L04 · 3.1.2.1, 3.1.2.2

Moles, particles and relative masses

Exam conditions

Want proof rather than practice? Try 3 unseen questions alone, one mixed in from an earlier unit, then fix each mark you lose. About 14 minutes.

Start the exam questions The lesson for this unit

3 marksCore chemistry3.1.2.1, 3.1.2.2

A cylinder contains 0.500 mol of carbon dioxide. The Avogadro constant

L = 6.022 \times 10^{23}\ \mathrm{mol^{-1}}

(a)

Calculate the mass of carbon dioxide in the cylinder.

[1 mark]

(b)

Calculate the number of molecules in the cylinder.

[1 mark]

(c)

Calculate the total number of atoms in the cylinder.

[1 mark]

3 marksCore chemistry3.1.2.1, 3.1.2.2

Relative masses are measured on the carbon-12 scale.

(a)

Define the term relative atomic mass.

[2 marks]

(b)

Hydrated copper(II) sulfate is

\mathrm{CuSO_4 \cdot 5H_2O}

. Calculate its relative formula mass.

[1 mark]

3 marksCore chemistry3.1.2.1, 3.1.2.2

A student dissolves 5.00 g of calcium chloride,

\mathrm{CaCl_2}

, in water. The Avogadro constant

L = 6.022 \times 10^{23}\ \mathrm{mol^{-1}}

(a)

Calculate the amount, in moles, of

\mathrm{CaCl_2}

[1 mark]

(b)

Calculate the number of chloride ions in the solution.

[2 marks]

4 marksUnfamiliar context3.1.2.1, 3.1.2.2

Caffeine has the molecular formula

\mathrm{C_8H_{10}N_4O_2}

. A cup of coffee contains about 90 mg of it. The Avogadro constant

L = 6.022 \times 10^{23}\ \mathrm{mol^{-1}}

(a)

Calculate the mass, in kg, of one caffeine molecule.

[2 marks]

(b)

Calculate the number of nitrogen atoms in 1.00 mg of caffeine.

[2 marks]

4 marksUnfamiliar context3.1.2.1, 3.1.2.2

A jeweller plates a ring with 2.50 mg of silver. The Avogadro constant

L = 6.022 \times 10^{23}\ \mathrm{mol^{-1}}

(a)

Calculate the number of silver atoms in the plating.

[2 marks]

(b)

Without a full calculation, explain which contains more atoms: 1.00 g of helium or 1.00 g of carbon.

[2 marks]