Chemistry - Thermodynamics - II Question with Solution | TestHub
Consider the following phase transitions:
(i) H2O (l, 1 atm, 373 K) → H2O (g, 1 atm, 373 K)
(ii) H2O (l, 1 atm, 380 K) → H2O (g, 1 atm, 380 K)
(iii) H2O (l, 1 atm, 350 K) → H2O (g, 1 atm, 350 K)
(iv) H2O (l, 2 atm, 373 K) → H2O (g, 2 atm, 373 K)
(v) H2O (l, 0.5 atm, 373 K) → H2O (g, 0.5 atm, 373 K)
(vi) H2O (s, 1 atm, 260 K) → H2O (l, 1 atm, 260 K)
(vii) H2O (s, 1 atm, 273 K) → H2O (l, 1 atm, 273 K)
(viii) H2O (s, 1 atm, 290 K) → H2O (l, 1 atm, 290 K)
(ix) H2O (l, 1 atm, 260 K) → H2O (s, 1 atm, 260 K)
The normal boiling point of water is 373 K and its normal freezing point is 273 K.
Answer:
Solution:
Equilibrium: (i), (vii), so a = 2. Spontaneous: (ii) above the boiling point; (v) at 0.5 atm water boils below 373 K; (viii) above the melting point; (ix) supercooled water at 260 K freezes spontaneously; b = 4. Non-spontaneous: (iii) below the boiling point; (iv) at 2 atm water boils above 373 K; (vi) ice below its melting point does not melt; c = 3. Δ H > 0 for melting and vaporization, (i) to (viii), but (ix) is freezing (Δ H<0); d = 8. abcd = 2438.
