The pH of 10-8 M NaOH aqueous solution at 25°C, is from

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 Multiple Choice QuestionsMultiple Choice Questions

381.

A buffer solution is prepared by mixing 0.1 M ammonia and 1.0 M ammonium chloride. At 298 K, the pKb of NH4OH is 5.0. The pH of the buffer is

  • 10.0

  • 9.0

  • 6.0

  • 8.0


382.

Which of the following behaves as Lewis acid and not as Bronsted acid ?

  • HCl

  • H2SO4

  • HSO3-

  • SO3


383.

Conjugate acid of HF2- is

  • H+

  • HF

  • F2-

  • H2F2


384.

Water is well known amphoprotic solvent. In which chemical reaction water is behaving as a base?

  • H2SO4 + H2O → H3O+ HSO4-

  • H2O + H2O → H3O+ + OH-

  • H2O + NH2- → NH+ OH-

  • H2O + NH3 → NH4+ + OH-


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385.

Which of the following is not a equilibrium ?

  • Ice  Water

  • I2(s)  I2(g)

  • S (l)  S (g)

  • 3O2 2O3


386.

The standard emf of a cell, involving one electron change is found to be 0.591 V at 25°C. The equilibrium constant of the reaction is (F = 96500 C mol-1)

  • 1.0 × 101

  • 1.0 × 105

  • 1.0 × 1010

  • 1.0 × 1030


387.

Which of the following oxides is amphoteric in character?

  • SnO2

  • SiO2

  • CO2

  • CaO


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388.

The pH of 10-8 M NaOH aqueous solution at 25°C, is

  • 7.02

  • 7.0

  • 6.89

  • 6.0


A.

7.02

[OH-] of NaOH = 10-8M

Since, the concentration of OH- obtained from NaOH is very low, the concentration of OH-  water cannot be neglected. Thus,

Total [OH-] = [OH-]NaOH + [OH-]H2O

  = 10-8 + 10-7

 = 10-7 (1.1) = 1.1 × 10-7

pOH = -log[OH-]

       = -log (1.1 × 10-7 ) = 6.96

pH = 14-6.69 = 7.04


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389.

Which of the following is not a buffer ?

  • NH3 + HCl

  • CH3COOH + NaOH

  • HCOOH + HCOOK

  • NaOH + NaNO3


390.

The buffering action of an acidic buffer is maximum when its pH is equal to

  • 5

  • 7

  • 1

  • pKa


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