Data response Example 7

Data Response question on Compound X

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I have made up this question to help prepare students for the data response questions which appear on Section A of Paper 3 for the examinations on the 2014 programme (i.e. for examinations after May 2016). The information given is new to the students but they should be able to use their knowledge and understanding of the chemistry content of the programme to answer the questions. Because I have tried to make the chemistry interesting it may be a little harder than an actual exam question but exposure to questions like this beforehand should make students able to face the data response question in the final examination with considerable confidence. All the answers require a knowledge and understanding of material from the core only so this particular question is suitable for both Standard and Higher Level students.

As well as including model answers I have also explained the chemistry fully and given the 'Complete course for students' links to the pages which cover the theory behind each individual question. If you set it as an assigned task using Student Access, students will not be able to see the model answers until after they have submitted their answers to you. If you simply give students access to the page (rather than assigning it as a task) they will be able to access the model answers themselves for review/revision/self-study etc.

If you do not wish to use student access, links to downloadable versions of the questions and, separately the worked answers, can be found at Printable versions of written tasks.

Compound X is a crystalline solid that occurs naturally in some fruits.

Analysis of pure Compound X shows that it contains 68.84% carbon, 4.96% hydrogen and 26.20% oxygen by mass.

The mass spectrum of Compound X shows a molecular ion peak with m/z = 122.

The low resolution 1H NMR spectrum of Compound X shows two signals with an integration trace ratio of 5:1.

The infrared spectrum of Compound X shows a broad strong peak between 2500 and 3000 cm-1 and a sharp peak at 1700 cm-1.

(a) (i) Show that the molecular formula of Compound X is C7H6O2. [2]

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(ii) State the information that can be deduced about the structure of Compound X from its 1H NMR spectrum. [2]

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(iii) Deduce the molecular structure of Compound X. [1]

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(b) The value for the acid dissociation constant of Compound X is 6.31 x 10-5. Using HX to represent Compound X, state the equation for the reaction of Compound X with water. [1]

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(c) The following table shows the solubility of Compound X in water at different temperatures:

Suggest how an impure sample of Compound X could be purified in a school laboratory. [1]

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(d) Compound X reacts with propan-1-ol when warmed in the presence of a sulfuric acid catalyst. The inorganic product obtained in this reaction is water.

(i) State the name of the type of reaction that is taking place. [1]

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(ii) Deduce the molecular formula of the organic product. [1]

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