Procedure : It is mainly divided into six parts: 1) Measurement of the mass of potassium iodate (V) 2) Preparation of potassium iodate (V) solution 3) Preparation of sodium thisulphate solution 4) Preparation of sodium thiosulphate solution 5) Preparation of fruit juice 6) Titration between fruit juice and sodium thiosulphate solution 7) Investigation with other fruit juices 8) Investigation of vitamin C with fruits at 50â—ŚC Here are the detailed steps for carrying the above parts: 1) Measurement of the mass of potassium iodate (V) a) A balance was set zero after a 60ml beaker was placed onto it. b) Around 0.6g of potassium iodate(V) was transferred carefully into the bottle in the balance. c) The reading from the balance was recorded in Table 1. d) The potassium iodate(V) was then transferred into a 60ml beaker. 2) Preparation of potassium iodate (V) solution a) Deionized water was added into the 60ml beaker. b) The solution was stirred with a glass rod until the solution the solid potassium iodate(V) was dissolved as much as possible. c) The potassium iodate(V) solution was transferred into the 250ml volumetric flask. d) Distilled water was added until the meniscus reached the 250ml line. e) The flask was shaken upside down to mix the solution with the distilled water. 3) Preparation of sodium thisulphate solution a) A balance was set zero after a 60ml beaker was placed onto it. b) Around 3g of potassium iodate(V) was transferred carefully into the bottle in the balance. c) The reading from the balance was recorded in Table 1. d) The potassium iodate(V) was then transferred into a 60ml beaker. 4) Preparation of sodium thiosulphate solution a) Deionized water was added into the 60ml beaker. b) The solution was stirred with a glass rod until the solution the solid potassium iodate(V) was dissolved as much as possible. c) The sodium thiosulphate solution was transferred into the 250ml volumetric flask. d) Distilled water was added until the meniscus reached the 250ml line. e) The flask was shaken upside down to mix the solution with the distilled water.
5) Preparation of fruit juice a) The fruit was cut into pieces by a knife b) The juice was extracted by pressing the fruits into a beaker through a muslin cloth. c) The juice was transferred to a clean 250ml volumetric flask. e) Distilled water was added until the meniscus reached the 250ml line. f) The flask was shaken upside down to mix the solution with distilled water. g) The fruit juice mixture was transferred into a 250ml beaker. 6) Titration between fruit juice and sodium thiosulphate solution a) 25cm3 of the fruit juice mixture was transferred to a clean conical flask by a clean pipette. b) 25cm3 of the potassium iodate(V) solution mixture which had been prepared was added into the flask and then 5cm3 of potassium iodide. c) The solution was then titrated immediately with sodium thiosulphate solution. d) A few drops of starch solution when the reaction mixture turns to pale yellow. e) Then the mixture was titrated to the end point, which the solution would become colourless. f) The volume of sodium thiosulphate solution used to titrate was recorded in Table 3. reaction mixture turns to yellow
7) Investigation with other fruit juices a) The above steps were repeated using different fruits (orange, lemon, grape, and kiwi) 8) Investigation of vitamin C with fruits at 50â—ŚC. a) Steps 1-5 were repeated b) 25cm3 of the fruit juice mixture was transferred to a clean boiling tube by a clean pipette. c) The boiling tube was placed in a hot water bath at a temperature of 50â—ŚC. d) 25cm3 of the fruit juice mixture was transferred to a clean conical flask from the boiling tube. b) 25cm3 of the potassium iodate(V) solution mixture which had been prepared was added into the flask and then 5cm3 of potassium iodide. c) The solution was then titrated immediately with sodium thiosulphate solution. d) A few drops of starch solution when the reaction mixture turns to pale yellow. e) Then the mixture was titrated to the end point, which the solution would become colourless. f) The volume of sodium thiosulphate solution used to titrate was recorded in Table 3. g)The above steps were repeated using different fruits (orange, lemon, grape, and kiwi)