6.5 Reversible reactions
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What is a reversible reaction?
Mark scheme
a reaction where the products can react to form the reactants again
Model answer
A reversible reaction is one in which the products can react to make the original reactants again.
Anhydrous copper sulfate is white. Describe what you would see when water is added, and state one use of this reaction.
Mark scheme
- turns blue (1)
- test for water (1)
Model answer
It turns blue. This is used as a test for water.
The forward reaction in a reversible reaction is exothermic. What can you say about the reverse reaction?
Mark scheme
- it is endothermic (1)
- the same amount of energy is transferred / taken in (1)
Model answer
The reverse reaction is endothermic, and it takes in the same amount of energy as the forward reaction gives out.
Ammonium chloride is heated in a test tube. A white solid forms near the top of the tube. Explain why.
Mark scheme
- ammonium chloride decomposes into ammonia and hydrogen chloride (gases) when heated (1)
- the gases cool at the top and react to form ammonium chloride again (1)
Model answer
Heating decomposes the ammonium chloride into ammonia and hydrogen chloride gases. These cool near the top of the tube and react to form solid ammonium chloride again.
Which symbol shows a reversible reaction?
Choose one answer.
Correct Not quite: the answer is ⇌
Mark scheme
C: ⇌
Model answer
C: ⇌.
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