Purity and separating mixtures

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Question 33
Medium

A student has a sample of a liquid.

a.

State a method the student uses to find out if the sample is pure.

[1]
b.

The student finds out that the sample is a mixture containing octane, C8H18\text{C}_8\text{H}_{18}C8​H18​, and cyclooctane, C8H16\text{C}_8\text{H}_{16}C8​H16​.

What is the empirical formula of octane?

[1]
c.

The boiling point of octane is lower than the boiling point of cyclooctane.

Describe a method the student could use to obtain a sample of pure octane from the mixture of cyclooctane and octane.

[2]
d.

The student obtains 10.5 g10.5\text{ g}10.5 g of octane from 13.8 g13.8\text{ g}13.8 g of the mixture of octane and cyclooctane.

Calculate the percentage of octane obtained. Give your answer to 222 significant figures.

[2]
e.

Octane reacts with oxygen in a combustion reaction.

Complete the balanced symbol equation for this reaction:

2C8H18+□ O2→□ CO2+□ H2O2\text{C}_8\text{H}_{18} + \Box\,\text{O}_2 \rightarrow \Box\,\text{CO}_2 + \Box\,\text{H}_2\text{O}2C8​H18​+□O2​→□CO2​+□H2​O

[2]

Purity and separating mixtures Questions

  1. GCSE
  2. /Chemistry
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