Reactions of metals with dilute acids
2 marks · EasyA student uses 0.35 g of magnesium in a reaction with excess dilute hydrochloric acid. (Relative atomic mass, Mg = 24)
Calculate the number of moles of magnesium used. Give your answer to two decimal places.
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0.35 / 24 = 0.0146... so 0.015 mol (2 dp) mol (±0.001)
Must show: Clear working: n = mass / Ar
Also accept: 0.0146 mol; 0.01458 mol
Common mistakes: Dividing Ar by mass
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Marking points
M1 · 1 mark · Applies correct formula: moles = mass / relative atomic mass.
A1 · 1 mark · Final answer correct to two decimal places: 0.015 mol.
Worked solution
Moles = mass / Ar = 0.35 g / 24 = 0.01458...
Rounded to 2 decimal places = 0.015 mol