IB Chemistry SL S1.4 Counting particles by mass: the mole questions

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Question 1

Paper 2Hard10 marks

A laboratory checks a powdered reference blend containing only paracetamol and caffeine. The structures of the two compounds are shown in Figure 1.

ONHOHParacetamolNONNNOCaffeine

A sample of the blend has a mass of 1.6754 g and contains a total amount of 0.01000 mol of molecules. A quality-control note states that the two compounds are present in equal masses.

(a)

Use Figure 1 and the Ar values in the data booklet to determine the molecular formula and Mr of each compound.

[4]
(b)

Determine the amount, in mol, of each compound in the sample. Show your reasoning.

[4]
(c)

Calculate the mass of each compound in the sample and state whether the quality-control note is supported.

[2]

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