Question

The reaction: $2NO + 2H_{2}\overset{\quad\quad}{\rightarrow}N_{2} + 2H_{2}O$ has been assigned to follow following mechanism.

}{II.N_{2}O_{2} + H_{2}\overset{\quad\quad}{\rightarrow}N_{2} + H_{2}O(slow) }{III.N_{2}O + H_{2}\overset{\quad\quad}{\rightarrow}N_{2} + H_{2}O(fast)}$$ The rate constant of step II is 1.2 x 10-4mol-1L.min-1 while equilibrium constant of step I is 1.4 x 10-2 .What is the rate of reaction when concentration of NO and H2 each is 0.5 mole L-1

• A. 2.1 x 10-7 mole L-1 min-1
• B. 3.2 x 10-6 mole L-1 min-1
• C. 3.5 x 10-4 mole L-1 min-1
• D. None of these

Answer 1

Answer: (A)

2.1 x 10-7 mole L-1 min-1

Answer 2

$K_{\text{obs}}\text{ = k. }\text{K}_{c}\text{ = 1. 2 x 1}\text{0}^{\text{-1}}\text{ x 1. 4 }

}{\text{Rate = }\text{K}_{\text{obs}}\lbrack\text{ NO}\rbrack_{2}\ \lbrack\text{ }\text{H}_{2}\rbrack\ }{\text{= 1.68 x 1}\text{0}^{\text{-6}}\text{ x 0.}\text{5}^{2}\text{ x 0.5 } }{\text{= 2.1 x 1}\text{0}^{\text{-7}}\text{ mole L}\text{ }^{\text{-1}}\text{ mi}\text{n}^{\text{-1}}}$$