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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.

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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.

Given that initial temperature, T₁ = 298 K
Final temperature, T₂ = 298 + 10 = 308 K
Rate of chemical reaction will increase with raise of rate constant so that take
Initial value of rate constant k₁ = k
find rate constant, k₂ = 2k
Also, R = 8.314 J K⁻¹ mol⁻¹
Use Arrhenius equation

According to Arrchenium equation,

\log \frac{k_{2}}{k_{1}} = \frac{Ea}{2.303 R} [\frac{1}{T_{1}} - \frac{1}{T_{2}}]

\frac{k_{2}}{k_{1}} = 2, T_{1} = 298 K, T_{2} = 298 + 10 = 308 k R = 8.314 J k^{- 1} {mol}^{- 1}

\log 2 = \frac{Ea}{2.303 \times (8.314 J K^{- 1} {mol}^{- 1})} [\frac{1}{298 k} - \frac{1}{308 k}]

0.3010 = \frac{Ea}{2.303 \times 8.314} \times \frac{10}{298 \times 308}

Ea = \frac{0.3010 \times 2.303 \times 8.314 \times 298 \times 308}{10} J {mol}^{- 1}

Ea = \frac{0.3010 \times 2.303 \times 8.314 \times 298 \times 308}{10 \times 100} kJ {mol}^{- 1} = 52.89 kJ {mol}^{- 1}

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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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