Instantaneous rate of a reaction is $$ - {1 \over 2}{{d[x]} \over {dt}} = - {{d[y]} \over {dt}} = {1 \over 2}{{d[z]} \over {dt}}$$, identify the reaction.

Half life for a first order reaction is 6.93 hour. What is the time required for 80% completion of the reaction?

For first order reaction the concentration of reactant decreases from 0.2 to 0.1 M in 100 minutes. What is the rate constant of the reaction?

A first order reaction is $25 \%$ completed in 40 minutes. What is the rate constant $k$ for the reaction?