The amount of the heat released when 20 mL 0.5 M NaOH is mix

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 Multiple Choice QuestionsMultiple Choice Questions

391.

Which of the following is correct?

  • Evaporation of water causes an increase in disorder of the system

  • Melting of ice causes a decrease in the randomness of the system

  • Condensation of steam causes an increase in disorder of the system

  • There is practically no change in the randomness of the system when water is evaporated


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392.

The amount of the heat released when 20 mL 0.5 M NaOH is mixed with 100 ml 0.1 M HCl is x kJ. The heat of neutralisation is:

  • - 100 x kJ/mol

  • - 50 x kJ/mol

  • + 100 x kJ/mol

  • + 50 x kJ/mol


A.

- 100 x kJ/mol

Millimoles (or milliequivalents) of NaOH = 20 x 0.5 = 10

Millimoles (or milliequivalents) of HCl = 100 x 0.1 = 10

 NaOH10milliequivalents + HCl10milliequivalents  NaCl + H2O

Thus, heat released when 10 milliequivalents of HCl are. neutralised by 10 millimoles of NaOH = x kJ. But the heat of neutralisation is heat released when 1 equivalent of HCl is neutralised by 1 equivalent of NaOH.

 neuH = - x10 × 10-3 or - 100 x kJ/mol


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393.

For a spontaneous process, the correct statement(s) is (are)

  • (Gsystem)T, p > 0

  • (Ssystem) + (Ssurroundings) > 0

  • (Gsystem)T, p < 0

  • (Usystem)t, v > 0


394.

The second law of thermodynamic says that in a cyclic process

  • work cannot be converted into heat

  • heat cannot be converted into work

  • work cannot be completely converted into heat

  • heat cannot be completely converted into work


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395.

Equal volumes of molar hydrochloric acid 'and sulphuric acid are neutralized by dilute NaOH solution and x kcal and y kcal of heat are liberated respectively. Which of the following is true ?

  • x = y

  • x =y/2

  • x = 2y

  • none of these


396.

Which of the following thermodynamic relation is correct ?

  • dG = Vdp- SdT

  • dE = pdV + TdS

  • dH = -Vdp + Tds

  • dG = Vdp + SdT


397.

Calculate Kc for the reversible process given below if Kp = 167 and T = 800°C

CaCO3 (s)  CaO (s) + CO2 (g)

  • 1.95

  • 1.85

  • 1.89

  • 1.60


398.

For which reaction change of entropy will be positive?

  • H2(g) + I2(g)  2HI (g)

  • HCl (g) + NH3 (g)  NH4Cl (s)

  • NH4NO3 (s)  N2O (g) + 2H2O (g)

  • MgO(s) + H2(g)  Mg(s) + H2O(l)


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399.

The product p of the nuclear reaction

U92235 + n01  p + Kr3692 + 3n01, is

  • Sr56141

  • La56141

  • Ba56141

  • Cs56141


400.

Which is correct for an enothermic reaction?

  • H is positive

  • H is negative

  • E is negative

  • H= zero


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