CAIE IGCSE Chemistry 3.3 The Mole and t…Constant

Covered syllabus points

3.3.1—Concentration can be measured in g/dm3 3.3.2—Mole, mol, is the unit of amount of 3.3.3—Amount of substance relation: amount 3.3.4—Molar gas volume, taken as 24 dm3 at 3.3.5—Stoichiometric reacting masses 3.3.6—Experimental data from a titration to 3.3.7—Empirical formulae and molecular 3.3.8—Percentage yield, percentage

[Maximum number: 1]

Benzene is a liquid with molecular formula $\mathrm{C}_{6} \mathrm{H}_{6}$ .
Ethene is a gas with molecular formula $\mathrm{C}_{2} \mathrm{H}_{4}$ .
Which statement is correct?

1 mole of benzene and 1 mole of ethene contain the same number of atoms.

1 mole of benzene and 1 mole of ethene both have a volume of $24 \mathrm{dm}^{3}$ at room temperature and pressure.

Both benzene and ethene have the same empirical formula.

The number of carbon atoms in 0.5 moles of ethene is equal to the Avogadro constant.

[Maximum number: 1]

Magnesium chloride, $\mathrm{MgCl}_{2}$ , contains magnesium ions and chloride ions.
How many chloride ions are present in two moles of magnesium chloride?

$6.02 \times 10^{23}$

$1.204 \times 10^{24}$

$2.408 \times 10^{24}$

$3.612 \times 10^{24}$

[Maximum number: 1]

What is the volume of 14.5 g of gaseous butane, $\mathrm{C}_{4} \mathrm{H}_{10}$ , at room temperature and pressure?

$96.0 \mathrm{~cm}^{3}$

$6.0 \mathrm{~cm}^{3}$

$96.0 \mathrm{dm}^{3}$

$6.0 \mathrm{dm}^{3}$

[Maximum number: 1]

The concentration and volume of an aqueous alkali are known.

Which additional information is required to calculate the number of moles of acid needed to neutralise the aqueous alkali?

the concentration of the acid

the equation for the acid-alkali reaction

the formula of the acid

the volume of the acid required for neutralisation

[Maximum number: 1]

The concentration of a sample of dilute aqueous sodium hydroxide is found by titration.
The apparatus used is shown.

Figure for Question 5 — CAIE IGCSE Chemistry

Which information is needed to calculate the concentration of the dilute aqueous sodium hydroxide in $\mathrm{mol} / \mathrm{dm}^{3}$ ?

concentration
of HCl

volume of
HCl used

molar mass
of HCl

volume of
NaOH used

molar mass
of NaOH

✓

$\chi$

✓

$\chi$

$\boldsymbol{\chi}$

✓

$\boldsymbol{\chi}$

✓

$\boldsymbol{\chi}$

✓

key
✓ = needed
x = not needed

[Maximum number: 4]

Hydrated cobalt(II) sulfate, $\mathrm{CoSO}_{4} \cdot \mathrm{x} \mathrm{H}_{2} \mathrm{O}$ , produces water when it is heated.

\mathrm{CoSO}_{4} \cdot \mathrm{xH}_{2} \mathrm{O}(\mathrm{~s}) \rightarrow \mathrm{CoSO}_{4}(\mathrm{~s})+\mathrm{xH}_{2} \mathrm{O}(\mathrm{~g})

A student does an experiment to determine the value of x in $\mathrm{CoSO}_{4} \cdot \mathbf{x} \mathrm{H}_{2} \mathrm{O}$ .
step 1 The student weighs a sample of hydrated cobalt(II) sulfate.
step 2 The student heats the sample of hydrated cobalt(II) sulfate.
step 3 The student weighs the remaining solid after heating.

In an experiment, 1.405 g of $\mathrm{CoSO}_{4} \cdot \times \mathrm{H}_{2} \mathrm{O}$ is heated until all the water is given off.

The mass of $\mathrm{CoSO}_{4}$ that remains is 0.775 g .
$\left[M_{\mathrm{r}}: \mathrm{CoSO}_{4}, 155 ; \mathrm{H}_{2} \mathrm{O}, 18\right]$
Determine the value of x using the following steps.
- Calculate the number of moles of $\mathrm{CoSO}_{4}$ that remains. mol
- Calculate the mass of $\mathrm{H}_{2} \mathrm{O}$ given off. g
- Calculate the number of moles of $\mathrm{H}_{2} \mathrm{O}$ given off. mol
- Determine the value of x.

\begin{array}{r} x=\ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots . . . . \\ {[4]} \\ {[T o t a l: 17]} \end{array}

M1 $0.005 / 5 \times 10^{-3}(1)$

M2 0.63 (1)

M3 (0.63 / 18 =) 0.035 (1)

M4 $(0.035 \div 0.005=) 7(1)$

[Maximum number: 1]

When heated, copper(II) oxide, CuO , reacts with ammonia, $\mathrm{NH}_{3}$ .

3 \mathrm{CuO}+2 \mathrm{NH}_{3} \rightarrow 3 \mathrm{Cu}+\mathrm{N}_{2}+3 \mathrm{H}_{2} \mathrm{O}

8.5 g of ammonia reacts with an excess of copper(II) oxide to produce 26.4 g of copper.

What is the percentage yield of copper in this reaction?

27.5%

32.2\%

55.0\%

82.5\%

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CAIE IGCSE Chemistry 3.3 The Mole and the Avogadro Constant Topic Practice

Covered syllabus points

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7