AQA GCSE Chemistry (8462), Higher tier · Bonding, structure and the properties of matter › Bonding, structure and properties
Practise State symbols. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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State symbols show the states of the substances in a chemical equation. What does the state symbol (aq) mean?
aqueous: dissolved in water
Calcium carbonate decomposes when heated to form calcium oxide and carbon dioxide. Add state symbols to the equation. CaCO3(....) → CaO(....) + CO2(....)
CaCO3(s) → CaO(s) + CO2(g)
Methane burns in a gas cooker flame. CH4 + 2O2 → CO2 + 2H2O In the flame, the water is produced as a gas. Add state symbols to the equation.
CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
When solutions of silver nitrate and potassium iodide are mixed, a yellow precipitate of silver iodide, AgI, forms. Write the ionic equation for this reaction, including state symbols.
Ag+(aq) + I−(aq) → AgI(s)
Write a balanced symbol equation for this reaction, including state symbols.
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
State symbols show the states of the substances in a chemical equation.
(a) What does the state symbol (aq) mean?[1]
(b) Give the state symbol for water at room temperature.[1]
(c) Complete the state symbols in the equation for the reaction of magnesium with hydrochloric acid. Mg(s) + 2HCl(....) → MgCl2(....) + H2(....)[2]
Show the answer and mark scheme
(a)Answer: aqueous: dissolved in water
aqueous / dissolved in water
(b)Answer: (l)
(l)
(c)Answer: HCl(aq), MgCl2(aq), H2(g)
HCl(aq) and MgCl2(aq)
H2(g)
Question 2Medium6 marks
Chemical equations should include state symbols.
(a) Calcium carbonate decomposes when heated to form calcium oxide and carbon dioxide. Add state symbols to the equation. CaCO3(....) → CaO(....) + CO2(....)[1]
(b) Add state symbols to the equation for the reaction of sodium with water. 2Na(....) + 2H2O(....) → 2NaOH(....) + H2(....)[2]
(c) When solutions of barium chloride and sodium sulfate are mixed, a white precipitate of barium sulfate forms. Add state symbols to the equation. BaCl2(....) + Na2SO4(....) → BaSO4(....) + 2NaCl(....)[2]
(d) In the electrolysis of molten sodium chloride, the sodium chloride is shown as NaCl(l), not NaCl(aq). Explain why.[1]
(d)Answer: Molten means melted (a pure liquid); it is not dissolved in water.
molten means melted / liquid, not dissolved in water
Question 3Hard7 marks
This question is about state symbols in equations.
(a) Write a balanced symbol equation, including state symbols, for the reaction of lithium with water. Lithium hydroxide is soluble in water.[3]
(b) A student wrote the state symbol for the sodium chloride in salt water as NaCl(l). Explain why this is wrong.[2]
(c) When solutions of silver nitrate and potassium iodide are mixed, a yellow precipitate of silver iodide, AgI, forms. Write the ionic equation for this reaction, including state symbols.[2]
Show the answer and mark scheme
(a)Answer: 2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
correct formulae: Li + H2O → LiOH + H2
balanced: 2Li + 2H2O → 2LiOH + H2
state symbols: (s), (l), (aq), (g)
(b)Answer: The sodium chloride is dissolved in water, so it should be (aq); (l) would mean molten sodium chloride, which only exists above 801 °C.
sodium chloride is dissolved in water so it should be (aq)
(l) means molten / pure liquid sodium chloride (which only exists at very high temperatures)