CAIE A-Level Chemistry AS 2.4 Reacting Masses and Volumes of Solutions and Gases Questions

Practise multistep stoichiometry with masses, solution concentrations, gas volumes, yields and limiting reagents.

Exam points

convert the known quantity to moles and apply the balanced-equation mole ratio before changing units
test each reactant against the stoichiometric requirement to identify limiting and excess reagents
retain unrounded working values and report the final result to justified significant figures with units

Covered syllabus points

[Maximum number: 1]

Sample X is added to water and made up to a total volume of $200 \mathrm{~cm}^{3}$ . This gives a solution of $0.100 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}$ .

What is X ?

$10 \mathrm{~cm}^{3}$ of $1.00 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}$

$30 \mathrm{~cm}^{3}$ of $0.90 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}$

$50 \mathrm{~cm}^{3}$ of $0.40 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}$

$100 \mathrm{~cm}^{3}$ of $0.30 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}$

[Maximum number: 1]

A mixture of $10 \mathrm{~cm}^{3}$ of methane and $10 \mathrm{~cm}^{3}$ of ethane was sparked with an excess of oxygen. After cooling, the residual gas was passed through aqueous potassium hydroxide.

All gas volumes were measured at the same temperature and pressure.
Which volume of gas was absorbed by the alkali?

$15 \mathrm{~cm}^{3}$

$20 \mathrm{~cm}^{3}$

$30 \mathrm{~cm}^{3}$

$40 \mathrm{~cm}^{3}$

[Maximum number: 1]

A piece of rock has a mass of 2.00 g . It contains calcium carbonate, but no other basic substances. It neutralises exactly $36.0 \mathrm{~cm}^{3}$ of $0.500 \mathrm{~mol} \mathrm{dm}^{-3}$ hydrochloric acid.

What is the percentage by mass of calcium carbonate in the 2.00 g piece of rock?

22.5 %

45.0 %

72.0 %

90.1 %

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Covered syllabus points

Question 1

Question 2

Question 3