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Chemical Kinetics

Long Answer Type

261. The pressure of a gas decomposing at the surface of a solid catalyst has been measured at different times and the results are given below:

t/s	0	100	200	300
p/p_a	4.00 x 10³	3.50 x 10³	3.00 x 10³	2.5 x10³

Determine the order of reaction, its rate constant and half-life period?
It can be seen that rate of reaction between different time interval is

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Short Answer Type

262. Calculate the half-life period of a first order reaction when the rate constant is 5 year^–1.

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Long Answer Type

263. Show that in first order reaction time required for completion of 99.9% is 10 times of half-life (t_1/2) of the reaction.

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264. If half life of a first order reaction involving reactant A is 5 min. How long will it take [A] to reach 25% of its initial concentration?

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Short Answer Type

265. The activation energy of a reaction is 94.14 kJ mol^–1 and the value of rate constant at 313 K is 1.8 x 10^–5 sec^–1. Calculate the frequency factor A.

We have given

E_{a} = 94.14 kJ {mol}^{- 1} = 94140 J {mol}^{- 1} T = 313, k = 1.8 \times 10^{- 5} \sec^{- 1}

thus by usingv Arrhenius equation,

Now,

\log k = \frac{- E_{a}}{2.303 RT} + \log A

We get,

logA = \log (1.8 \times 10^{- 5}) + \frac{94140}{2.303 \times 8.314 \times 313} = (\log 1.8) - 5 + 15.7082 = 0.2553 - 5 + 15.7082 = 10.9635

Therefore,

A = anti \log (10.9635) = 9.194 \times 10^{10} collisions / \sec .

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266. The rate of a particular reaction doubles when temperature changes from 27°C to 37°C. Calculate the energy of activation of such a reaction.

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Long Answer Type

267. The rate constant of a reaction is 1.2 x 10^–3 sec^–3 at 30°C and 2.1 x 10^–3 sec^–1 at 40°C. Calculate the energy of activation of the reaction.

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Short Answer Type

268. The rate constant of reaction is 1.5 x 10⁷ sec^–1 at 50°C and 4.5 x10⁷ sec^–1 at 100°C. Calculate the value of activation energy, E_a for the reaction (R =8.314 JK^–1 mol^–1).

799 Views

Long Answer Type

269. In the Arrhenius equation for certain reaction, the values of the frequency factor and energy of activation are 4 x 10¹³ sec^–1 and 98.6 kJ/mol respectively. If the reaction is of first order, at what temperature will its half-life be 10 minutes.

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