In which of the following reactions, standard reaction entropy c

Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

pH of a saturated solution of Ba(OH)2 is 12. The value of solubility product Ksp of Ba(OH)2 is

  • 3.3 x 10-7

  • 5.0 x 10-7

  • 4.0 x 10-6

  • 4.0 x 10-6

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2.

Maximum number of electrons in a subshell with l =3 and n=4 is

  • 14

  • 16

  • 10

  • 10

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3.

In which of the following reactions, standard reaction entropy changes (ΔSo) is positive and standard Gibb's energy change (ΔGo) decreases sharply with increasing temperature?

  • C (graphite) +1/2 O2 (g) → CO (g)

  • CO (g) +1/2 (g) → CO2 (g)

  • Mg(s)  +1/2O2 (g) → MgO (s)

  • Mg(s)  +1/2O2 (g) → MgO (s)


A.

C (graphite) +1/2 O2 (g) → CO (g)

Among the given reactions only in te case of 
C (graphite) +1/2 O2 (g) → CO (g)
entropy increases because randomness (disorder) increases. Thus, standard entropy change (ΔSo) is positive.
Moreover, it is a combustion reaction and all the combustion reactions are generally exothermic, ie. ΔHo=-ve
We know that
ΔGo = ΔHo-TΔSo

ΔGo = -ve-T(+ve)
Thus, as the temperature increases, the value of ΔGo decreases.

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4.

Equimolar solutions of the following substances were prepared separately, which one of these will record the highest pH value?

  • BaCl2

  • AlCl3

  • LiCl

  • LiCl

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5.

50 mL of each gas A and of gas B takes 150 and 200 s respectively for effusing through a pin hole under the similar conditions. If molecular mass of gas B is 36, the molecular mass of gas A will be

  • 96

  • 128

  • 20.2

  • 20.2

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6.

The correct set four quantum number for the valence electron of rubidium atom (z=37) is 

  • 5,1,1, +1/2

  • 6,0,0,+1/2

  • 5,0,0 +1/2

  • 5,0,0 +1/2

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7.

Buffer solutions have constant acidity and alkalinity because

  • these give unionised acid or base on reaction with added acid or alkali

  • acids and alkalies in these solutions are shielded from attack by other ions.

  • they have a large excess of H+ or OH- ions

  • they have a large excess of H+ or OH- ions

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8.

The enthalpy of fusion of water is 1.435 Kcal/mol. The molar entropy change for the melting of ice of at 0o C is

  • 10.52 cal/(mol K)

  • 21.04 cal/(mol K)

  • 5.260 cal/ (mol K)

  • 5.260 cal/ (mol K)

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9.

Bond order of 1.5 is shown by

  • O2+

  • O2-

  • O22-

  • O22-

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10.

Standard enthalpy of vaporisation ΔvapHθ for water for water at 100oC is 40.66 kJ mol-1. The internal energy of vaporisation of water at 100o C (in KJ mol-1) is

(Assume water vapour to behave like an ideal gas.)

  • +37.56

  • -43.76

  • +43.76

  • +43.76

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