\(A \rightarrow B\) (first reaction)
\(C \rightarrow D\) (second reaction)
Consider the above two first-order reactions. The rate constant for first reaction at 500 K is double of the same at 300 K . At \(500 K, 50 \%\) of the reaction becomes complete in 2 hour. The activation energy of the second reaction is half of that of first reaction. If the rate constant at 500 K of the second reaction becomes double of the rate constant of first reaction at the same temperature; then rate constant for the second reaction at 300 K is __________ \(\times 10^{-1}\) hour \(^{-1}\) (nearest integer).

1. A 4.5
2. B 4.9
3. C 5
4. D 5.5