Pearson Edexcel IAL Chemistry 1.7 Reacting mass calculations

Practise using balanced equations, molar masses and experimental masses to find products, excess reagents and mixture composition.

Exam points

calculate maximum product mass from a limiting reactant and a balanced equation
compare reactant mole amounts to state which reagent is in excess
use mass change or precipitate mass to find composition or solution concentration

[Maximum number: 1]

This question is about magnesium, magnesium oxide and magnesium sulfate.

Hydrated crystals of magnesium sulfate, $\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}$ , can be made by reacting magnesium with sulfuric acid.

In an experiment, magnesium was added to $30.0 \mathrm{~cm}^{3}$ of $0.500 \mathrm{~mol} \mathrm{dm}^{-3}$ sulfuric acid.
$\left[M_{\mathrm{r}}\right.$ value: $\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}=246.4 \quad A_{\mathrm{r}}$ value: $\left.\mathrm{Mg}=24.3\right]$

Calculate the mass of magnesium needed to react with the sulfuric acid.

mass of Mg

Example of calculation
$0.015 / 1.5 \times 10^{-2} \times 24.3=0.3645(\mathrm{~g})$

Ignore SF except 1SF

TE on (e)(i).

(1)

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1.7—Chemical equations to calculate reacting masses and vice versa question 1