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Class 12 Chemical Kinetics worksheet
CBSE Chemistry. Rate laws, order, zero- and first-order reactions, half-life, Arrhenius equation. Every sheet has 20 questions in three sections and an answer key, and the numbers change every time.
Sample questions
Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.
Section A · multiple choice
- 1.
The rate of a zero-order reaction:
- is proportional to the square of concentration
- is always zero
- is proportional to concentration
- does not depend on the concentration of the reactant
Answer
(d) does not depend on the concentration of the reactant
- 2.
For rate = k[A][B]², the overall order of the reaction is:
- 3
- 1
- 2
- 4
Answer
(a) 3
add the powers
- 3.
The unit of the rate constant of a third-order reaction, with time in seconds, is:
- s⁻¹
- mol L⁻¹ s⁻¹
- L mol⁻¹ s⁻¹
- L² mol⁻² s⁻¹
Answer
(d) L² mol⁻² s⁻¹
(mol L⁻¹)^(1 − n) s⁻¹ with n = 3
Section B · short answer
- 4.
Distinguish between order and molecularity of a reaction.
Answer
Order is the sum of the powers of concentrations in the experimental rate law; it can be zero or a fraction. Molecularity is the number of species colliding in an elementary step; it is a whole number (1, 2 or 3).
- 5.
For N₂ + 3H₂ → 2NH₃, H₂ is used up at 0.024 mol L⁻¹ s⁻¹. Find the rate of formation of NH₃ and the rate of the reaction.
Answer
0.016 mol L⁻¹ s⁻¹; rate of reaction 0.008 mol L⁻¹ s⁻¹
rate = −(1/3) d[H₂]/dt = (1/2) d[NH₃]/dt
Section C · long answer
- 6.
Derive the integrated rate equation for a first-order reaction and show that its half-life does not depend on the initial concentration.
Answer
−d[R]/dt = k[R] ⇒ d[R]/[R] = −k dt ⇒ ln[R] = −kt + ln[R]₀ ⇒ k = (2.303/t) log([R]₀/[R]). At t½, [R] = [R]₀/2, so k = (2.303/t½) log 2 ⇒ t½ = 0.693/k, which contains no concentration term.
Fresh sheets for your child
In the app, every Chemical Kinetics sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.
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