Thermodynamics

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

• T_e>T

• T >T_e

• T_e is 5 times T

• T_e is 5 times T

Δ U is equal to

• Isochoric work

• Isobaric work

• Adiabatic work

• Adiabatic work

Given
C(grahite) + O₂(g) → CO₂(g)
Δ_rH°  = - 393.5 kJ mol^-1
H₂(g) + 1/2O₂(g) → H₂O (l)
Δ_rH°  = +890.3 kJ mol^-1
Based on the above thermochemical equations, the value of Δ_rH° at 298 K for the reaction
C(grahite) + 2H₂(g) →CH₄ will be

•  +74.8 kJ mol^–1 

• +144.0 kJ mol^–1

• –74.8 kJ mol^–1

• –74.8 kJ mol^–1

In a fuel cell methanol is used as fuel and oxygen gas is used as an oxidizer. The reaction is
CH₃OH(l) + 3/2O₂(g) → CO₂(g) + 2H₂O(l)
At 298 K standard Gibb’s energies of formation for CH₃OH(l), H₂O(l) and CO₂(g) are –166.2, –237.2 and –394.4 kJ mol^–1 respectively. If
standard enthalpy of combustion of methanol is –726 kJ mol^–1, efficiency of the fuel cell will be:

• 80%

• 97%

• 87%

• 87%

Which one of the following reactions of Xenon compounds is not feasible?

• XeO₃+ 6HF → XeF₆  + 3H₂O

• 3XeF₄ +6H₂O → Xe+XeO₃+ 12HF+ 1.5O₂

• 2XeF₂ + 2H₂O → 2Xe + 4HF +O₂

• 2XeF₂ + 2H₂O → 2Xe + 4HF +O₂

Oxidising power of chlorine in aqueous solution can be determined by the parameters indicated below


The energy involved in conversion of 

• 152 kJ mol^-

• -610 kJ mol^-

• -850  kJ mol^-

• -850  kJ mol^-

Standard entropy of X₂, Y₂ and XY₃ are 60, 40 and 50 JK⁻¹
mol −1, respectively. For the reaction,1/2X₂ + 3/2Y₂, ΔH = -30 kJ,to be at equilibrium, the temperature will be

• 1250 K

• 500 K 

• 750 K

• 750 K

In the reaction,
2Al(s) + 6HCl(aq) → 2Al³⁺ (aq) + 6Cl¯(aq) + 3H₂(g)

• 6L HCl(aq) is consumed for every 3L H₂(g) produced

• 33.6 L H₂(g) is produced regardless of temperature and pressure for every mole Al that reacts

• 67.2 L H₂(g) at STP is produced for every mole Al that reacts

• 67.2 L H₂(g) at STP is produced for every mole Al that reacts

Identify the correct statement regarding a spontaneous process –

• For a spontaneous process in an isolated system, the change in entropy is positive

• Endothermic processes are never spontaneous

• Exothermic processes are always spontaneous

• Exothermic processes are always spontaneous

In the conversion of limestone to lime, CaCO₃(s) → CaO(s) + CO₂(g) the values of ∆Hº and ∆Sº are + 179.1 kJ mol^–1 and 160.2 J/K respectively at 298K and 1 bar. Assuming that ∆Hº and ∆Sº do not change with temperature, temperature above which conversion of limestone to lime will be spontaneous is

• 1008 K

• 1200 K

• 845 K

• 845 K