# a). A first order reaction takes 40 minutes for 30 % decomposition. Calculate 1/2.

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a). A first order reaction takes 40 minutes for 30 % decomposition. Calculate 1/2

b). The following results have been obtained during the kinetics of the reaction:

2A + B → C + D

 Experiment No. [A] [B] Initial Rate of formation of D 1 0.1 M 0.1 M 6.0 × 10−3 M min−1 2 0.3 M 0.2 M 7.2× 10−2  M min−1 3 0.3 M 0.4 M 2.88 × 10−1 M min−1 4 0.4 M 0.1 M 2.4 × 10−2 M min −1

Determine the Rate law and the rate constant for the reaction:

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(a) k = $\frac{2.303}{t}$ log $\frac{[A]_o}{[A]}$

Substituting the values, we have

k = $\frac{2.303}{40}$ log $\frac{100}{70}$

or k = $\frac{2.303}{40}$ x 0.159 = 0.0089 min-1

t1/2 $\frac{0.693}{k}$ = $\frac{0.693}{0.0089}$ = 77.86 minutes

(b) Suppose order w.r.t A is a and w.r.t B is b Rate = k [A]a [B]b Rate law expression is: Rate = k[A][B]2.

k can be calculated as in the first method.

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