Edexcel IGCSE Chemistry 1.29 Reacting masses

Practise using balanced equations and experimental data to calculate reacting masses, limiting reactants, excess reagents and theoretical yields.

Exam points

use mole ratios from balanced equations to calculate product or reactant masses
show whether a reactant is in excess by comparing required and available amounts
calculate maximum theoretical mass from given masses, Mr values and equations

[Maximum number: 3]

A sample of iron(III) oxide reacts with excess carbon monoxide.

This is the equation for the reaction.

\mathrm{Fe}_{2} \mathrm{O}_{3}+3 \mathrm{CO} \rightarrow 2 \mathrm{Fe}+3 \mathrm{CO}_{2}

Calculate the minimum mass of iron(III) oxide needed to produce a theoretical yield of 28 g of iron.
[for $\mathrm{Fe}_{2} \mathrm{O}_{3} \quad M_{\mathrm{r}}=160$ ]
minimum mass of iron(III) oxide =

M1 (amount of Fe= ) $28 \div 56$ OR 0.5(0)(mol)

M2 (amount of $\mathrm{Fe}_{2} \mathrm{O}_{3}=$ ) $0.5 \div 2$ OR $0.25(\mathrm{~mol})$

M3 (mass of $\mathrm{Fe}_{2} \mathrm{O}_{3}=0.25 \times 160=$ ) $40(\mathrm{~g})$

ALLOW ecf throughout

correct answer without working scores 3

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1.29 Reacting masses question 1