Question

For a reaction $2A + B \rightarrow$Products, doubling the initial concentration of both the reactants increases the rate by a factor of 8, and doubling the concentration of B alone doubles the rate. The rate law for the reaction is.

• A. $\gamma = k\lbrack A\rbrack\lbrack B\rbrack^{2}$
• B. $\gamma = k\lbrack A\rbrack^{2}\lbrack B\rbrack$
• C. $\gamma = k\lbrack A\rbrack\lbrack B\rbrack$
• D. $\gamma = k\lbrack A\rbrack^{2}\lbrack B\rbrack^{2}$

Answer 1

Answer: (B)

$\gamma = k\lbrack A\rbrack^{2}\lbrack B\rbrack$

Answer 2

$2A + B \rightarrow$Products

According to question : Rate of reaction of ‘A’$\propto$ [B] as increase in rate is double when [B] is doubled.

Rate of reaction $\propto$ [A] [B] as increase in rate is 8 times when concentration of both reactant is doubled. It means that order of reaction is 3 and overall rate reaction should be

$r = K\lbrack A\rbrack^{2}\lbrack B\rbrack$