Question

A zero order reaction is $50\text{\%}$ complete in $20\text{min.}$ How much time will it take to complete $90\text{\%}$?

• A. $36\text{min}$
• B. $46\text{min}$
• C. $26\text{min}$
• D. $30\text{min}$

Answer 1

The correct option is A $36\text{min}$

Let, $a=100{\text{mol dm}}^{-3}$. For a zero-order reaction
$k=\frac{x}{t}=\frac{50{\text{(mol dm}}^{-3})}{20\times 60\text{(sec)}}$
when reaction is $90\text{\%}$ complete, $x=90$. Therefore,
Thus, $\frac{50}{1200}=\frac{90}{t}$
or $t=\frac{90\times 1200}{50}=2160\text{sec}=36\text{min}$