Question

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

Answer 1

Answer: Time required to complete 99.9 % reaction is 48.16 mins.

Solution :

For first order reactions, rate is written as:

$k=\frac{2.303}{t}log\left(\frac{a}{a-x}\right)$

where, k = rate constant

t = time

a = product formed

a - x = reactant left in the reaction

When the reaction is 99 % completed

a = 100

a - x = 100 - 99 = 1

Putting the values in rate equation, we get

$k=\frac{2.303}{32\times 60}log\left(\frac{100}{1}\right)$

$k=2.39\times 10^{-3}sec^{-1}$

As the rate constant for the reaction remains same. Now, when the reaction is 99.9% completed

a = 100

a - x = 100 - 99.9 = 0.1

Putting the values in the above rate equation, we get

$2.39\times 10^{-3}=\frac{2.303}{t}log\left(\frac{100}{0.1}\right)$

t = 2890 second

t = 48.16 min          (1 min = 60 sec)

Therefore, time required to complete 99.9 % reaction is 48.16 mins.

Answer 2

Answer:

answer is 48. follow the first order reaction equation.