In which of the following processes does the entropy of the system decrease? I. Freezing of water to ice at 0^ C II. N ₂( g ) + 3 H ₂( g ) 2 NH ₃( g ) III. Dissolution of solid NaCl in water IV. Heating an ideal gas from 300 K to 500 K at constant volume Choose the correct answer from the options given below:

Step-by-step solution

Evaluate the entropy change ( S ) for each process: I. Freezing of water to ice involves a phase change from liquid to solid. The molecules become more ordered, so entropy decreases ( S II. In the reaction N ₂( g ) + 3 H ₂( g ) 2 NH ₃( g ) , the number of gaseous moles decreases from 4 to 2. This leads to a decrease in randomness, so entropy decreases ( S III. Dissolution of solid NaCl in water breaks the crystalline lattice into free-moving aqueous ions, increasing randomness. Thus, entropy increases ( S > 0 ). IV