Thermodynamics

The state is thermodynamically unstable and tends to freeze into ice spontaneously.

Step 1: Understanding the Concept:
The sign of the enthalpy change indicates whether the reaction is endothermic or exothermic. Le Chatelier's principle states that increasing temperature favors the endothermic direction.

Step 2: Detailed Explanation:
The reaction is given as . The "+14.6 kcal" on the right side means the forward reaction (formation of N O ) is exothermic. The reverse reaction (decomposition of N O ) is endothermic. According to Le Chatelier's principle, an increase in temperature favors the endothermic direction, i.e., the decomposition of N O .

Step 3: Final Answer:
An increase in temperature favors the decomposition of N O , which corresponds to option (B).

Step 1: Understanding the Concept:
Spontaneity of a process is determined by Gibbs free energy change: . For spontaneity, .
Step 2: Detailed Explanation:
\begin{itemize} \item (A) : is negative at low temperatures, positive at high temperatures. Spontaneous only at low temperatures. \item (B) : is always positive. Non-spontaneous at all temperatures. \item (C) : is always negative. Spontaneous at all temperatures. \item (D) : is negative at high temperatures, positive at low temperatures. Spontaneous only at high temperatures. \end{itemize}
Step 3: Final Answer:
The condition for spontaneity at all temperatures is and , option (C).

Step 1: Understanding the Concept:
The relationship between standard Gibbs free energy change and equilibrium constant is .
Step 2: Detailed Explanation:
Given: , , . .
Step 3: Final Answer:
, option (B).

Step 1: Understanding the Concept:
Gibbs free energy change determines spontaneity.
Step 2: Detailed Explanation:
For a spontaneous process at constant temperature and pressure, .
Step 3: Final Answer:
must be negative.

Step 1: Understanding the Concept:
.
Step 2: Detailed Explanation:
J K mol .
Step 3: Final Answer:
Entropy of vaporisation is J K mol .

Step 1: Understanding the Concept:
.
Step 2: Detailed Explanation:
cal K .
Step 3: Final Answer:
Entropy change is 2 cal K .

Step 1: Understanding the Concept:
.
Step 2: Detailed Explanation:
.
Step 3: Final Answer:
.