1. First order reaction.
2. 1/4th life of a first order reaction can be determined as follows.
\(k=\frac{2.303}{t}log\frac{[R]_0}{[R]}\)
When t = t/4, [R] can be taken as \(\frac{[R]_0}{4}\)
\(k=\frac{2.303}{t/4}log\,4\,;\)
\(k=\frac{2.303}{t/4}\times log\,4\)
tt/4 = \(\frac{2.303\,\times\,log\,4}{k}\)
\(=\frac{2.303\,\times\,0.6020}{k}\)
\(=\frac{1.386}{k}\)