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Question 1

This question is about carboxylic acids.

Compound E is a trans stereoisomer of an unsaturated organic acid with the general formula CnH2n−1COOH\text{C}_n\text{H}_{2n-1}\text{COOH}Cn​H2n−1​COOH.

A student plans to analyse acid E by carrying out a titration.

a.

A student first prepares 250.0 cm3250.0\text{ cm}^3250.0 cm3 of a standard solution of 0.150 mol dm−30.150\text{ mol dm}^{-3}0.150 mol dm−3 NaOH\text{NaOH}NaOH for the titration.

The student is provided with solid NaOH\text{NaOH}NaOH and usual laboratory apparatus and equipment.

Describe how the student would prepare the standard solution, giving full details of quantities, apparatus and method.

[5]
b.

The student prepares a 250.0 cm3250.0\text{ cm}^3250.0 cm3 solution containing 3.600 g3.600\text{ g}3.600 g of acid E.

The student titrates 25.0 cm325.0\text{ cm}^325.0 cm3 samples of the solution of E with the prepared 0.150 mol dm−30.150\text{ mol dm}^{-3}0.150 mol dm−3 NaOH(aq)\text{NaOH(aq)}NaOH(aq) in the burette.

1 mol NaOH1\text{ mol NaOH}1 mol NaOH reacts with 1 mol1\text{ mol}1 mol of E.

The mean titre of NaOH(aq)\text{NaOH(aq)}NaOH(aq) is 24.00 cm324.00\text{ cm}^324.00 cm3.

Analyse the titration results to determine two possible structures for the trans stereoisomer of organic acid E.

[7]
Markscheme

Planning Questions

  1. A Level
  2. /Chemistry
  3. /Planning

3 exam-style questions on OCR A A Level Chemistry Planning. Each one has a worked solution and a mark scheme showing where the marks go.

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