The gas-phase reaction [tex]$2 NO + 2 H_2 \rightarrow N_2 + 2 H_2O$[/tex] has the following rate law expression:

[tex]\[
\text{rate} = 0.14 \frac{L^2}{mol^2 \cdot s} [NO]^2[H_2]
\][/tex]

If the [tex]$[NO]$[/tex] is 0.95 M and the [tex]$[H_2]$[/tex] is 0.45 M, what rate is expected?

A. [tex]$0.060 \frac{mol}{L \cdot s}$[/tex]

B. [tex]$0.43 \frac{mol}{L \cdot s}$[/tex]

C. [tex]$0.027 \frac{mol}{L \cdot s}$[/tex]

D. [tex]$1.54 \frac{mol}{L \cdot s}$[/tex]

E. [tex]$0.057 \frac{mol}{L \cdot s}$[/tex]



Answer :

To determine the rate of the given gas-phase reaction, we should follow a step-by-step approach using the provided rate law expression and given concentrations.

1. Identify the Rate Law Expression:
The rate law for the reaction [tex]\(2 NO + 2 H_2 \rightarrow N_2 + 2 H_2O\)[/tex] is given by:
[tex]\[ \text{rate} = 0.14 \, \text{L}^2 / (\text{mol}^2 \cdot \text{s}) \cdot [NO]^2 \cdot [H_2] \][/tex]

2. Substitute the Given Concentrations:
The concentrations of the reactants are provided:
[tex]\[ [NO] = 0.95 \, \text{M} \][/tex]
[tex]\[ [H_2] = 0.45 \, \text{M} \][/tex]

3. Calculate the Rate:
Substitute the given concentrations into the rate law expression:
[tex]\[ \text{rate} = 0.14 \, \text{L}^2 / (\text{mol}^2 \cdot \text{s}) \cdot (0.95 \, \text{M})^2 \cdot (0.45 \, \text{M}) \][/tex]

4. Calculate [tex]\((0.95 \, \text{M})^2\)[/tex]:
[tex]\[ (0.95 \, \text{M})^2 = 0.9025 \, \text{M}^2 \][/tex]

5. Multiply by [tex]\(0.45 \, \text{M}\)[/tex]:
[tex]\[ 0.9025 \, \text{M}^2 \times 0.45 \, \text{M} = 0.406125 \, \text{M}^3 \][/tex]

6. Multiply by the Rate Constant [tex]\(0.14 \, \text{L}^2 / (\text{mol}^2 \cdot \text{s})\)[/tex]:
[tex]\[ 0.14 \, \text{L}^2 / (\text{mol}^2 \cdot \text{s}) \times 0.406125 \, \text{M}^3 = 0.0568575 \, \text{mol} / (\text{L} \cdot \text{s}) \][/tex]

Thus, the calculated rate of the reaction is approximately:
[tex]\[ 0.057 \, \text{mol} / (\text{L} \cdot \text{s}) \][/tex]

From the given options, the expected rate is:
[tex]\[ 0.057 \, \text{mol} / (\text{L} \cdot \text{s}) \][/tex]

Hence, the correct answer is:
[tex]\[ \boxed{0.057 \, \text{mol} / (\text{L} \cdot \text{s})} \][/tex]