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  | Thermodynamics

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 Multiple Choice QuestionsMultiple Choice Questions

11.

The solubility product of silver bromide is 5.0 x 10-13. The quantity of potassium bromide (molar mass taken as 120 g mol–1)to be added to 1 litre of 0.05 M solution of silver nitrate to start the precipitation of AgBr is

  • 1.2 x 10-10

  • 1.2 x 10-9 g

  • 6.2 x 10-5

  • 6.2 x 10-5

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12.

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 

  • Te>T

  • T >Te

  • Te is 5 times T

  • Te is 5 times T


A.

Te>T

For a particular reversible reaction at T temperature
ΔG = ΔH-TΔS
When ΔH, S is positive
ΔG = +ΔH- T (+ΔS)
For a spontaneous process, ΔG must be negative, it is possible only at high temperature.
That mean T> Te

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13.

Δ U is equal to

  • Isochoric work

  • Isobaric work

  • Adiabatic work

  • Adiabatic work

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14.

Given
C(grahite) + O2(g) → CO2(g)
ΔrH°  = - 393.5 kJ mol-1
H2(g) + 1/2O2(g) → H2O (l)
ΔrH°  = +890.3 kJ mol-1
Based on the above thermochemical equations, the value of ΔrH° 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

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15.

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%

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16.

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

208 Views

17.

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

1 half Cl subscript 2 space left parenthesis straight g right parenthesis space rightwards arrow with 1 half space increment subscript diss straight H to the power of minus on top space Cl space left parenthesis straight g right parenthesis space rightwards arrow with increment subscript eg straight H to the power of minus on top space Cl to the power of minus space left parenthesis straight g right parenthesis space rightwards arrow with increment subscript hyd straight H to the power of minus on top Cl to the power of minus space left parenthesis aq right parenthesis
The energy involved in conversion of 1 half Cl subscript 2 space left parenthesis straight g right parenthesis space to space Cl to the power of minus space left parenthesis straight g right parenthesis

left parenthesis using space the space data comma space increment subscript diss straight H subscript cl subscript 2 end subscript superscript minus space equals space 240 space kJ space mol to the power of minus comma space increment subscript eg space straight H subscript cl superscript minus space equals space minus space 349 space kJ space mol to the power of minus comma space
increment subscript eg space straight H subscript cl superscript minus space equals space minus 381 space kJ space mol to the power of minus right parenthesis

  • 152 kJ mol-

  • -610 kJ mol-

  • -850  kJ mol-

  • -850  kJ mol-

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18.

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

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19.

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

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20.

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

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