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Reaction kinetics
5 Class 11 Chemistry questions with answers and explanations.
Printable worksheet with answer key
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The rate of a reaction usually increases with temperature because:
- 1 Molecules get larger
- 2 More molecules have enough energy to react
- 3 Activation energy increases
- 4 Pressure falls
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Correct answer: More molecules have enough energy to react
A higher fraction of molecules exceeds the activation energy.
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A catalyst increases rate by:
- 1 Lowering the activation energy
- 2 Raising Kc
- 3 Raising temperature
- 4 Increasing concentration
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Correct answer: Lowering the activation energy
It provides a path with lower activation energy.
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For rate = k [A]^2, doubling [A] changes the rate by a factor of:
- 1 2
- 2 8
- 3 4
- 4 1
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Correct answer: 4
The rate is proportional to [A]2, so it becomes 4 times.
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The unit of rate of reaction is:
- 1 s-1 only
- 2 mol dm-3
- 3 dm3 mol-1
- 4 mol dm-3 s-1
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Correct answer: mol dm-3 s-1
Rate = change in concentration per unit time.
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The half life of a first order reaction is:
- 1 Independent of initial concentration
- 2 Proportional to concentration
- 3 Inversely proportional to k only
- 4 Zero
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Correct answer: Independent of initial concentration
For first order, t1/2 = 0.693 / k, which does not depend on concentration.