IGCSE · Chemistry 0620 · Stoichiometry

Formulae & equations: IGCSE Chemistry questions with answers

Free Formulae & equations questions for IGCSE Chemistry (0620), part of Stoichiometry. Each question has the answer and the marking points an examiner would look for.

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Formulae & equations practice questions

Question 1Multiple choice · 1 markA* challenge

What is the formula of calcium nitrate?

  1. A Ca2NO3
  2. B Ca(NO3)2
  3. C CaNO6
  4. D CaNO3
Show answer

Answer: B

Question 2Multiple choice · 1 markA* challenge

The equation for the complete combustion of an alkane is shown.
C3H8 + xO2 → 3CO2 + 4H2O
What is the value of x?

  1. A 4
  2. B 5
  3. C 6
  4. D 7
Show answer

Answer: B

Question 3Multiple choice · 1 mark

Which term is described by this statement?
“The simplest whole-number ratio of the different atoms or ions in a compound.”

  1. A molecular formula
  2. B group
  3. C empirical formula
  4. D reactivity series
Show answer

Answer: C

Question 4Structured · 1 mark

Write the formula of calcium sulfate.

[1]
Show answers and mark scheme
PartAnswer and marking pointsMarks
CaSO4
CaSO4 B1
1
Question 5Structured · 13 marks

This question is about metal carbonates.

(a)

Write the equation, with state symbols, for the thermal decomposition of zinc carbonate.

[3]
(b)

Describe a test for carbon dioxide and give the result.

[2]
(c)

Calculate the mass of zinc oxide formed when 6.25 g of zinc carbonate is heated to constant mass. [Mᵣ: ZnCO₃, 125; ZnO, 81]

[3]
(d)

Calculate the volume of carbon dioxide produced at r.t.p. when 6.25 g of zinc carbonate decomposes.

[1]
(e)

Sodium carbonate does not decompose when heated in a Bunsen flame. Suggest why, in terms of reactivity.

[1]
(f)

Explain why the student heats the carbonate to constant mass.

[1]
(g)

Zinc oxide is a basic oxide. Write the equation for its reaction with dilute nitric acid.

[2]
Show answers and mark scheme
PartAnswer and marking pointsMarks
(a)ZnCO₃(s) → ZnO(s) + CO₂(g)
correct formulae B1
balanced B1
state symbols B1
3
(b)bubble through limewater; turns milky
limewater B1
turns milky / cloudy B1
2
(c)4.05 g
moles = 6.25/125 = 0.0500 M1
1 : 1 ratio, × 81 M1
4.05 g A1
3
(d)1.20 dm³
0.0500 × 24 = 1.20 dm³ B1
1
(e)carbonates of more reactive metals are more stable
sodium is very reactive so its carbonate is more stable / thermal stability increases with reactivity B1
1
(f)to make sure decomposition is complete
to ensure all the carbonate has decomposed B1
1
(g)ZnO + 2HNO₃ → Zn(NO₃)₂ + H₂O
correct formulae B1
balanced B1
2
Question 6Structured · 4 marks

Write balanced symbol equations for these reactions, including state symbols.

(a)

Magnesium reacts with dilute hydrochloric acid to form magnesium chloride and hydrogen.

[2]
(b)

Methane burns completely in oxygen.

[2]
Show answers and mark scheme
PartAnswer and marking pointsMarks
(a)Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
correct formulae and balancing B1
correct state symbols B1
2
(b)CH₄ + 2O₂ → CO₂ + 2H₂O
correct formulae B1
balanced B1
2

More Stoichiometry questions

Relative masses & the moleConcentration & titration

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Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in