If  Hf (H2O) is -286.20 kJ mol-1, then  Hf°&nb

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 Multiple Choice QuestionsMultiple Choice Questions

241.

The enthalpy of combustion for the H2, cyclohexene and cyclohexane are -241, -3800 and -3920 kJ mol-1 respectively. Heat of hydrogenation of cyclohexene is

  • 121 kJ mol-1

  • -121 kJ mol-1

  • 242 kJ mol-1

  • -242 kJ mol-1


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242.

If  H(H2O) is -286.20 kJ mol-1, then  Hf°  (OH-) is

  • -228.88 kJ mol-1

  • +228.88 kJ mol-1

  • -343.52 kJ mol-1

  • +343.52 kJ mol-1


A.

-228.88 kJ mol-1

H+ + OH- → H2O,  H = -57.3 kJ mol-1 (standard value)

 H =   f (H2O) -  H°f (H+) -  f (OH-)

-57.3 = -286.2 - 0 - f (OH-)

 f (OH-) = -228.9 kJ mol-1


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243.

1 mole of gas occupying 3 L volume is expanded against a constant external pressure of 1 atm to a volume of 15 L. The work done by a system is equal to

  • -1.215 × 103 J

  • -12.15 × 103 J

  • +1.215 × 103 J

  • +12.15 × 103 J


244.

Which one of the following is not a state function?

  • Internal energy

  • Work

  • Entropy

  • Free energy


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245.

Given that N2(g) + 3H2(g) → 2NH3(g): ΔrH° =-92kJ, the standard molar enthalpy of formation in kJ mol-1 of NH3(g) is 

  • -92

  • +46

  • +92

  • -46


246.

In view of rG° for the following reactions

PbO2 + Pb → 2PbO, rG°r

SnO2 + Sn → 2SnO, rG°r

Which oxidation state is more characteristic for lead and tin?

  • For lead +2, for tin +2

  • For lead +4, for tin +4

  • For lead +2, for tin +4

  • For lead +4, for tin +2


247.

The enthalpy of the formation of CO2 and H2O are -395 kJ and -285 kJ respectively and the enthalpy of combustion of acetic acid is 869 kJ. The enthalpy of formation of acetic acid is

  • 340 kJ

  • 420 kJ

  • 491 kJ

  • 235 kJ


248.

Considering entropy(s) as a thermodynamic parameter, the criterion for the spontaneity of any process, the change in entropy is

  • Ssystem >0 only

  • Ssurrounding > 0

  • Ssystem + Ssurrounding > 0

  • (Ssystem - Ssurrounding) > 0


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249.

Standard enthalpy (heat) of formation of liquid water at 25°C is around

 H2(g) + 12O2(g) → H2O (l)

  • -237 kJ/mol

  • 237 kJ/mol

  • - 286 kJ/mol

  • 286 kJ/mol


250.

Given ΔHf° for CO2(g) , CO(g) and H2O(g) are -393.5, -110.5 and -241.8 kJ mol-1, respectively. The ΔHf° [in kJ mol-1] for the reaction

CO2(g) + H2(g) → CO(g) + H2O (g) is

  • 524.1

  • -262.5

  • -417

  • 412


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