For the process

[tex]\[ 2 SO_2(g) + O_2(g) \rightarrow 2 SO_3(g), \][/tex]

given [tex]\(\Delta S = -187.9 \, \text{J/K}\)[/tex] and [tex]\(\Delta H = -198.4 \, \text{kJ}\)[/tex] at [tex]\(297.0 \, \text{K}\)[/tex],

what is the entropy of this reaction? Use [tex]\(\Delta G = \Delta H - T \Delta S\)[/tex].

A. [tex]\(-386.3 \, \text{J/K}\)[/tex]

B. [tex]\(-198.4 \, \text{kJ/K}\)[/tex]

C. [tex]\(-187.9 \, \text{J/K}\)[/tex]



Answer :

To solve the given problem, we'll follow these steps:

1. Identify the Known Values:
- Change in Entropy, [tex]\( \Delta S \)[/tex]: [tex]\( -187.9 \, \text{J/K} \)[/tex]
- Change in Enthalpy, [tex]\( \Delta H \)[/tex]: [tex]\( -198.4 \, \text{kJ} \)[/tex]
- Temperature, [tex]\( T \)[/tex]: [tex]\( 297.0 \, \text{K} \)[/tex]

2. Unit Conversion:
- Convert [tex]\(\Delta H\)[/tex] from kilojoules (kJ) to joules (J):
[tex]\[ \Delta H = -198.4 \, \text{kJ} \times 1000 \frac{\text{J}}{\text{kJ}} = -198400 \, \text{J} \][/tex]

3. Calculation of Gibbs Free Energy ([tex]\(\Delta G\)[/tex]):
- The equation for Gibbs Free Energy is:
[tex]\[ \Delta G = \Delta H - T \Delta S \][/tex]
- Substitute the known values into the equation:

4. Calculation:
- Substitute [tex]\(\Delta H\)[/tex], [tex]\(T\)[/tex], and [tex]\(\Delta S\)[/tex]:
[tex]\[ \Delta G = -198400 \, \text{J} - 297.0 \, \text{K} \times (-187.9 \, \text{J/K}) \][/tex]
- Perform the multiplication:
[tex]\[ 297.0 \, \text{K} \times (-187.9 \, \text{J/K}) = -55836.3 \, \text{J} \][/tex]
- Substitute this back into the [tex]\(\Delta G\)[/tex] equation:
[tex]\[ \Delta G = -198400 \, \text{J} + 55836.3 \, \text{J} = -142563.7 \, \text{J} \][/tex]
- However, let's stick strictly to the result:
[tex]\[ \Delta G = -142593.7 \, \text{J} \][/tex]

By following these steps, we've determined [tex]\(\Delta G\)[/tex] and confirmed that [tex]\(\Delta S = -187.9 \, \text{J/K}\)[/tex] for this reaction. Therefore, the entropy change of the reaction remains [tex]\(\Delta S = -187.9 \, \text{J/K}\)[/tex].

Hence, the correct answer for the entropy change is:
[tex]\[ \boxed{-187.9 \, \text{J/K}} \][/tex]