The rate of the reaction [tex]\( NO_2 (g) + CO (g) \rightarrow NO (g) + CO_2 (g) \)[/tex] was determined in three experiments at [tex]\( 225^{\circ} \text{C} \)[/tex].

The results are given in the following table:

| Experiment | [tex]\([NO_2]_0\)[/tex] (M) | [tex]\([CO]_0\)[/tex] (M) | Initial Rate [tex]\(-\Delta [NO_2]/\Delta t\)[/tex] [tex]\((M/s)\)[/tex] |
|------------|-------------------|----------------|--------------------------------------------|
| 1 | 0.263 | 0.826 | [tex]\( 1.44 \times 10^{-5} \)[/tex] |
| 2 | 0.263 | 0.413 | [tex]\( 1.44 \times 10^{-5} \)[/tex] |
| 3 | 0.526 | 0.413 | [tex]\( 5.76 \times 10^{-5} \)[/tex] |

Calculate the rate of appearance of [tex]\( CO_2 \)[/tex] when [tex]\( [NO_2] = [CO] = 0.495 \, M \)[/tex].

[tex]\[ \text{Rate of appearance of } CO_2 = \quad \text{M/s} \][/tex]



Answer :

Sure! Let’s solve this step-by-step to find the rate of appearance of [tex]\( \text{CO}_2 \)[/tex] given the concentrations [tex]\([ \text{NO}_2 ] = [ \text{CO} ] = 0.495 \, \text{M}\)[/tex].

### Step 1: Determine the Reaction Orders

Given the rate law in the form:
[tex]\[ \text{rate} = k [\text{NO}_2]^x [\text{CO}]^y \][/tex]

We have the experimental data from 3 experiments:

1. Experiment 1:
- [tex]\([ \text{NO}_2 ]_1 = 0.263 \, \text{M}\)[/tex]
- [tex]\([ \text{CO} ]_1 = 0.826 \, \text{M}\)[/tex]
- [tex]\(\text{rate}_1 = 1.44 \times 10^{-5} \, \text{M/s}\)[/tex]

2. Experiment 2:
- [tex]\([ \text{NO}_2 ]_2 = 0.263 \, \text{M}\)[/tex]
- [tex]\([ \text{CO} ]_2 = 0.413 \, \text{M}\)[/tex]
- [tex]\(\text{rate}_2 = 1.44 \times 10^{-5} \, \text{M/s}\)[/tex]

3. Experiment 3:
- [tex]\([ \text{NO}_2 ]_3 = 0.526 \, \text{M}\)[/tex]
- [tex]\([ \text{CO} ]_3 = 0.413 \, \text{M}\)[/tex]
- [tex]\(\text{rate}_3 = 5.76 \times 10^{-5} \, \text{M/s}\)[/tex]

#### Finding the order with respect to [tex]\( \text{CO} \)[/tex] [tex]\((y)\)[/tex]:

Comparing Experiment 1 and Experiment 2 where [tex]\([ \text{NO}_2 ]\)[/tex] is constant:
[tex]\[ \frac{\text{rate}_2}{\text{rate}_1} = \left( \frac{[\text{CO}]_2}{[\text{CO}]_1} \right)^y \][/tex]

[tex]\[ \frac{1.44 \times 10^{-5}}{1.44 \times 10^{-5}} = \left( \frac{0.413}{0.826} \right)^y \][/tex]

[tex]\[ 1 = \left( 0.5 \right)^y \][/tex]

Here, [tex]\( y \)[/tex] would be 0 (since the ratio results in 1, indicating a zero-order dependence on [tex]\( [\text{CO}] \)[/tex]).

#### Finding the order with respect to [tex]\( \text{NO}_2 \)[/tex] [tex]\((x)\)[/tex]:

Comparing Experiment 1 and Experiment 3 where [tex]\([ \text{CO} ]\)[/tex] is constant:
[tex]\[ \frac{\text{rate}_3}{\text{rate}_1} = \left( \frac{[\text{NO}_2]_3}{[\text{NO}_2]_1} \right)^x \][/tex]

[tex]\[ \frac{5.76 \times 10^{-5}}{1.44 \times 10^{-5}} = \left( \frac{0.526}{0.263} \right)^x \][/tex]

[tex]\[ 4 = (2)^x \][/tex]

Here, [tex]\( x \)[/tex] would be close to 3.71 (since [tex]\( 2^{3.71} \approx 4 \)[/tex]).

### Step 2: Determine the Rate Constant [tex]\( k \)[/tex]

Using the data from Experiment 1 and the determined reaction orders:

[tex]\[ \text{rate}_1 = k [\text{NO}_2]_1^x [\text{CO}]_1^y \][/tex]
[tex]\[ 1.44 \times 10^{-5} = k (0.263)^{3.71} (0.826)^0 \][/tex]

[tex]\[ k = \frac{1.44 \times 10^{-5}}{(0.263)^{3.71}} k \approx 0.000625 \, \text{M}^{1-3.71} \text{s}^{-1} \][/tex]

### Step 3: Calculate the Rate of Appearance of [tex]\( \text{CO}_2 \)[/tex]

Given new concentrations [tex]\([ \text{NO}_2 ] = [ \text{CO} ] = 0.495 \, \text{M}\)[/tex], the rate of appearance of [tex]\( \text{CO}_2 \)[/tex] is:
[tex]\[ \text{rate}_{\text{new}} = k [\text{NO}_2]^{x} [\text{CO}]^{y} \][/tex]
[tex]\[ \text{rate}_{\text{new}} = 0.000625 \times (0.495)^{3.71} \times (0.495)^0 \][/tex]
[tex]\[ \text{rate}_{\text{new}} = 0.000625 \times (0.495)^{3.71} \][/tex]
[tex]\[ \text{rate}_{\text{new}} \approx 4.60 \times 10^{-5} \, \text{M/s} \][/tex]

Therefore, the rate of appearance of [tex]\( \text{CO}_2 \)[/tex] when [tex]\([ \text{NO}_2 ] = 0.495 \, \text{M}\)[/tex] and [tex]\([ \text{CO} ] = 0.495 \, \text{M}\)[/tex] is approximately [tex]\( 4.60 \times 10^{-5} \, \text{M/s} \)[/tex].