Cambridge IGCSE · Chemistry (0620)

Formulae: Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Formulae.

10 questions23 marksFree, no account

Question 1

1 mark

Which statement correctly defines the molecular formula of a compound?

Question 2

1 mark

A compound contains only the ions \(Fe^{3+}\) and \(O^{2-}\). What is the correct chemical formula for this ionic compound?

Question 3

1 mark

When aqueous silver nitrate, \(AgNO_{3}(aq)\), is added to aqueous sodium chloride, \(NaCl(aq)\), a white precipitate of silver chloride forms.

Which of the following is the correct ionic equation for this reaction, including state symbols?

Question 4

1 mark

What is the chemical formula for the ionic compound ammonium sulfate?

Question 5

1 mark

An ionic compound is formed between aluminium ions, \(Al^{3+}\), and sulfide ions, \(S^{2-}\).

What is the correct formula for this compound?

Question 6

2 marks

State the definition of the molecular formula of a compound.

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

Question 7

4 marks

Construct the balanced ionic equation, including state symbols, for the reaction between aqueous silver nitrate and aqueous potassium iodide.

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Question 8

5 marks

A compound contains \(52.2\%\) carbon, \(13.0\%\) hydrogen, and \(34.8\%\) oxygen by mass. Determine its empirical formula.
\((A_r: C=12.0, H=1.0, O=16.0)\)

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Question 9

3 marks

Construct the chemical formulae for the following ionic compounds by considering the charges on the ions:
(a) Sodium phosphate
(b) Calcium nitrate
(c) Iron(III) hydroxide

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

Question 10

4 marks

An oxide of iron is formed by reacting \(2.24\text{ g}\) of iron with excess oxygen. The resulting compound has a mass of \(3.20\text{ g}\).
(a) Determine the mass of oxygen that reacted with the iron.
(b) Calculate the empirical formula of this iron oxide.
(Relative atomic masses: Fe = 56, O = 16)

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

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