The enthalpy of combustion at 25°C of H2, cyclohexane (C6H12)

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 Multiple Choice QuestionsMultiple Choice Questions

301.

A reaction occurs spontaneously if

  • TS < H and both H and S are +ve

  • TS > H and both H and S are +ve

  • TS = H and both H and S are +ve

  • TS > H and H is +ve and S is - ve


302.

Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction?

  • Exothermic and decreasing disorder

  • Endothermic and increasing disorder

  • Exothermic and increasing disorder

  • Endothermic and decreasing disorder


303.

The absolute enthalpy of neutralisation of the reaction

MgO(s) + 2HCl(aq)  MgCl2(aq) + H2O(l)

will be

  • less than - 57.33 kJ mol-1

  • - 57.33 kJ mol-1

  • greater than-- 57.33 kJ mol-1

  • 57.33 kJ mol-1


304.

Which of the following have highest electron affinity?

  • F

  • Cl

  • N

  • O


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305.

The enthalpy of combustion at 25°C of H2, cyclohexane (C6H12) and cyclohexene (C6H10) are -241, -3920 and -3800 kJ/mol respectively. The heat of hydrogenation of cyclohexene is :

  • -121 kJ/mol

  • +121 kJ/mol

  • -242 kJ/mol

  • +242 kJ/mol


A.

-121 kJ/mol

The heat of hydrogenation of cyclohexene can be calculated as-

H212 O2 H2O    ;   H = -241 kJ  ...(i)

C6H10172 O2 6CO2 + 5H2O    ; H = -3800 kJ  ...(ii)

C6H12 + 9O2 6CO2 + 6H2O        ; H = -3920 kJ  ...(iii)

Hydrogenation of cyclohexane-

C6H10 + H2 C6H12

Equation (i) + equation (ii) - equation (iii)

H = -241 - 3800 - (-3920)

      = -4041 + 3920

      = - 121 kJ


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306.

The entropy values (in JK-1mol-1) of H(g) = 130.6, Cl(g) = 223.0 and HCl (g) = 186. 7 at 298 K and 1 atm pressure. Then entropy change for the reaction :

H2 ( g)+ Cl(g)  2HCl (g) is:

  • +540.3

  • +727.3

  • -166.9

  • +19.8


307.

Consider the respective enthalpy for the following reactions:

(I) NH3(g) + 3Cl2 (g)  NCl3 (g) + 3HCl (g); -ΔH1(II) N2(g)+ 3H2 (g)2NH3 (g); -ΔH2(III) H2 (g) + Cl2 (g) 2HCl (g); ΔH3

The enthalpy of formation of NCl3 (g) in terms of ΔH1 , ΔH2  , ΔH3 is:

  • ΔHf= -ΔH1 +ΔH22 - 32 ΔH3

  • ΔHf= ΔH1 +ΔH22 - 32 ΔH3

  • ΔHf= -ΔH1 - ΔH22 - 32 ΔH3

  • None of the above


308.

The entropy will be positive in which of the following reaction change.

  • H2(g) + I2 (g)  2HI (g)

  • HCl(g) + NH3 (g)  N2O(g) + 2H2O(g)

  • NH4NO3(s)N2O(g) + 2H2O(g)

  • MgO(s) + H2(g)  Mg(s) + H2O(l)


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309.

C(dia) + O2  CO2H = - 395.4 kJ/ mol

C(gr) + O2 CO2H   = - 393.5 kJ/ mol

C(gr) C(dia)H = ?

  • -3.8

  • -1.9

  • +3.8

  • +1.9


310.

The internal energy of a substance

  • decrease with increase in temperature

  • increase with increase in temperature

  • remains unaffected with change in temperature

  • calculated by E = mc2


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