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Chemical Kinetics

Short Answer Type

161. 75% of a reaction of the first order was completed in 32 minutes. When was its half-life completed?

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162. For the reaction A + B → 2C at a given temperature, the rate of disappearance of A is found to be 10^-² moles L^–1 sec^–1. Calculate (i) rate of disappearance of B and (ii) rate of formation of C.

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163. Calculate the half-life of the following first order reaction
C₂H₄ O₂(g) → CH₄(g) + CO₂(g)
Given the initial partial pressure of C₂H₄O₂(g) is 84 mm and the total pressure at the end of 16 min is 110 mm.

For the first order reaction for the gases phase given by

$k = \frac{2.303}{t} \log \frac{p_{1}}{p_{2}} where p_{1} = intial pressure p_{2} = final pressure$

we have give p₁ = 84mm
total pressure =110mm
at the time = 16 min

thus applying in above formula

$k = \frac{2.303}{16} \log \frac{84}{110} k = 0.1439 \log 0.7636 k = 0.1439 x 0.1171 k = 0.01685 also half life for the first order is given by t_{1 / 2} = \frac{0.693}{k} t_{1 / 2} = \frac{0.693}{0.01685} = 43.31 \min$

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Long Answer Type

164. For the first order reaction R → P, deduce the integrated form of the rate law. What will be the nature of the curve when concentration is plotted against time for such a reaction?

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165. State the role of activated complex in a reaction and state the relation with energy of activation.

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166. The rate law for the gas phase reaction of chlorform with chlorine.
CHCl₃(g) + Cl₂(g) → CCl ₄(g) + HCl(g)
is given by rate = k[CHCl₃] [Cl₂]^1/2. How would the rate of reaction vary when (a) the concentration of CHCl₃ is doubled (b) the concentration of Cl₂ is doubled. What is the effect of each of these two changes on the rate constant.

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