A reaction, $A+B→C+D+q$ is found to have a positive entropy change. The reaction will be

Question

Consider the following changes : $\text{SnO}_2 \rightarrow \text{SnO}$ $\Delta G_1^o$ and $\text{PbO}_2 \rightarrow \text{PbO}$ $\Delta G_2^o$. Select the correct option

Answer 1

To determine the conditions under which the given reaction $A + B \rightarrow C + D + q$ with a positive entropy change is possible, we should consider the relationship between Gibbs free energy, entropy, and temperature:

The Gibbs free energy change, $\Delta G$, for a reaction is given by:

\[\Delta G = \Delta H - T\Delta S\]

Where:

$\Delta G$ is the change in Gibbs free energy.
$\Delta H$ is the change in enthalpy.
$T$ is the temperature in Kelvin.
$\Delta S$ is the change in entropy.

A reaction is spontaneous (or possible) when $\Delta G$ is negative.

In this problem, it is given that the entropy change $\Delta S$ is positive. Therefore, the term -T\Delta S becomes negative, which favors a negative $\Delta G$. Thus, this increases the likelihood of the reaction being spontaneous at any temperature.

Since the given reaction also releases heat $(+q)$, indicating an exothermic reaction, the enthalpy change $\Delta H$ is negative.

Therefore, for a reaction where both enthalpy change $\Delta H$ is negative and entropy change $\Delta S$ is positive, the reaction is spontaneous at any temperature.

Hence, the correct answer is: possible at any temperature.

Answer 2

To determine the conditions under which the given reaction $A + B \rightarrow C + D + q$ with a positive entropy change is possible, we should consider the relationship between Gibbs free energy, entropy, and temperature:

The Gibbs free energy change, $\Delta G$, for a reaction is given by:

\[\Delta G = \Delta H - T\Delta S\]

Where:

$\Delta G$ is the change in Gibbs free energy.
$\Delta H$ is the change in enthalpy.
$T$ is the temperature in Kelvin.
$\Delta S$ is the change in entropy.

A reaction is spontaneous (or possible) when $\Delta G$ is negative.

In this problem, it is given that the entropy change $\Delta S$ is positive. Therefore, the term -T\Delta S becomes negative, which favors a negative $\Delta G$. Thus, this increases the likelihood of the reaction being spontaneous at any temperature.

Since the given reaction also releases heat $(+q)$, indicating an exothermic reaction, the enthalpy change $\Delta H$ is negative.

Therefore, for a reaction where both enthalpy change $\Delta H$ is negative and entropy change $\Delta S$ is positive, the reaction is spontaneous at any temperature.

Hence, the correct answer is: possible at any temperature.

A reaction, \(A+B→C+D+q\) is found to have a positive entropy change. The reaction will be

The Correct Option is D

Solution and Explanation

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