Time required for completion of 99.9% of a First order reaction is ________ times of half life (t1/2) of the reaction.

The time required for completion of 99.9% of a first order reaction is 10 times the half-life (t1/2) of the reaction.

Here's the step by step explanation:

1. For a first order reaction, the time required to complete a certain percentage of reaction is given by the formula t = (ln(100/percentage remaining))/k, where k is the rate constant.

2. The half-life (t1/2) of a first order reaction is given by the formula t1/2 = 0.693/k.

3. To find the time required for 99.9% completion, we substitute 0.1 (which is 100 - 99.9) into the first formula to get t = ln(1000)/k.

4. Dividing this by the formula for half-life, we get (ln(1000)/k) / (0.693/k) = ln(1000)/0.693 = 10.

So, the time required for 99.9% completion of a first order reaction is 10 times the half-life of the reaction.