Question

The rate of reaction between two reactants A and B decreases by a factor of 4 if the concentration of reactant B is doubled. The order of this reaction with respect to reactant B is

• A. 2
• B. -2
• C. 1
• D. -1

Answer 1

The correct option is B -2

Let order w.r.t. to B is n.

Then, $r\propto [B{]}^n$

$\frac{1}{4}r\propto [B{]}^n$

Divide $\frac{\frac{1}{4}r}{r}\propto {\left[\frac{2B}{B}\right]}^n$

or, $\frac{1}{4}=2^n$

or, ${\left(\frac{1}{2}\right)}^2=2n$ or, $2^{-2}=2^n$

$\therefore n=-2$