Question

For the zero order reaction A => B+C initial concentration of A is 0.1M. If {A}= 0.08M after 10minutes then it's half life and completion time are?

Answer 1

first of all we have to calculate the rate constant for given order of reaction then we have to find out the half life using the formula Given above

Answer 2

Answer : The half life and completion time are 25 min and 50 min respectively.

Explanation :

Zero order reaction : A reaction is said to be of zero order if the rate is independent of the concentration of the reactants, that means the rate is directly proportional to the zeroth power of the concentration of the reactants.

The zero order reaction  is,

$A\rightarrow B+C$

The expression for the rate constant of zero order will be,

$[A]_t=-kt+[A]_o$

or,

$k=\frac{1}{t}\times ([A]_o-[A]_t)$

where,

k = rate constant = ?

t = time

$[A]_o$ = initial concentration = 0.1 M

$[A]_t$ = concentration at time 10 min. = 0.08 M

Now put all the given values in above expression, we get :

$k=\frac{1}{10}\times (0.1-0.08)=0.002min^{-1}$

Now we have to calculate the half life.

Formula used : $t_{1/2}=\frac{[A]_o}{2k}$

Now put all the given values in this formula, we get :

$t_{1/2}=\frac{0.1}{2\times 0.002}=25min$

Now e have to calculate the completion time.

Formula used : $t_{comp}=2\times t_{1/2}$

Now put all the given values in this formula, we get :

$t_{comp}=2\times 25=50min$

Therefore, the half life and completion time are 25 min and 50 min respectively.