(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.