A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of 37.0ºC. As it does so, it absorbs 208 J of heat. The values of q and w for the process will be:(R = 8.314 J/mol K) (ln 7.5 = 2.01)

q= + 208 J, w = – 208 J
q = – 208 J, w =– 208 J
q= – 208 J, w = + 208 J
q= + 208 J, w = + 208 J

Solution

Process is isothermal reversible expansion,
hence ΔU = 0, therefore q = – W.Since q = +208 J, W= –208 J

Solution

The species which by definition has ZERO standard molar enthalpy of formation at 298 K is

Br₂(g)
Cl₂(g)
H₂O(g)
CH₄(g)

Solution

The species in its elemental form has zero standard molar enthalpy of formation at 298 K. At 298K, Cl₂ is gas while Br₂ is liquid.

For the process H₂O(l) (1 bar, 373 K) ⟶ H₂O(g) (1 bar,373K), the correct set of thermodynamic parameters is

ΔG= 0, ΔS= +ve
ΔG= 0, ΔS = –ve
ΔG= +ve, ΔS= 0
ΔG= –ve, ΔS= +ve

Solution

Since, liquid is passing into gaseous phase so entropy will increase and at 373 K during the phase transformation it remains at equilibrium. So, ΔG = 0.

Solution

Solution

For a particular reversible reaction at temperature T, ΔH and ΔS were found to be both +ve. If T_e is the temperature at equilibrium, the reaction would be spontaneous when

T_e > T
T > T_e
T_e is 5 times T
T = T_e

Solution

At equilibrium ΔG = 0
Hence, ΔG= ΔH– TeΔS = 0
ΔH= TeΔS or T_e = \(\frac{\Delta H}{\Delta s}\)
For a spontaneous reaction
ΔG must be negative which is possible only if ΔH– TΔS < 0 ∴ ΔH > TΔS
or T > \(\frac{\Delta H}{\Delta s}\);
T_e < T

Solution

Assuming that water vapour is an ideal gas, the internal energy change (ΔU)when 1 mol of water is vapourised at 1 bar pressure and 100°C, (given : molar enthalpy of vapourisation of water at 1 bar and 373 K = 41 kJ mol^-1 and R = 8.3 J mol^-1 K –1) will be

41.00 kJ mol^-1
4.100 kJ mol^-1
3.7904 kJ mol^-1
37.904 kJ mol^-1

Solution

Given ΔH = 41 kJ mol–1 = 41000 J mol^-1
T = 100°C = 273 + 100 = 373 K
n =1
ΔU = ΔH – ΔnRT = 41000 – (1 × 8.314× 373)
=37898.88 J mol^-1 ≃ 37.9 kJ mol^-1

UnAttempted

0

Attempted

0

Correct

0

Wrong

0

Complete