The correct statement amongst the following is :

Question

For reaction $A \rightleftharpoons B$, $\Delta G^{\circ} = 105 - 35 \log T$. Find the transition temperature (in $^{\circ} C$) of the above reaction at 1 bar.

Answer 1

The objective is to identify the correct statement concerning standard states and enthalpies of formation. Each option will be assessed according to established chemical principles:

The term 'standard state' implies a temperature of $0^\circ C$: ^{}\right\wing This is incorrect. The standard state is a reference condition for thermodynamic calculations, not defined by a specific temperature. While 25°C (298 K) is frequently used, it is not the definition of the standard state.
The standard state of a pure gas is the pure gas at 1 bar pressure and 273 K: This statement is partially incorrect. The standard state for a gas is defined as the pure gas at 1 bar pressure. However, a fixed temperature like 273 K is not mandated; standard enthalpies are typically recorded at 298 K, not 273 K.
$\Delta_f H_{298}^\ominus$ is zero for O(g): This is incorrect. $\Delta_f H_{298}^\ominus$ represents the standard enthalpy of formation. For diatomic oxygen ($O_2(g)$), the standard enthalpy of formation is zero, as it is the reference state. However, for monatomic oxygen ($O(g)$), it is non-zero due to the energy needed to break the $O_2$ bond.
$\Delta_f H_{500}^\ominus$ is zero for $O_2(g)$: This statement is correct. $\Delta_f H_{500}^\ominus$ denotes the standard enthalpy of formation at 500 K. Since $O_2(g)$ is the reference state for elemental oxygen, its standard enthalpy of formation is zero at all temperatures, including 500 K.

Based on this analysis, the correct statement is: $\Delta_f H_{500}^\ominus$ is zero for $O_2(g)$. This aligns with $O_2(g)$ being the natural standard state for elemental oxygen.

Answer 2

The objective is to identify the correct statement concerning standard states and enthalpies of formation. Each option will be assessed according to established chemical principles:

The term 'standard state' implies a temperature of $0^\circ C$: ^{}\right\wing This is incorrect. The standard state is a reference condition for thermodynamic calculations, not defined by a specific temperature. While 25°C (298 K) is frequently used, it is not the definition of the standard state.
The standard state of a pure gas is the pure gas at 1 bar pressure and 273 K: This statement is partially incorrect. The standard state for a gas is defined as the pure gas at 1 bar pressure. However, a fixed temperature like 273 K is not mandated; standard enthalpies are typically recorded at 298 K, not 273 K.
$\Delta_f H_{298}^\ominus$ is zero for O(g): This is incorrect. $\Delta_f H_{298}^\ominus$ represents the standard enthalpy of formation. For diatomic oxygen ($O_2(g)$), the standard enthalpy of formation is zero, as it is the reference state. However, for monatomic oxygen ($O(g)$), it is non-zero due to the energy needed to break the $O_2$ bond.
$\Delta_f H_{500}^\ominus$ is zero for $O_2(g)$: This statement is correct. $\Delta_f H_{500}^\ominus$ denotes the standard enthalpy of formation at 500 K. Since $O_2(g)$ is the reference state for elemental oxygen, its standard enthalpy of formation is zero at all temperatures, including 500 K.

Based on this analysis, the correct statement is: $\Delta_f H_{500}^\ominus$ is zero for $O_2(g)$. This aligns with $O_2(g)$ being the natural standard state for elemental oxygen.

The correct statement amongst the following is :

Show Hint

The Correct Option is D

Solution and Explanation

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