75% of a reaction of first order was completed in 64 minutes. When was its half completed?

If 99% of a first order reaction was completed in 32 minutes when will 99.9% of the reaction complete

80% of a first order reaction was completed in 70 min. How much it will take for 90% completion of a reaction?

Consider the following first order competing reactions: X overset(k_(1)) to A + B and Y overset(k_(2)) to C + D If 50% of the reaction of X was completed when 96% of the reaction of Y was completed, the ratio of thoir rate constant ( k_2 // k_1 ) is:

A first order reaction is 75 % complete in 60 minutes: Find the hatf-life of this.reaction.

The half life period of a reaction of first order is 100 sec. Calculate its rate constant.