JEE Main201910 Jan 2019Evening ShiftChemistryThermodynamics (C)Actual
The process with negative entropy change is:
Options
- ASynthesis of ammonia from N 2 and H 2 .
- BDissolution of iodine in water.
- CDissociation of CaSO 4   s to CaO   s and SO 3   g .
- DSublimation of dry ice.
Correct answer
A. Synthesis of ammonia from N 2 and H 2 .
Step-by-step solution
If a process leads to the arrangement in a system, it will have a negative entropy, whereas if disorder increases, the entropy will be positive. When the number of moles of a gas increases, or ice melts, the disorder increases. Freezing of water, crystallization, combination reactions etc, leads to an arrangement. CO 2   s → CO 2   g ;   ∆ S = + ve   ∆ n g > 0 N 2   ( g ) + 3 H 2   ( g ) → 2 NH 3 ( g ) ;   ∆ S = - ve   ∆ n g = - ve CaCO