operates the tap with ones left hand and agitates the flask with the right. The tip of the burette is placed just below and inside the rim of the conical flask. Near the end point the solution has to be added by the drop, any solution clinging to the jet can be washed into the flask using distilled water.

after use

2.0

3.0

Discard any remaining solution then rinse out thoroughly with water. Loosening the tap a small amount allows water to rinse away any solution trapped inside. Certain solutions can cause problems if left in the burette ... sodium hydroxide

can cause glass parts to “seize up” so prior to rinsing with water, add a small amount of dilute hydrochloric acid.

potassium manganate(VII)

leaves a brown stain if not completely removed. Add some acidified hydrogen peroxide solution before rinsing with water.

Mr Singh

Volumetric analysis

Acid Reactions

Pipette

A pipette is designed to deliver only one volume accurately; the value is stated on the bulb of the pipette. Always use a special filler for drawing liquid into a pipette NEVER USE YOUR MOUTH.

before use

As with burettes, rinse twice with distilled water by draw a small amount into the pipette and rotating it to wash all the inside. Discard both washings. Draw a small amount of the liquid to be used into the pipette and repeat as with water.

operation

Using the filler, draw sufficient liquid into the pipette until the level is above the mark then carefully allow it to run out until the bottom of meniscus is exactly on the mark. This can be done by using the special tap on the filler or by detaching the filler and controlling the descent with a thumb or fore-finger. If the level falls below the mark, draw more liquid back into the pipette.

25ml

Without letting any liquid drain out, place the tip of the pipette into the mouth of a clean (rinsed out with distilled water) conical flask and allow the solution to drain into the flask (NEVER BLOW OR FORCE THE LIQUID OUT). You will notice that a small amount of liquid is left in the jet. Carefully touch the jet onto the surface of the solution in the flask and the level in the jet will fall further. Some liquid remains in the jet; allowance has been made for this during the calibration of the apparatus. after use

Rinse thoroughly with water after use and place back in the rack.

Graduated Flask

Used to prepare solutions of known concentration. The volume is stated on the flask.

before use

Rinse thoroughly with distilled water and discard washings. Do not rinse with the solution you are going to put in it.

operation

Transfer your solution into the flask using a funnel so that all the solution gets into the flask. Rinse original container to get all the solution out, then rinse the remaining solution from the funnel. In this way all the original solution is transferred to the flask. Remove the funnel and carefully add further distilled water until the bottom of the meniscus is exactly on the line. Place the stopper in the flask and invert it and shake to aid mixing. Repeat this operation many times otherwise it will not be of equal concentration throughout

after use

Drain and rinse thoroughly with water after use.

Weighing

All weighings involving analysis must be done on the most accurate balance possible. Solids are weighed in small glass weighing bottles. One must never place wet or hot objects on a balance or touch the pan with fingers. In most experiments you will be given a range within which you must weigh. • • • • • •

Place a weighing bottle (+ lid) on a two-place balance then tare it. Add sufficient solid so that the value is in the range required. Transfer the container (and lid) + solid to the accurate balance and record the mass * Tip the solid into the required vessel, tapping the bottom of the bottle to dislodge the contents Re-weigh the bottle to find the amount that has been transferred Leave the balances in a tidy state for the next person.

* one can tare the balance instead at this stage; it will save you having to subtract two values! Mr Singh

Volumetric analysis

Acid Reactions

Indicators

Most titrations involve the use of an indicator to detect the end point; the indicator is added to the contents of the titration flask. It is important that you follow the instructions as to when to add the indicator and how much indicator to use. In acid-base titrations, the choice of indicator depends on the pH change occurring at the end-point. e.g.

phenolphthalein methyl orange starch potassium chromate fluorescein

strong base v. weak acid strong acid v. weak base titrations involving iodine (e.g. with sodium thiosulphate) silver nitrate titrations ditto

Variations in analytical method Methods

Two basic techniques can be used. The solution in the burette is added to a) a known volume of solution (measured by pipette) in the flask

b) a known mass of solute weighed into the flask and dissolved in distilled water - this method is known as titrating against weighed aliquots. Both methods involve the same basic techniques but have different methods for checking the concordancy of readings.

Concordance

Theoretically one should get consistent (concordant) results for a set of titrations. In the former method, one checks concordancy by comparing the similarity of titres ... one would expect to deliver the same volume each time. Two titres within 0.1 cm3 of each other is considered acceptable. In the weighed aliquot method, one checks for similarity of titre/mass ratios (volume added / mass used) ... the more you weigh out, the larger the volume of solution one will need to add. Suitable concordancy ranges for titre/mass ratios depend on the titration. N.B.

Concordant results are not necessarily accurate. They could be consistently wrong!

Experiments involving volumetric analysis Acid-base

• • • • •

Standardisation of sodium hydroxide using a standard solution of hydrochloric acid.. Standardisation of hydrochloric acid using a standard solution of sodium carbonate. Estimation of the water of crystallisation in washing soda using weighed aliquots. Determination of the molecular mass of an organic acid using standard sodium hydroxide. Analysis of a carbonate/hydrogencarbonate mixture by the “double indicator” method.

Redox

• • • • • •

Standardisation of a solution of potassium manganate(VII) using potassium ethanedioate. Calculation of the percentage of iron in an iron(II) compound Standardisation of sodium thiosulphate solution using potassium manganate(VII). Calculation of the percentage of copper in a compound using sodium thiosulphate. Determination of the available chlorine in bleach. Estimation of the concentration of alcohol in blood using potassium dichromate(VI).

Complexiometric

• Standardisation of a solution of EDTA. • Use of EDTA to determine the hardness of water.

Mr Singh

Acid Reactions

Strong and Weak acids An acid is defined as a Hydrogen Ion (!! ) ………………... All Acids contain ……………………….. Sulfuric acid !! !!! Nitric acid !!!! Hydrochloric acid !!" Phosphoric acid !! !!! Ethanoic acid !!! !""! The characteristic reactions of acids occur because an acid is ……………………. a Hydrogen ion to another compound. e.g. A neutralisation reaction Sodium Hydroxide + Hydrochloric acid -> Sodium Chloride + Water

!"#$ !" + !"# !" → !"#$ !" + !! !(!) Hydrogen ion is donated by the HCl to the OH- ion to form water.

e.g. An acid and carbonate reaction Hydrochloric acid and calcium carbonate

!"!!! ! + !"# !" → !"!!! !" + !! ! ! + !!! (!) Hydrogen ion is donated by the HCl to the !!!!! carbonate ion to form carbon dioxide and water

Mr Singh

Acid Reactions

Dissociation But Hydrogen ions can only be donated when the acid is in ……………………. This is because the acid needs to DISSOCIATE into its ions and from the ………………………. ion. e.g. Hydrogen Chloride gas when dissolved in water becomes Hydrochloric acid after it has dissociated into its ions. !"#$%&'( !ℎ!"#$%& ! → ℎ!"#$%&' !"#$(!") + !ℎ!"#$%& !"#$(!") !"# ! → ! ! !" + !! ! (!")

The dissociated hydrogen ions give it its acidic nature as they are now free to be donated and react.

The higher the concentation of !! in solutions, the more acidic it is. In other words: •

the more ! ! , the lower the pH,

•

the less ! ! , the higher the pH.

•

The pH scale is a measure of the concentration of ! ! .

•

The lower the pH the more reactive the acid is.

Weak and Strong acids Not all acids dissociate into their ions to the same extent when dissolved in water.

Strong acids dissociate completely. 100% of all HCl molecules break up into ions. !"# ! → ! ! !" + !! ! (!")

Mr Singh

Acid Reactions

Weak acids only partially dissociate. Only one in 1000 or 10,000 ethanoic acid molecules break up into ions. !!! !""# !" â&#x2021;&#x152; !"!#! ! !" + ! ! (!") Strong acids Hydrochloric acid Sulfuric acid Nitric acid

Weak acids Ethanoic acid Citric acid Carbonic acid

A Hydrogen ion contains one proton and no electrons and therefore a hydrogen ion is simply a proton.

So we can define an acid as a Proton Donor.

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Acid Reactions

Acids and Metals 1. Name three common acids [3]

2. Name three metals [3]

3. Give the word equations with state symbols for the following reactions: a. Calcium and hydrochloric acid [2]

b. Magnesium and sulphuric acid [2]

c. Zinc and Nitric acid [2]

4. Give the symbol equations with state symbols for the following reactions: a. Magnesium and Sulphuric acid [3]

b. Aluminium and Hydrochloric acid [3]

5. Name two metals which would not react with an acid [2]

6. Write a general equation for the reaction between acid and metals [2]

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Acid Reactions

Basic Acid reactions 1. Name 3 common strong acids and write their chemical symbol

2. Which ion is involved in every acid reaction?

3. What is the definition of an acid?

4. Calcium carbonate reacts with Hydrochloric acid. a. Write out the word equation

b. Now write out the chemical symbol equation

c. Now divide the chemical into their ions

d. Cancel out the ions present on both sides (spectator ions)

e. Finally write out the ionic equation

Mr Singh

Acid Reactions

4th Form worksheet

Neutralization Reactions Write the word and chemical symbol equations for the reactions between the following chemical substances. 1. Sodium Hydroxide + Hydrochloric acid

2. Lithium hydroxide + Sulfuric acid

3. Calcium Oxide + Nitric acid

4. Potassium Hydroxide + Ethanoic acid

5. Copper Oxide + Sulfuric acid

6. Aluminium oxide + Hydrochloric acid

7. Magnesium Oxide + Nitric acid

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Acid Reactions

5. Copper Oxide reacts with Sulfuric acid a. For this reaction write out the word equation

b. Now write out the chemical symbol equation

c. Now divide the chemical into their ions and cancel out the spectator ions

d. Write out the ionic equation

6. Magnesium reacts with Nitric acid a. For this reaction write out the chemical symbol equation

b. Now divide the chemical into their ions

c. Write out the ionic equation

Mr Singh

Acid Reactions

1201WS GCSE Acids 03 © RWGrime

26/08/16

NAMING SALTS Complete the table below to show the name of the salt formed when the following acids react with the following bases.

hydrochloric acid

sulphuric acid

nitric acid

sodium hydroxide

magnesium oxide

potassium carbonate

sodium hydrogen carbonate

calcium

Now complete the following word equations for reactions between some acids and some bases. 1)

potassium hydroxide + sulphuric acid → …………………………………………………………………………………

nitric acid + sodium oxide → ………………………………………………………………………………………………

iron carbonate + nitric acid → ………………………….…………………………………………………………………

hydrochloric acid + zinc → ………………………………………………………………………………………………..

hydrochloric acid + barium hydroxide → …………………………………………………………………………………

sulphuric acid + potassium carbonate → ……………………………..………………………………………

iron + hydrochloric acid → ………………………….……………..………………………………………………………

nitric acid + lead oxide → …………………………………………………….…………………………………………..

…………………………………………………………………….…… → copper sulphate + water + carbon dioxide

10) …………………………………………………………………………………………….…… → hydrogen + zinc nitrate 11) copper oxide + …………………………………… → copper sulphate + ……………………………………………. 12) hydrochloric acid + ……………………………………. → ………………………………………..… + lead chloride 13) ………………………………………… + sulphuric acid → ….……………………………….. + strontium sulphate

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Acid Reactions

1202WS

Predicting the Salt Formed - Worksheet There are five general methods of making a salt: 1. Acid + Base = Salt 2. Acid + Alkali = Salt 3. Acid + Metal = Salt 4. Acid + Carbonate = Salt 5. Salt + Salt = Salt

+ + + + +

Water Water Hydrogen Carbon dioxide + Salt

Water

Complete the following word equations, and then convert them into balanced symbol equations: 1. Sodium hydroxide

Nitric acid

2. Barium hydroxide

Sulphuric acid

3. Lead oxide

Hydrochloric acid =

4. Iron (III) oxide

Nitric acid

5. Zinc carbonate

Nitric acid

6. Zinc chloride

Lead nitrate

7. Zinc

Sulphuric acid

8. Potassium

Sulphuric acid

9. Sodium carbonate

Sulphuric acid

10. Lithium carbonate

nitric acid

To practice mass calculations, work out what mass of the second reactant is needed to react with the following mass of the first reactant: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

120 g 342 g 1338 g 8g 500g 17g 65 g 78 g 53 g 7.4 g

Mr Singh

Acid Reactions

1203WS

Solubility Worksheet The aim of this exercise is to gain a better understanding of how salts can be made experimentally. You will also practice writing balanced symbol equations and can extend the exercise to include mass calculations. Add state symbols to the following balanced symbol equations (assume there is water present). The solubility Rules on the reverse of this sheet should help you. 1. Zn

H2SO4

Zn SO4

2. 2Na

H2SO4

Na2SO4

3. 2NH3

H2SO4

(NH4)2SO4

4. 2KNO3

CaCl2

Ca(NO3)2

2KCl

5. (NH4)3PO4

3NaOH

3NH3

Na3PO4

6. Al2O3

2HNO3

2Al(NO3)3

H 2O

7. 2KCl

PbF2

2KF

PbCl2

8. CaCO3

2HCl

CaCl2

CO2

9. Fe2O3

6HCl

2FeCl3

3H2O

10. Mg(NO3)2

H2SO4

MgSO4

2HNO3

H2O

Complete the following word equations and then write balanced symbol equations including state symbols: 11. 12. 13. 14. 15.

Sodium chloride Lithium nitrate Calcium chloride Calcium chloride Barium chloride

+ + + + +

lead nitrate à lead chloride à lithium sulphate à lead nitrate à calcium sulphate à

For each of the reactions 11-15, decide which would be a good method of producing a salt by precipitation. Draw diagrams of three beakers showing the particles present before the reaction (in the first 2 beakers) and the particles present once the two reactants have been mixed.

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Acid Reactions

Titration Mole Calculations 1. Give the word equation for the neutralization reaction between hydrochloric acid and sodium hydroxide.

Complete these equations and balance them:

!"# + !"#$

â&#x2020;&#x2019;

!! !!! + !"(!")2

â&#x2020;&#x2019;

3. A _______________ is a laboratory method used to determine the concentration of an acid or a _______________ in solution by performing a _______________ reaction with a standard solution.

4. At the ________________________________ of the titration, the indicator changes colour, which indicates neutralization. Once neutralized, moles of _______________ and moles of _______________ are equal.

5. Calculate the how many moles in the following : a. 25.60 cm3 of 0.2M HCl

b. 30.50 cm3 of 1.5M NaOH

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Acid Reactions

c. 12.55 cm3 of 0.01M KOH

6. What are the molar ratios in the following reactions between acids and akalis? a. !"# !" + !"# !" → !"# !" + !! !")

b. !! !!! !" + 2!"#$ → !!! !!! !" + !! ! !

c. 2!"!! !" + !" !"

!" → !" !!!

!" + 2!! !(!)

7. Calculate the molarity of the following a. 0.2 mol in 200 cm3

b. 0.01 mol in 250 cm3

c. 0.253 mol in 100 cm3

In a titration of HCl with NaOH, 25.30 cm3 of the base was required to neutralize 20.0 cm3 of 0.5 M HCl.

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Acid Reactions

a. Calculate the number of moles of HCl

b. Write out the chemical formula for the reaction

c. Work out the number of moles of NaOH that would have reacted

d. Calculate the molarity of the NaOH?

In a titration of H2SO4 with NaOH, 30.05 cm3 of 0.020 M NaOH was needed to neutralize 15.25 cm3 of H2SO4. a. Calculate the number of moles of NaOH

b. Write out the chemical formula for the reaction

c. Work out the number of moles of H2SO4that would have reacted

Mr Singh

Acid Reactions

d. Calculate the molarity of the H2SO4?

10. If 10.0 cm3 of 0.300 M KOH are required to neutralize 30.0 cm3 of HCl, what is the molarity of the HCl? a. Calculate the number of moles of KOH

b. Write out the chemical formula for the reaction

c. Work out the number of moles of HClthat would have reacted

d. Calculate the molarity of the HCl?

Mr Singh

Acid Reactions

a) Use the volume and concentration of one reactant to calculate the moles.

concentration (mol/dm3)

b) Use the chemical equation to find the moles of the other reactant.

moles volume (dm3)

c) Calculate the volume or concentration as required of that reactant. moles

You could still use the ! and ? that you used for reacting mass calculations in C2. 1)

conc

vol (dm3)

What volume of 0.100 mol/dm sulphuric acid reacts with 30 cm of 0.150 mol/dm sodium hydroxide? 2 NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2 H2O(l) MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM.

25.0 cm of 0.200 mol/dm sodium hydroxide solution reacted with 28.7 cm 3 concentration of the sulphuric acid in mol/dm .

sulphuric acid.

Calculate the

2 NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + 2 H2O(l) MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. 3)

22.5 cm of sodium hydroxide solution reacted with 25.0 cm of 0.100 mol/dm hydrochloric acid. NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l) 3

a) Calculate the concentration of the sodium hydroxide solution in mol/dm . MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. 3

b) Calculate the concentration of the sodium hydroxide solution in g/dm . MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. 4)

What volume of 0.150 mol/dm rubidium hydroxide reacts with 25.0 cm of 0.240 mol/dm nitric acid? RbOH(aq) + HNO3(aq) → RbNO3(aq) + H2O(l) MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM. MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM.

21-July-13

Chemsheets GCSE 117 39

Acid Reactions

What volume of 1.50 mol/dm potassium hydroxide reacts with 25.0 cm of 1.10 mol/dm nitric acid? KOH(aq) + HNO3(aq) → KNO3(aq) + H2O(l) GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG.

25.0 cm of arsenic acid, H3AsO4, required 37.5 cm of 0.100 M sodium hydroxide for neutralisation. Calculate the 3 concentration of the acid in mol/dm . 3 NaOH(aq) + H3AsO4(aq) → Na3AsO4(aq) + 3 H2O(l) GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG.

50.0 cm of 0.250 mol/dm barium hydroxide solution reacted with 24.3 cm of hydrochloric acid. Calculate the 3 concentration of the hydrochloric acid in mol/dm . Ba(OH)2(aq) + 2 HCl(aq) → BaCl2(aq) + 2 H2O(l) GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG.

25.0 cm of 0.150 mol/dm nitric acid reacted with 30.3 cm of a solution of ethanoic acid. CH3COOH(aq) + HNO3(aq) → CH3COONO3 (aq) + H2O(l) 3

a) Calculate the concentration of the ethanoic acid in mol/dm . GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. 3

b) Calculate the concentration of the ethanoic acid in g/dm . GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. 9)

A 0.1575 g sample of ethanedioic acid crystals, H2C2O4.nH2O was dissolved in water. In a titration, 25.0 cm3 of this 3 solution of acid reacted with exactly 15.6 cm3 of 0.16 mol/dm NaOH. Calculate the value of Mr of the acid and n. H2C2O4.nH2O(aq) + 2 NaOH(aq) → Na2C2O4(aq) + (2+n) H2O(l) GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG. GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG.

21-July-13

Chemsheets GCSE 117 40

Acid Reactions

4th Form worksheet

Theory of Acids What is the Bronsted-Lowry definition of an acid? ………………………………………………………………………………………………………………………………………………

What is the Bronsted-Lowry definition of a base? ………………………………………………………………………………………………………………………………………………

When does an acid behave like an acid? ………………………………………………………………………………………………………………………………………………

What ion is responsible for this behaviour? ………………………………………………………………………………………………………………………………………………

What happens when to hydrogen chloride when it is dissolved in water? ………………………………………………………………………………………………………………………………………………

Will hydrogen chloride react with magnesium when dissolves in methylbenzene? ………………………………………………………………………………………………………………………………………………

What is a strong acid? ………………………………………………………………………………………………………………………………………………

What is a weak acid? ………………………………………………………………………………………………………………………………………………

Mr Singh

Acid Reactions

Hydrochloric acid is a strong acid. What is meant by the term acid? .................................................................................................................................. .................................................................................................................................. [Total 1 mark]

A small amount of solid magnesium oxide, MgO, was reacted with excess dilute hydrochloric acid. (i)

Define an acid. ......................................................................................................................... [1]

(ii)

Write a balanced equation for this reaction. ......................................................................................................................... [1] [Total 2 marks]

Ammonium compounds such as ammonium sulfate, (NH4)2SO4, can be used as fertilisers. (i)

Write a balanced equation to show how ammonium sulfate could be formed by the reaction between aqueous ammonia and sulfuric acid. ......................................................................................................................... [1]

(ii)

Ammonium sulfate is an example of a salt formed when an acid is neutralised by a base. Explain what is meant by the term salt. ......................................................................................................................... ......................................................................................................................... [1]

(iii)

Why is ammonia acting as a base in this neutralisation? .........................................................................................................................

Mr Singh

Acid Reactions

......................................................................................................................... [1]

(iv)

What is the relative formula mass of (NH4)2SO4? Give your answer to one decimal place. ......................................................................................................................... [1] [Total 4 marks]

A student carries out experiments using acids, bases and salts. Calcium nitrate, Ca(NO3)2, is an example of a salt. The student prepares a solution of calcium nitrate by reacting dilute nitric acid, HNO3, with the base calcium hydroxide, Ca(OH)2. (i)

Why is calcium nitrate an example of a salt? ......................................................................................................................... ......................................................................................................................... [1]

(ii)

Write the equation for the reaction between dilute nitric acid and calcium hydroxide. Include state symbols. ......................................................................................................................... [2]

(iii)

Explain how the hydroxide ion in aqueous calcium hydroxide acts as a base when it neutralises dilute nitric acid. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... [1] [Total 4 marks]

Mr Singh

Acid Reactions

Taking it further Why not do an internet search for Michael Faraday? What can you find out about him and what was he famous for? Take the some time to look up the subject in an A-level textbook or an old GCSE one. What other industrial uses does electrolysis have? How else does the reactivity series affect our daily lives? How does the reactivity of a metal affect how it has to be extracted from itâ&#x20AC;&#x2122;s ore? How does the reactivity of a metal affect which metal we choose to use for any application? Read some books from the library or order them on amazon: A Short History of Nearly Everything, Bill Bryson Reactions: The Private Life of Atoms, Peter Atkins Why Reactions Happen: James Keeler, Peter Wothers What Einstein Told His Cook: Kitchen Science Explained, Robert L Wolke Read sections of the following websites biography.com famousscientists.org rigb.org Watch these documentaries: The Chemistry of Almost Everything, OU, 31 separate episodes Joe Genius Bill Nye the Science Guy

The Naked Scientist Podcast

Mr Singh

Acid Reactions

Chemical properties of sulphuric acid 1. As an acid (a) Place a small volume of 1M sulphuric acid into a small beaker. Test the solution with litmus and universal indicator paper. ___________________________________________________________________________ _________________________________________________________________________[2] (b) Now add 5 cm3 of 1M sulphuric acid to two test tubes. Add a few drops of phenolphthalein to one and a few drops of methyl orange to the other. ___________________________________________________________________________ _________________________________________________________________________[2] (c) Put a small volume of 0.1M sulphuric acid into a small beaker. Test the solution with litmus and universal indicator solution. _________________________________________________________________________ ________________________________________________________________________[2] (d) Put 10 cm3 of 2M sulphuric acid into a test tube. Add a piece of magnesium ribbon to it. Test the gas produced. ___________________________________________________________________________ _________________________________________________________________________[3] Word equation with state symbols: ________________________________________________________________________[2] Balanced equation: _________________________________________________________________________[1] Ionic equation: _________________________________________________________________________[2] (e) Put 10 cm3 of 2M sulphuric acid into a test tube. Add a piece of calcium into it. ___________________________________________________________________________

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Acid Reactions

_________________________________________________________________________[2] Word equation with state symbols: ________________________________________________________________________[2] Balanced equation: _________________________________________________________________________[1] Ionic equation: _________________________________________________________________________[2] (f) Put 10 cm3 of 2M sulphuric acid into a test tube. Add a piece of aluminium cooking foil into it. Warm if necessary. Test the gas produced. ___________________________________________________________________________ _________________________________________________________________________[3] Word equation with state symbols: ________________________________________________________________________[2] Balanced equation: _________________________________________________________________________[2] (g) Put 10 cm3 of 2M sulphuric acid into a boiling tube and warm up carefully until it reaches about 50oC. Take it away from the heat and add a spatula of copper(II)oxide. Let the reaction subside. Repeat with another spatula of copper(II)oxide. _________________________________________________________________________ ________________________________________________________________________[2] Word equation with state symbols: _______________________________________________________________________[2] Balanced equation: _______________________________________________________________________[1]

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Acid Reactions

(h) Put 10 cm3 of 2M sulphuric acid into a boiling tube and warm up carefully until it reaches about 50oC. Take it away from the heat and add a spatula of nickel(II)carbonate. Let the reaction subside. Repeat with another spatula of nickel(II)carbonate. _________________________________________________________________________ ________________________________________________________________________[2] Word equation with state symbols: _______________________________________________________________________[2] Balanced equation: _______________________________________________________________________[1]

Mr Singh

Acid Reactions

1202P

Making Copper Sulphate Crystals - Practical Acid + Base

Salt + Water

The method is described in the box below.

Pour 25cm of 1M sulphuric acid into a 3 beaker and warm. Add a heaped 100 cm spatula full of copper (II) oxide and stir for 5 minutes.

Filter the hot solution into an evaporating basin. This removes the excess copper (II) oxide.

Put the evaporating basin over a steam bath and heat until crystals start to form around the edge. Leave to cool and then place the basin on a shelf overnight.

Questions: • • • • •

Why must an excess of copper oxide be taken? Why is the solution filtered? Why is better to use a steam bath than heat the evaporating basin directly? In terms of bonding, describe what happens to both a copper ion and an oxide ion during this process. Apart from non-soluble bases, what other type of compounds could be used to make a salt using this method?

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Acid Reactions

Making Sodium Chloride by Titration Introduction In this experiment the alkali sodium hydroxide is neutralised with hydrochloric acid to produce the soluble salt sodium chloride. This is then concentrated and crystallised in a crystallising dish.

Safety Wear eye protection. Method 1. Add 25 cm3 of sodium hydroxide solution, NaOH (Corrosive), to a conical flask using a pipette (practical before hand, see appendix) and add a couple of drops of methyl orange indicator. 2.

Fill the burette with hydrochloric acid, HCl and run through to the zero mark (use a funnel to fill the burette and a beaker to collect the excess acid).

Add the hydrochloric acid to the sodium hydroxide solution in small volumes swirling after each addition. Continue until the solution turns to a light pink and record this reading on the burette to 2 d.p.

Page 1 of 3 Mr Singh

Acid Reactions

Repeat titration till you have two readings 0.1cm3 apart. Calculate the mean titre (amount added from the burrette) to 1 d.p.

Carefully add this volume of fresh hydrochloric acid to another 25 cm3 of sodium hydroxide solution to produce a neutral solution without indicator.

Reduce to about half the volume using an evaporating dish on a gauze over a Bunsen burner flame.

Leave to evaporate in a crystallising dish to produce a white crystalline solid.

Results Record all results to the nearest Âą 0.05cm3 Trial

1st titration

2nd titration

3rd titration

Final burette reading/cm3 Initial burette reading/cm3 Titre/cm3

Mean Titre/cm3

Questions 1.

What is the everyday name for sodium chloride?

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Acid Reactions

This reaction is a specific example of the general reaction: Acid + alkali â&#x2020;&#x2019; salt + water. Write a word equation for this specific reaction.

Write a formula equation for this reaction.

Why must you use another 25 cm3 of sodium hydroxide solution to make pure sodium chloride?

Appendix Pipette practice Pipette in 25cm3 of water into a conical flask on a balance and record the mass. 1st run

2nd run

3rd run

Final mass/g Initial mass/g Mass of aliquot/g Largest difference in readings/g

Page 3 of 3

Mr Singh

Run 1

Run 2

Run 3

Run 4

9. What is the approximate concentration of your Unknown solution ………………………………………………………………………………

8. What was the volume of acid used in each Run? ……………….

7. Which Unknown did you use? ………………………………………

6. What was the average value for the titration? ……………………

………………………………………………………………………………

Questions 1. Colour of indicator initially (in acid) ………………………………… 2. Colour of indicator at end (in alkali) ……………………………….. 3. Why do we use a white tile under the conical flask? ……………………………………………………………………………… ……………………………………………………………………………… 4. Why do we swirl the mixture while the alkali is being added from the burette? ……………………………………………………………………………… ……………………………………………………………………………… 5. What was the concentration of the Sodium hydroxide solution?

Average Titre (cm3)

Titre (cm3)

Initial Reading (cm3)

Final Reading(cm3)

Results

Titration 1

Equipment List • Burette, burette stand & holder • 25 cm3 measuring cylinder • Phenolphthalein solution • Unknown solution of Acid (A) or (B) • 0.2 mol dm-3 Sodium hydroxide (NaOH) • funnel • 100 cm3 beaker • white tile • 100 cm3 conical flask Procedure 1. Place burette holder on stand and clamp securely – make sure the tap is closed 2. Place the stand on the floor or chair so the top of the burette is at eye level and place the funnel in the end 3. Carefully pour the solution of known concentration (NaOH) into the burette above the zero level 4. Place the burette stand back on the table and place the beaker underneath the tap 5. Slowly turn the tap to release the excess NaOH – watch the level as you do this and stop the tap when the meniscus rests on zero. Remove the beaker 6. Place 10 cm3 of the unknown solution of acid into the conical flask using the measuring cylinder 7. Add a few drop of phenolphthalein indicator to the flask and place under the tap on a white tile 8. Gently turn the tap of the burette so NaOH is added dropwise into the flask 9. Swirl the mixture during the experiment 10. When the solution changes colour stop the tap and record the value on the burette in the Final reading for Run 1 AND the Initial reading for Run 2 11. Rinse the conical flask with water and repeat the experiment again from Number 6. – conduct 4 Runs in total 12. Take the average of the concordant results – highlight which results were used.

1805P

Acid Reactions

Mr Singh