Question

in a zero order reaction 20% of the reaction complete in 10s. how much time it will take to complete 50% of the reaction

Answer 1

Dear student,
For zero order reaction - x = kt
​Where, x = decrease in concentration of reactant (mol dm^-3) , k = rate constant (mol dm^-3 sec^-1) , t = time (sec)
Also, for 50% completion of reaction, i.e. Half life of reaction , $t_{\frac{1}{2}}=\frac{a}{2k}$; where a = initial concentration of reactant.
Let a = 100 mol dm^-3 and after 20% competion of reaction , x = 20 ​ mol dm^-3. Now,
$$\begin{gathered} k=\frac{20moldm-3}{10sec} \\ k=2mold{m}^{-3}se{c}^{-1} \end{gathered}$$
and $t_{1/2}=\frac{100mold{m}^{-3}}{2\times 2mold{m}^{-3}se{c}^{-1}}$
t_1/2 = 25 sec.

Regards