No topics match this filter.
Practise 14 exam-style questions on Typical properties (chemistry only) for AQA GCSE Chemistry. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Give the colour of copper(II) sulfate solution.
Blue
Copper(II) compounds are typically blue or green, an example of transition metals forming coloured compounds. Anhydrous copper(II) sulfate is white, but it turns blue when water is added.
blue
allow pale blue; do not accept green or turquoise
In the Haber process, the iron catalyst can be used for several years before it needs to be replaced.
Explain why the catalyst does not need to be replaced every time ammonia is made.
A catalyst speeds up a reaction but is not used up, because it is not chemically changed by the reaction. So the same iron catalyst can keep speeding up the reaction between nitrogen and hydrogen for years.
Catalysts take part in the reaction but are regenerated at the end, so the same mass of catalyst is present after the reaction as before. In industry the catalyst is eventually replaced only because its surface becomes contaminated or 'poisoned' by impurities.
a catalyst is not used up in the reaction
allow is not chemically changed
so it can keep speeding up the reaction / can be used again and again
allow can be reused
Metal M forms two chlorides with the formulae MCl₂ and MCl₃. Solutions of both chlorides are coloured.
Suggest whether M is a Group 1 metal or a transition metal. Explain your answer.
M is a transition metal. The chloride ion is Cl⁻, so MCl₂ contains M²⁺ ions and MCl₃ contains M³⁺ ions: M forms ions with different charges. Its compounds are also coloured. Group 1 metals only form 1+ ions (formula MCl) and their compounds give colourless solutions.
Work out the charge on M from each formula using Cl⁻. Two different charges and coloured compounds are both typical of transition metals; iron (FeCl₂ and FeCl₃) is a real example.
transition metal
M forms ions with different charges / M²⁺ and M³⁺
allow Group 1 metals only form 1+ ions
M forms coloured compounds
allow Group 1 compounds are white / form colourless solutions
A sample of an iron oxide contains 70.0% iron by mass. The oxide is either iron(II) oxide, FeO, or iron(III) oxide, Fe₂O₃.
Use calculations to identify the oxide.
Relative atomic masses (Ar): Fe = 56, O = 16
Mr of FeO = 56 + 16 = 72
% Fe in FeO = 56 ÷ 72 × 100 = 77.8%
Mr of Fe₂O₃ = (2 × 56) + (3 × 16) = 160
% Fe in Fe₂O₃ = 112 ÷ 160 × 100 = 70.0%
The sample matches 70.0%, so it is iron(III) oxide, Fe₂O₃.
Percentage by mass of an element = (total Ar of that element in the formula ÷ Mr) × 100. Remember to multiply the Ar of iron by 2 for Fe₂O₃. Iron forming two oxides with different compositions is a result of it forming Fe²⁺ and Fe³⁺ ions.
Mr of FeO = 72 and Mr of Fe₂O₃ = 160
both needed
% Fe in FeO = 56 ÷ 72 × 100 = 77.8%
allow 77.7 to 78; allow ecf from incorrect Mr
% Fe in Fe₂O₃ = 112 ÷ 160 × 100 = 70.0%
allow 70; allow ecf from incorrect Mr
the oxide is iron(III) oxide / Fe₂O₃
must be supported by a calculation; allow if only the Fe₂O₃ percentage is calculated and matches 70%
Ready to try the rest? Every answer you write is marked against the mark scheme, so you can see exactly where the marks are.
Hi! Stuck? Ask me for a hint and I’ll help you work it out. Once you’ve checked your answer I can explain exactly where the marks are.
