Question

Consider the chemical reaction,

2A (g) $\longrightarrow$B(g) + 3C(g)

The rate of this reaction can be expressed in terms of time derivatives of conc. of A(g) , B(g) or C(g). Identify the correct relationship amongst rate expressions :

• A. Rate = – $\frac{d\lbrack A\rbrack}{dt} = \frac{d\lbrack B\rbrack}{dt} = \frac{d\lbrack C\rbrack}{dt}$
• B. Rate =$\frac{1}{2}\frac{d\lbrack A\rbrack}{dt} = \frac{d\lbrack B\rbrack}{dt} = \frac{1}{3}\frac{d\lbrack C\rbrack}{dt}$
• C. Rate = –$\frac{1}{2}\frac{d\lbrack A\rbrack}{dt} = \frac{d\lbrack B\rbrack}{dt} = \frac{1}{3}\frac{d\lbrack C\rbrack}{dt}$
• D. Rate = $\frac{1}{2}\frac{d\lbrack A\rbrack}{dt} = - \frac{d\lbrack B\rbrack}{dt} = - \frac{1}{3}\frac{d\lbrack C\rbrack}{dt}$

Answer 1

Answer: (C)

Rate = –$\frac{1}{2}\frac{d\lbrack A\rbrack}{dt} = \frac{d\lbrack B\rbrack}{dt} = \frac{1}{3}\frac{d\lbrack C\rbrack}{dt}$

Answer 2

2A [g] $\longrightarrow$ B[g] + 3C[g] [elementary reaction]

Rate = – $\frac{1}{2}\frac{d\lbrack A\rbrack}{dt} = \frac{d\lbrack B\rbrack}{dt} = \frac{1}{3}\frac{d\lbrack C\rbrack}{dt}$