Following lists contain reactions and their corresponding equilibrium constants at different temperatures: List - I (Reaction) List - II Kp 2SO2( g)+O2( g)⇌2SO3( g) at 298 K 4.0×1024 2SO2( g)+O2( g)⇌2SO3( g) at 700 K 3.0×104 N2O4( g)⇌2NO2( g) at 298 K 0.98 N2O4( g)⇌2NO2( g) at 500 K 1700 If ∆H10 and ∆H20 are the standard enthalpies for the reactions 2SO2 + O2 ⇌ 2SO3 and N2O4 ⇌ 2NO2 respectively, then:

(A) Both ∆H10 and ∆H20 are negative

(B) Both ∆H10 and ∆H20 are positive

(D) ∆H10 is positive and ∆H20 is negative

TS EAMCET · Chemistry · Thermodynamics (C)

Following lists contain reactions and their corresponding equilibrium constants at different temperatures:

List - I (Reaction) List - II $(K_{p})$

$2 {SO}_{2} (g) + O_{2} (g) ⇌ 2 {SO}_{3} (g) at 298 K$ $4.0 \times 10^{24}$

$2 {SO}_{2} (g) + O_{2} (g) ⇌ 2 {SO}_{3} (g) at 700 K$ $3.0 \times 10^{4}$

$N_{2} O_{4} (g) ⇌ 2 {NO}_{2} (g) at 298 K$ $0.98$

$N_{2} O_{4} (g) ⇌ 2 {NO}_{2} (g) at 500 K$ $1700$

If $∆ H_{1}^{0} and ∆ H_{2}^{0}$ are the standard enthalpies for the reactions $2 {SO}_{2} + O_{2} ⇌ 2 {SO}_{3} and N_{2} O_{4} ⇌ 2 {NO}_{2}$ respectively, then:

A $Both ∆ H_{1}^{0} and ∆ H_{2}^{0} are negative$
B $Both ∆ H_{1}^{0} and ∆ H_{2}^{0} are positive$
C $∆ H_{1}^{0} is negative and ∆ H_{2}^{0} is positive$
D $∆ H_{1}^{0} is positive and ∆ H_{2}^{0} is negative$

Verified Solution

Answer & Solution

Correct Answer

(C) $∆ H_{1}^{0} is negative and ∆ H_{2}^{0} is positive$

Step-by-step Solution

Detailed explanation

From thermodynamics of equilibria, we have: ln Kep = ln A - ∆H0RT For endothermic reaction, the equilibrium constant increases with temperature while for the exothermic reaction, the equilibrium constant decreases when temperature is raised.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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List - I (Reaction)	List - II $(K_{p})$
$2 {SO}_{2} (g) + O_{2} (g) ⇌ 2 {SO}_{3} (g) at 298 K$	$4.0 \times 10^{24}$
$2 {SO}_{2} (g) + O_{2} (g) ⇌ 2 {SO}_{3} (g) at 700 K$	$3.0 \times 10^{4}$
$N_{2} O_{4} (g) ⇌ 2 {NO}_{2} (g) at 298 K$	$0.98$
$N_{2} O_{4} (g) ⇌ 2 {NO}_{2} (g) at 500 K$	$1700$