What are catalysts?
4 marks · NormalWrite a word equation and a balanced symbol equation for the catalytic decomposition of hydrogen peroxide.
Explain why manganese(IV) oxide is described as a catalyst in this reaction.
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(a) hydrogen peroxide → water + oxygen 2H2O2(aq) → 2H2O(l) + O2(g) · must show Correct word equation, Correct balanced symbol equation with state symbols
(b) Manganese(IV) oxide speeds up the decomposition without being used up or chemically changed by the end of the reaction. · must show Speeds up reaction, Not consumed or remains unchanged
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Marking points
B1 (a) · 1 mark · Correct word equation: hydrogen peroxide → water + oxygen.
B2 (a) · 1 mark · Correct balanced symbol equation: 2H2O2(aq) → 2H2O(l) + O2(g).
B3 (b) · 1 mark · States that manganese(IV) oxide speeds up the reaction (acts as catalyst).
B4 (b) · 1 mark · States that it remains chemically unchanged/not used up.
Worked solution
(a) Word equation: hydrogen peroxide → water + oxygen
(b) Manganese(IV) oxide speeds up the decomposition of hydrogen peroxide but is not used up in the reaction, as its mass remains unchanged.