Question

For the reaction,
$H _{2}(g)+ Br _{2}(g) \longrightarrow 2 HBr (g)$ the reaction rate is given by $r=k\left[ H _{2}\right]\left[ Br _{2}\right]^{1 / 2}$.
Which of the following statements are true?
I. Molecularity of reaction is $1.5$.
II. Order of reaction is $2$ .
III. Molecularity of reaction is $2$ .
IV. Order of reaction is $1.5$.
Choose the correct option.

• A. $I$ and $III$
• B. $I$ and $II$
• C. $II$ and $III$
• D. $III$ and $IV$

Answer 1

Answer: (D)

$H _{2}(g)+ Br _{2}(g) \longrightarrow 2 HBr (g)$
rate $=k\left[ H _{2}\right]\left[ Br _{2}\right]^{1 / 2},$ molecularity $=2$
Order $=1+\frac{1}{2}=\frac{3}{2}$