Skip to content

Course home

Monitoring chemical reactions

Monitoring chemical reactions

EasyMediumHard
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556
Question 2

A student monitors the rate of the acid-catalysed iodination of propanone:

CH3COCH3(aq)+I2(aq)→H+(aq)CH3COCH2I(aq)+H+(aq)+I−(aq) \text{CH}_3\text{COCH}_3(\text{aq}) + \text{I}_2(\text{aq}) \xrightarrow{\text{H}^+(\text{aq})} \text{CH}_3\text{COCH}_2\text{I}(\text{aq}) + \text{H}^+(\text{aq}) + \text{I}^-(\text{aq}) CH3​COCH3​(aq)+I2​(aq)H+(aq)​CH3​COCH2​I(aq)+H+(aq)+I−(aq)

The student withdraws 10.0 cm3 samples of the reaction mixture at regular time intervals. Each sample must be immediately quenched before titrating the remaining iodine against standard sodium thiosulfate solution.

Which of the following is the most suitable quenching agent to immediately stop this reaction?

A

Sodium hydrogencarbonate, to neutralise the H+\text{H}^+H+ catalyst

B

Sodium thiosulfate, to react with the remaining I2\text{I}_2I2​

C

Starch solution, to bind and stabilise the iodine molecules

D

Ice-cold water, to cool and dilute the reaction mixture

Markscheme

Monitoring chemical reactions Questions

  1. GCSE
  2. /Chemistry
  3. /Monitoring chemical reactions

91 exam-style questions on OCR GCSE Chemistry Monitoring chemical reactions. Each one has a worked solution and a mark scheme showing where the marks go.

Question bank