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Chemical Kinetics

Short Answer Type

1. For the reaction R → P, the concentration of a reactant changes from 0.03 M to 0.02 M is 25 minutes. Calculate the average rate of reaction using units of time both in minutes and seconds.

Given that
Initial concentration, [R1] = 0.03
Final concentration, [R2] = 0.02
Time taken ∆t = 25 min = 25 × 6 0 = 1500 sec (1 min = 60 sec )
The formula of average rate of change

r_{av} = \frac{- ∆ R}{∆ t} = \frac{∆ [P]}{∆ t}

(i) Average rate

= \frac{(0.03 - 0.02) M}{25 \times 60 \sec} = \frac{0.01 M}{25 \times 60 s} = 6.66 M s^{- 1}

(ii) Average rate

= \frac{(0.03 - 0.02) M}{25 \min} = \frac{0.01 M}{25} = 0.0004 {Ms}^{- 1} .

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2. In a reaction 2A → Products, the concentration of A decreases from 0.5 mol to 0.4 mol L^–1 in 10 minutes. Calculate the rate during this interval.

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3. For a reaction, A + B → Product; the rate law is given by, r = k[ A]^1/2 [B]². What is the order of reaction?

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4. The conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y?

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5. A first order reaction has a rate constant 1.15 x 10^–3 s^–1. How long will 5 g of this reactant take to reduce to 3 g?

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6. Time required to decompose SO₂ Cl₂ to half its initial amount is 60 minutes. If the decomposition is a first order reaction, calculate the rate constant of the reaction.

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7. What will be the effect of temperature on rate constant?

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Long Answer Type

8. The rate of the chemical reaction doubles for an increase of 10 k in absolute temperature from 298 K. Calculate E_a.

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Short Answer Type

The activation energy for the reaction
2HI (g) → H₂ + I₂(g)
is 209.5 kJ mol^–1 at 581 k. Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?

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10. For the reaction A B, the rate of reaction becomes twenty seven times when the concentration of A is increased three times.
What is the order of the reaction?

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