Reversible reactions in a sealed container
3 marks · NormalExplain, with reasons, why a sealed container is necessary for studying reversible reactions.
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Common mistakes: Ignoring need for constant amounts; Not mentioning equilibrium
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Marking points
M1 · 1 mark · States a sealed container prevents substances from entering or leaving
M2 · 1 mark · Describes why this is important for maintaining constant conditions
A1 · 1 mark · Correctly explains that equilibrium can only be reached if reactants and products are not lost or gained
Worked solution
A sealed container is needed so that no reactants or products enter or leave the reaction mixture. This ensures the amounts of substances remain constant, which is necessary for equilibrium. Without a sealed container, gases or other substances could escape or be added, so the concentrations would change and equilibrium could not be established.