Which one of the following statements is true? from Chemistry Th

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 Multiple Choice QuestionsMultiple Choice Questions

171.

Standard enthalpies of formation of O3, CO2, NH3 and HI are 142.2, -393.2,- 46.2 and 25.9 kJ mol-1 respectively. Decreasing order of their stability is

  • HI > NH3 > CO2 > O3

  • NH3 > CO2 > HI > O3

  • CO2 > NH3 > HI > O3

  • O3 > HI > NH3 > CO2


172.

First and second ionisation enthalpies of Mg are 737. 76 and 1450.73 J mol-1 respectively. The energy required to convert all the atoms of magnesium to magnesium ions present in 24g of magnesium vapours is

  • 24 kJ

  • 2.188 kJ

  • 12 kJ

  • 4.253 kJ


173.

The standard enthalpy of vapourisation Δvap H° for water at 100°C is 40.66 kJ mol-1. The internal energy of vapourisation of water 100°C (in kJ mol-1) is (assume water vapour to behave like an ideal gas).

  • + 4376

  • +40.66

  • +37.56

  • None of these


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174.

Which one of the following statements is true?

  • E ia always greater than H

  • E is always less than H

  • E may be lesser or greater or equal to H

  • E is always proportional to H


C.

E may be lesser or greater or equal to H

E may be greater or lesser or equal to H. Since,

H = E + PV = E + n RT

If n > 0, then H > E

If n < 0, then H < E

For solids and liquids, H = E


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175.

The intensive property among these quantities is

  • enthalpy

  • mass/ volume

  • mass

  • volume


176.

If the adsorption of a gas on solid metal surface is spontaneous and exothermic, then

  • H increases

  • S increases

  • G increases

  • S decreases


177.

30g of Mg and 30g of oxygen are reacted and the residual mixture contains

  • 45 g of MgO and 15 g of O2

  • 50 g of MgO and 10 g of O2

  • 60 g of MgO only

  • 40 g of MgO and 20 g of O2


178.

Compounds with high heat of formation are less stable because

  • high temperature is required to synthesise them

  • molecules of such compounds are distorted

  • it is difficult to synthesise them

  • energy rich state leads to instability


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179.

Enthalpy of formation of HF and HCl are -161 kJ and -92 kJ respectively. Which of the following statements is incorrect?

  • HCl is more stable than HF

  • HF and HCl are exothermic compounds

  • The affinity of fluorine to hydrogen is greaterthan the affinity of chlorine to hydrogen

  • HF is more stable than HCl


180.

The enthalpy of reaction,

H2(g) +12O2(g)  H2O(g) isH1 and that of H2(g) +12O2(g)  H2O(l) isH2.Then

  • ΔH1 < ΔH2

  • ΔH1 + ΔH2 = 0

  • ΔH1 > ΔH2

  • ΔH1 = ΔH2


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