Question

The following are the data for the reaction

$A+B\to$ products

[A] [B] Initial rate $\left(mol{L}^{-1}{s}^{-1}\right)$

(i) 0.1 M 0.1 M $4.0\times {10}^{-4}$

(ii) 0.2 M 0.2 M $1.6\times {10}^{-3}$

(iii) 0.5 M 0.1 M $1.0\times {10}^{-2}$

(iv) 0.5 M 0.5 M $1.0\times {10}^{-2}$

The reaction rate when the concentration of A and B are 0.4 M and 0.7 M respectively :

• A. $6.4\times {10}^{-2}$
• B. $6.4\times {10}^{-3}$
• C. $6.4\times {10}^{-4}$
• D. $6.4\times {10}^{-5}$

Answer 1

Answer: (B)

$6.4\times {10}^{-3}$

On increasing the concentration of B five times keeping the concentration of A constant, the rate doesn't change therefore the order w.r.t B is zero.

On increasing the concentration of A five times, the rate increases 25 times therefore, the order w.r.t A is two.

Rate $=k\left[A{|}^2\right[B{]}^0$

$=(4.0\times {10}^{-2})\left(0.4{)}^2\right(0.7{)}^0$

$=4.0\times {10}^{-2}\times 0.4\times 0.4\times 1$

$=6.4\times {10}^{-3}$