AP EAPCET 22 May 2025 Shift 1 Paper

Let's analyze each process in terms of entropy change ( ∆S ):
I. Sublimation of dry ice (solid CO2⟶ gas CO2 )
A solid goes directly to a gas.
The disorder (randomness) increases significantly.
Entropy increases ⟶∆S>0
II. Freezing of water (liquid ⟶ solid)
A liquid becomes a more ordered solid structure.
Disorder decreases.
Entropy decreases ⟶∆S<0
III. Crystallisation of the dissolved substance
Dissolved ions/molecules (disordered) form a regular crystal lattice (ordered).
Disorder decreases.
Entropy decreases ⟶∆S<0
IV. Burning of rocket fuel (combustion)
Chemical reaction produces gases and increases randomness overall.
Entropy increases ⟶∆S>0
Processes with negative entropy change:
II. Freezing of water
III. Crystallisation of the dissolved substance
Correct answer: Option B - II and III only