Which of the following expressions represents the criterion for the reaction to be spontaneous?

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This question was previously asked in

DSSSB PGT Chemistry (Female) Official Paper (Held On: 06 Jul, 2018 Shift 1)

Answer 1

CONCEPT:

Spontaneity of a Reaction

The spontaneity of a reaction is determined by the change in Gibbs free energy (G).
For a reaction to be spontaneous, the Gibbs free energy must decrease (dG < 0) under constant temperature (T) and pressure (P).
The condition dG < 0 indicates that the system's free energy decreases during the reaction, favoring the process naturally without requiring external work.

EXPLANATION:

(dS)u,v < 0 — This condition relates to entropy change at constant internal energy (u) and volume (v), but it does not represent spontaneity directly.
(dU)S,V > 0 — This condition relates to internal energy change at constant entropy (S) and volume (V), but it does not define spontaneity.
(dG)T,P < 0 — This is the correct criterion for spontaneity as it directly relates to the decrease in Gibbs free energy under constant temperature (T) and pressure (P).
(dH)T,P > 0 — This condition relates to enthalpy change under constant temperature (T) and pressure (P), but it does not define spontaneity.
Thus, the correct criterion for a reaction to be spontaneous is (dG)T,P < 0.

Therefore, the correct answer is Option 3.

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