C1.9a Making limewater Copper carbonate decomposes easily on heating but much more heat is needed to decompose calcium carbonate. When heated strongly for several minutes, it forms calcium oxide. It would be dangerous to add water to powdered calcium oxide, but water can be added more safely to the lump of calcium oxide formed from heating a marble chip. You are going to investigate the reaction between water and calcium oxide, and the properties of the solution formed.
Apparatus eye protection
gauze mat
filter funnel and paper
teat pipette
heat resistant mat
test tube
boiling tube
marble chip
Bunsen burner
test-tube rack
tongs
clean drinking straw
tripod
crucible
spatula
universal indicator
Health and safety ●
Wear eye protection
●
Calcium oxide is CORROSIVE and causes burns.
●
Calcium hydroxide and its solution (limewater) will cause irritation if they get into your eyes.
Method A Put the gauze mat onto the tripod. Put a marble chip on a corner of the gauze mat and heat strongly from below for 10 minutes using the blue flame from the Bunsen burner. Record your observations as the marble chip is heated. B Turn the Bunsen burner off and let the solid cool for 2 minutes. Record its appearance. C Use the tongs to put the solid into the crucible. Cautiously add a few drops of water from the teat pipette. Record your observations. D Use the spatula to scrape some of the material from the crucible into a test tube. You do not need to collect all the material, and you should avoid touching it. Record your observations. E Half fill the test tube with water. Shake the test tube gently to dissolve some of the material. F
Filter the mixture from step E into the boiling tube. Use a clean drinking straw to blow gently into the liquid. Add a few drops of universal indicator. Record your observations.
Recording your results 1
Make sure you have recorded your observations from each step. A suitable table will help.
Considering your results/conclusions 2
How can you tell that the marble chip changes chemically during heating?
3
Assuming that you allowed the solid to cool properly at step B, explain the observations at step C.
4
Name the solution formed at step E. Explain how you know what it is.
5
What do the results from the test with universal indicator tell you about the solution?
6
Write equations to describe the reactions observed in the investigation.
Evaluation 7
Compare your results with the results obtained by other students in the class. Describe any differences seen, and suggest reasons for these differences.
© Pearson Education 2010. Edexcel GCSE Science Activity Pack. This document may have been altered from the original.
C1.9b Reducing acidity Calcium carbonate is used by farmers to neutralise excess acidity in the soil. It is also used to remove acidic gases from coal-fired power station chimneys, which reduces harmful emissions. The reaction of calcium carbonate with dilute hydrochloric acid can be used as a model for these reactions. You are going to investigate what happens to the pH of dilute hydrochloric acid when calcium carbonate is added to it.
Prediction 1
What will happen to the pH of the acid as calcium carbonate is added to it? Give reasons for your answer.
Apparatus eye protection
stirring rod
100 cm3 beaker
25 cm3 measuring cylinder
dilute hydrochloric acid IRRITANT
powdered calcium carbonate
universal indicator solution
indicator colour chart
spatula
Health and safety ●
Wear eye protection
●
Hydrochloric acid is an IRRITANT. Wash off any spills on skin or clothing with plenty of water.
Method A Use the measuring cylinder to add 25 cm3 of dilute hydrochloric acid to the beaker. B Add a few drops of universal indicator solution to the beaker. Record the colour of the indicator and use the colour chart to determine the pH. Record the pH. D Add a level spatula-full of powdered calcium carbonate to the beaker. Carefully stir the mixture until the fizzing stops. E Record the colour of the indicator and use the colour chart to determine the pH. Record the pH. F
Repeat steps D and E until no more fizzing happens.
Recording your results 2
Draw a suitable table for your results. It should include space to record the number of spatulas of calcium carbonate added (including none at the start), the colour observed and the corresponding pH.
Considering your results/conclusions 3
What happened as you added more calcium carbonate to the acid?
4
Suggest why the fizzing eventually stopped and no more calcium carbonate would disappear when added to the acid.
5
To what extent do the results support your prediction?
Evaluation 6
Compare your results with the results obtained by other students in the class. Describe any differences seen, and suggest reasons for these differences.
7
Suggest how the accuracy of the results could be improved.
© Pearson Education 2010. Edexcel GCSE Science Activity Pack. This document may have been altered from the original.
C1.9c Reactions of calcium compounds Name
Class
Date
Reaction of calcium oxide with water 1
What do you see when calcium oxide reacts with water? _________________________________________________________________
2
Write the word equation for the reaction of calcium oxide with water. Use one of the substances below in your answer: calcium carbonate
carbon dioxide calcium hydroxide
_________________________________________________________________
Precipitation reactions 3
Describe what you see when carbon dioxide is bubbled through calcium hydroxide solution (limewater). _________________________________________________________________
4
Write the word equation for the reaction of carbon dioxide with calcium hydroxide. Use two of the substances below in your answer: calcium carbonate
calcium oxide
water
_________________________________________________________________ 5
Name the precipitate formed in the reaction described in questions 3 and 4. _________________________________________________________________
Soil and power stations 6
Explain why farmers may spray powdered calcium carbonate, calcium oxide or calcium hydroxide over their fields. _________________________________________________________________ _________________________________________________________________
7
Explain why wet, powdered calcium carbonate may be sprayed through the waste gases in the chimney of a coal-fired power station. _________________________________________________________________ _________________________________________________________________
Masses in reactions 8
What happens to the total mass during a chemical reaction? Underline the correct answer below: it goes up
9
it stays the same
it goes down
1 g of carbon dioxide is bubbled into 100 g of a calcium hydroxide solution in a flask. What is the total mass of the substances in the flask after the reaction is complete? _________________________________________________________________
Š Pearson Education 2010. Edexcel GCSE Science Activity Pack. This document may have been altered from the original.
C1.9d Calcium compounds in action Reactions of calcium compounds Use the following information to help you answer question 1. Substance calcium carbonate
2
State
CaCO3
solid
calcium oxide
CaO
solid
water
H2O
liquid
carbon dioxide
CO2
gas
Ca(OH)2
aqueous solution
calcium hydroxide 1
Formula
Write balanced equations for the following reactions. Include state symbols in your equations. a
The thermal decomposition of calcium carbonate.
b
The reaction of calcium oxide with water.
c
The reaction of calcium hydroxide solution with carbon dioxide.
Which one of the reactions in question 1 is a precipitation reaction? Explain your answer.
Conservation of mass 3
Silver nitrate solution reacts with sodium iodide to form a yellow precipitate: AgNO3(aq) + NaI(aq) → AgI(s) + NaNO3(aq) a
What colour is silver iodide?
b
If 1.7 g of silver nitrate reacts completely with 1.5 g of sodium iodide, what is the total mass of silver iodide and sodium nitrate produced?
c
In the reaction described in part b, 2.35 g of silver iodide is produced. What mass of sodium nitrate is produced?
Controlling acidity and harmful emissions 4
Explain how farmers can control soil acidity using calcium compounds.
5
Describe how harmful emissions from coal-fired power stations may be reduced using calcium carbonate.
Extra challenge 6
Balance the equation below, which represents one reaction that can happen in the waste gases from coal-fired power stations: CaCO3
+
SO2
+
© Pearson Education 2010. Edexcel GCSE Science Activity Pack. This document may have been altered from the original.
O2
→
CaSO4
+
CO2