381.

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

• 10.0

• 9.0

• 6.0

• 8.0

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

• HCl

• H₂SO₄

• HSO${}_3^{-}$

• SO₃

Conjugate acid of HF${}_2^{-}$ is

• H⁺

• HF

• F${}_2^{-}$

• H₂F₂

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

• H₂SO₄ + H₂O → H₃O⁺ + HSO${}_4^{-}$

• H₂O + H₂O → H₃O⁺ + OH^-

• H₂O + NH${}_2^{-}$ → NH₃ + OH^-

• H₂O + NH₃ → NH${}_4^{+}$ + OH^-

Which of the following is not a equilibrium ?

• Ice $\rightleftharpoons$ Water

• I₂(s) $\rightleftharpoons$ I₂(g)

• S (l) $\rightleftharpoons$ S (g)

• 3O₂ $\rightleftharpoons$2O₃

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

Which of the following oxides is amphoteric in character?

• SnO₂

• SiO₂

• CO₂

• CaO

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

• 7.02

• 7.0

• 6.89

• 6.0

Which of the following is not a buffer ?

• NH₃ + HCl

• CH₃COOH + NaOH

• HCOOH + HCOOK

• NaOH + NaNO₃

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

• 5

• 7

• 1

• pK_a