CAIE IGCSE Chemistry 3. Stoichiometry Question Bank

Practise using formulae, equations, relative masses and mole relationships to interpret reactions and calculate chemical amounts.

Covered syllabus points

3.1 Formulae 3.2 Relative masses of atoms and molecules 3.3 The mole and the Avogadro constant

[Maximum number: 3]

The Haber process is used to manufacture ammonia.

(a)

Ammonia reacts with an acid to form ammonium sulfate, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}$ .

[ 3 ]

(i)

State the formula of the acid used.

[ 1 ]

$\mathrm{H}_{2}\mathrm{SO}_{4}$ }

(ii)

Calculate the percentage composition by mass of nitrogen in $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}$ .
percentage of nitrogen =

[ 2 ]

M1 $M_{r}$ of $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}=132$ (1)

M2 $2 \times 14=28$ and $\% \mathrm{~N}=100 \times 28 / 132=21.2 \%(1)$

Question

Marks

[Maximum number: 4]

This question is about elements X, Y and Z.

(a)

An atom of element X is represented as ${ }_{16}^{34} \mathbf{X}$ .

[ 1 ]

(i)

Suggest the formula of the compound formed between aluminium and X.

[ 1 ]

$\mathrm{A} l_{2} \mathrm{X}_{3}$

(b)

Identify the atom against which the relative masses of all other atoms are compared.

[ 1 ]

${ }^{12} \mathrm{C}$

(c)

What is the name of the amount of any substance that contains $6.02 \times 10^{23}$ particles?

[ 1 ]

(d)

The constant $6.02 \times 10^{23}$ has a name.

What is the name of this constant?

[ 1 ]

[Maximum number: 1]

The chemical formulae of two substances, W and X, are given.
W $\mathrm{NaAlSi}_{3} \mathrm{O}_{8}$
X $\quad \mathrm{CaAl}_{2} \mathrm{Si}_{2} \mathrm{O}_{8}$
Which statements are correct?

1 W and X contain the same amount of oxygen.
2 W contains three times as much silicon as X.
3 X contains twice as much aluminium as W.
A1 and 2
B1 and 3
C 2 and 3
D 1, 2 and 3

[Maximum number: 1]

What is the relative molecular mass, $M_{\mathrm{r}}$ , of sulfur dioxide?

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Covered syllabus points

3. Stoichiometry question 1

Question (a)

Question (i)

Question (ii)

3. Stoichiometry question 2

Question (a)

Question (i)

Question (b)

Question (c)

Question (d)

3. Stoichiometry question 3

3. Stoichiometry question 4