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51.

Temperature of `1mol` of a gas is increased by `1^(@)` at constant pressure. The work done isA. `R`B. `2R`C. `R//2`D. `-R`

Answer» Correct Answer - 4
`DeltaW=-PDeltaV=-nRT=-1R(1)=-R`
Discussion
52.

Match the following processes with entropy change:ReactionEntropy change(i) A liquid vapourises ΔS = 0(ii) Reaction is non-spontaneous at all temperatures and ΔH is positive(b) ΔS = positiveiii) Reversible expansion of an(c) ΔS = negative

Answer» (i) →(b) (ii) → (c) (iii) → (a)
Discussion
53.

Match the following :AB(i) Adiabatic process(a) Heat(ii) Isolated system(b) At constant volume(iii) Isothermal change(c) First law of thermodynamics(iv) Path function(d) No exchange of energy and matter(v) State function(e) No transfer of heat(vi) ΔU = q(f) Constant temperature(vii) Law of conservation of energy(g) Internal energy(viii) Reversible process(h) pext = 0(ix) Free expansion(i) At constant pressure(x) ΔH = q(j) Infinitely slow process which proceeds through a series of equilibrium states.(xi) Intensive property(k) Entropy(xii) Extensive property(l) Pressure(m) Specific heat

Answer» (i) → (e) (ii) → (d) (iii) → (f) (iv) → (a)

(v) → (g), (k), (l) (vi) → (b) (vii) → (c) (viii) → (j)

(ix) → (h) (x) → (i) (xi) → (a), (l), (m) (xii) → (g), (k)
Discussion
54.

In an adiabatic process, no transfer of heat takes place between system and surroundings. Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following.(i) q = 0, ΔT ≠ 0, w = 0(ii) q ≠ 0, ΔT = 0, w = 0(iii) q = 0, ΔT = 0, w = 0(iv) q = 0, ΔT < 0, w ≠ 0

Answer»

(iii) q = 0, ΔT = 0, w = 0

Justification : free expansion w = 0   adiabatic process q = 0

ΔU = q + w = 0, this means that internal energy remains constant. Therefore, ΔT = 0.

In expands under adiabatic conditions into a vaccum no heat is absorbed or evolved since no external work is done to separate the molecules.ideal gas there is no intermolecular attraction. Hence when such a gas 
Discussion