A gas is allowed to expand in a well-insulated container against

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 Multiple Choice QuestionsMultiple Choice Questions

281.

Given that bond energy of H-H and Cl- Cl are 430 kJ mol-1 and 240 kJ mol-1 respectively and ΔHf for HCl is -90 kJ mol-1. Bond and ΔHf for HCl is -90 kJ mol-1.Bond enthalpy of HCl is:

  • 290 kJ mol-1

  • 380 kJ mol-1

  • 425 kJ mol-1

  • 425 kJ mol-1


282.

Assume each reaction is carried out in an open container. For which reaction will ΔH = ΔE?

  • H2 (g) + Br2 (g) →2HBr (g)

  • C (s) + 2 H2O (g) → 2 H2 (g) + CO2 (g)

  • PCl5 (g) →PCl3 (g) + Cl2 (g) 

  • PCl5 (g) →PCl3 (g) + Cl2 (g) 

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283.

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

  • -212 kJ mol

  • +121 kJ mol

  • +242 kJ per mol

  • +242 kJ per mol

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284.

A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy ΔU of the gas in joules will be

  • 1136.5 J

  • -500 J

  • -505 J

  • -505 J


C.

-505 J

ΔU = q + w
For adiabatic process, q = 0
∴ ΔU = w
= – P·ΔV
= –2.5 atm × (4.5 – 2.5) L
= –2.5 × 2 L-atm
= –5 × 101.3 J
= –506.5 J
= –505 J

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285.

For a given reaction, ΔH = 35.5 kJ mol–1 and ΔS = 83.6 JK–1 mol–1. The reaction is spontaneous at (Assume that ΔH and ΔS do not vary with temperature)

  • T < 425 K

  • T > 425 K

  • All temperatures

  • All temperatures

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286.

Consider the change in oxidation state of Bromine corresponding to different emf values as shown in the diagram below :

BrO4- 1.82BrO3-1.5 VHBrO1.595Br21.0652 VBr-

Then the species undergoing disproportionation is

  • BrO3-

  • BrO4-

  • HBrO

  • Br2


287.

Which one of the following conditions will favour maximum formation of the product in the reaction,

A2 (g) + B2 (g)       X2 (g)r H = - XkJ?

  • Low temperature and high pressure

  • Low temperature and low pressure

  • High temperature and low pressure

  • High temperature and high pressure


288.

The bond dissociation energies of X2, Y2 and XY are in the ratio of 1 : 0.5: 1. ΔH for the formation of XY is –200 kJ mol–1. The bond dissociation energy of X2 will be

  • 200 kJ mol-1

  • 100 kJ mol-1

  • 400 kJ mol-1

  • 800 kJ mol-1


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289.

The correction factor ‘a’ to the ideal gas equation corresponds to

  • Density of the gas molecules

  • Volume of the gas molecules

  • Forces of attraction between the gas molecules

  • Electric field present between the gas molecules


290.

The energy released when 6 moles of octane is burnt in air will be [Given, ΔHf for CO2 (g). H2O(g) and C8H18 (l), respectively are -490, -240 and +160J/mol]

  • -37.4 kJ

  • -20 kJ

  • -6.2 kJ

  • -35.5 kJ


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