Question

For a reaction $A+B\to$ Products, it is observed the doubling the concentration of $B$ causes the reaction rat to increase four times, but doubling the concentration of $A$ has no effect on the rate of reaction. The rate equation is therefore

• A. rate $=k[A{]}^2$
• B. rate $=k[B{]}^2$
• C. rate $=k[A][B]$
• D. rate $=k[A]$

Answer 1

Answer: (B)

$A+B\to$ Products

Let $R_1=k[A{]}^x[B{]}^y\dots (i)$

When $B^{\prime }=2B,R_2=4R_1$

Rate, $4R_1=k[A{]}^x[2B{]}^y\dots (ii)$

From equation (i) and (ii)

$4=\frac{[A{]}^x[2B{]}^y}{[A{]}^x[B{]}^y}$

$\Rightarrow 4=[2{]}^y$

$\Rightarrow y=2$

As concentration of $A$ have not effect, thus $x=0$

Rate $=k[A{]}^0[B{]}^2=k[B{]}^2$