CPAC A5: following the rate of iodine propanone reaction by a titrimetric method

Question 1

propanone reacting with iodine consideration

Answer 1

ACIDIC SOLUTION. (sulphuric acid catalyst)

Question 2

method

Answer 2

• add known vol and conc propanone and acid to a beaker
• add iodine and swirl. immediately start stopclock
• use 10cm3 pipette to withdraw sample of mixture and transfer to conical flask containing sodium hydrogen carbonate (quenches reaction)
• record time whenHALF contents pipette added
• titrate against sodium thiosulphate. add starch indicator when colour is pale yellow. END POINT IS BLUE TO COLOURLESS
• repeat every 2-3 mins

Question 3

processing results

Answer 3

-plot graph of time against vol titre of sodium thiosulphate- its PORPOTIONAL to conc of iodine , so can give u results
- propanone and acid are in large excess so concentrations are constant

Question 4

order with respect to iodine

Answer 4

0
straight line through the origin

Question 5

factor having effect on rate

Answer 5

-temperature
- carry out in a water bath

Question 6

why time when pipette half empty

Answer 6

• mean time the reaction was quenched, as doesnt empty all reaction mixture in one go

Question 7

order w respect to hydrogen ions

Answer 7

first