Worksheet with answers

2.2 Relative mass
OCR Chemistry A Follow up sheet

Determining the relative atomic mass
of a metal

Specification references
• 1.1.1 c) • 1.2.1 a) b) c) d) e)
• 1.1.2 b) • 1.2.2 a) k)
• 1.1.3 a) b) c) • 2.1.3 e) (i) (ii) f)
• 1.1.4 a) c) d)

Learning outcomes
After completing the worksheet you should be able to:
• carry out calculations using stoichiometric relationships
• determine the relative atomic mass of a metal by using experimental data
• evaluate different experimental methods to determine the relative atomic mass of
a metal.

Questions
1 a State what is meant by the term ‘relative atomic mass’. (1 mark)
b Use your periodic table to give the relative atomic mass of the following
metals: (3 marks)
• lithium (Li)
• magnesium (Mg)
• chromium (Cr)
• beryllium (Be)
• silver (Ag)
• potassium (K).

2 A student carried out an experiment to determine the relative atomic mass of
calcium. She added 0.40 g of calcium to 100 cm3 of distilled water and collected
the hydrogen formed. On completion of the reaction, she found she had
collected 202 cm3 of hydrogen.
a Construct an equation for this reaction. (1 mark)
b Calculate the number of moles of hydrogen formed. (1 mark)
c Calculate the relative atomic mass of the metal. Quote your answer to one
decimal place. (3 marks)

3 To check her results, the student decided to titrate the solution formed with
hydrochloric acid. She placed 25 cm3 of the solution into a conical flask and
added some phenolphthalein indicator. The solution required 24.20 cm3 of
0.2 mol dm-3 of hydrochloric acid for neutralisation.

© Oxford University Press 2015 www.oxfordsecondary.co.uk/acknowledgements
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