Cambridge IGCSE · Chemistry (0620)

Relative masses of atoms and molecules: Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Relative masses of atoms and molecules.

10 questions23 marksFree, no account

Question 1

1 mark

Which statement best describes the relative atomic mass, \( A_r \), of an element?

Question 2

1 mark

Calcium oxide reacts with carbon dioxide to form calcium carbonate according to the equation:
\( CaO + CO_2 \rightarrow CaCO_3 \)
Using simple proportions, what mass of calcium carbonate is produced from \( 14g \) of calcium oxide?
(Relative formula masses: \( CaO = 56, CaCO_3 = 100 \))

Question 3

1 mark

An element X has two isotopes with mass numbers 107 and 109. If the relative atomic mass of X is 107.8, what is the percentage abundance of the isotope with mass number 107?

Question 4

1 mark

What is the relative molecular mass, \( M_r \), of ethane, \( C_2H_6 \)?
(Relative atomic masses: \( C = 12, H = 1 \))

Question 5

1 mark

A sample of element Boron contains two isotopes, \( ^{10}B \) and \( ^{11}B \). The abundance of \( ^{10}B \) is \( 20\% \) and the abundance of \( ^{11}B \) is \( 80\% \).
Calculate the relative atomic mass of Boron.

Question 6

2 marks

Define relative molecular mass, \(M_r\), with reference to the carbon-12 isotope.

Write your answer out first, then check it against the worked solution.

Question 7

3 marks

Calculate the total mass of products formed when \(4.0\text{ g}\) of calcium reacts completely with \(1.6\text{ g}\) of oxygen, based on the principle of conservation of mass.

Write your answer out first, then check it against the worked solution.

Question 8

6 marks

The element copper exists as two isotopes, \(^{63}Cu\) and \(^{65}Cu\). If the relative atomic mass of copper is \(63.5\), calculate the percentage abundance of the lighter isotope.

Write your answer out first, then check it against the worked solution.

Question 9

3 marks

(a) Define relative molecular mass, \(M_r\).

(b) Calculate the relative formula mass of hydrated aluminium sulfate, \(Al_2(SO_4)_3 \cdot 18H_2O\).
(Relative atomic masses: Al = 27, S = 32, O = 16, H = 1)

Write your answer out first, then check it against the worked solution.

Question 10

4 marks

A metal \( X \) forms an oxide with the formula \( X_2O_3 \). It is found that 1.08 g of the metal reacts completely with oxygen to form 2.04 g of the oxide.

(a) Calculate the mass of oxygen present in the 2.04 g sample of the oxide.
(b) Use the mass ratio and the known relative atomic mass of oxygen to calculate the relative atomic mass, \( A_r \), of metal \( X \).
(c) Identify the metal \( X \) using the Periodic Table.

(Relative atomic mass: \( O = 16.0 \))

Write your answer out first, then check it against the worked solution.

* The content provided by thinka is generated by AI and may not always be accurate or up-to-date. Please use it as a supplementary resource and verify with official materials.

You've seen the model answer. Now get yours marked.

This page can show you how a good answer looks. It cannot tell you what your answer was missing. thinka marks your written work against the real mark scheme in about 15 seconds.

Get My Answers Marked Back to the notes

Want more questions like these? Get a fresh set on this topic, graded as you go.