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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.

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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?

For the reaction

R → P

R a t e = - \frac{d [R]}{d t} = K [R] O r \frac{1}{[R]} d [R] = - k d t O n i n t e g r a t i n g b o t h s i d e s, w e g e t \int \frac{1 d [R]}{R} = - k \int d t I n [R] = - k t + I . . . . . (1) W h e r e I = i n t e g r a t i o n c o n s \tan t A t t = 0, [R] = [R]_{0} i n t i a l c o n c o f t h e r e a c \tan t p u r t t i n g t h i s i n e q (1) g i v e s I n [R]_{0} = - k x o + I a n d I = I n [R]_{0} s u b s t i t u t i n g t h e v a l u e o f I i n e q (1) g i v e s I n [R] = - K t + I n [R]_{0} C h a n g i n g i n t o \log 10 w e h a v e \log [R] = - \frac{k}{2.303} t + \log [R]_{0} W h e n \log [R] i s p l o t t e d a g a i n s t t i t g i v e s a s t r a i g h t l i n e w i t h s l o p e = \frac{- k}{2.303} a n d y i n t e r c e p t = \log [R]_{0} k = \frac{2.303}{t} \log \frac{[R]}{[R]_{0}}

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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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