Question

An aqueous solution is prepared to be 0.31S M in sodium fluoride and 0.190 M in acetic acid. Is this solution a buffer solution? What is the pi I of this solution? If 0.119 moles of nitric acid are added to one liter of this solution, what is the pH of the resulting solution? pH =

Answer 1

Answer:

1) No this solution is not a buffer.

Buffer is prepared by mixing an appropriate concentratins of a weak acid and salt of the same weak acid.

Acetic acid AcOH is a weak acid but Sodium fluoride (NaF) is a salt of strong base NaOH and strong acd HF.

Addition of NaF will just increase ionic stregth of AcOH and there will be complete ionization of AcOH

as,

AcOH + NaF ------> AcONa + HF

HF being strong acid ionizes completely as

HF --------> H⁺ (aq) + F^- (aq)

[H⁺] = [AcOH] = 0.190 M = 0.190 mole / L

Hence,

pH = -log([H⁺])

pH = -log(0.190)

pH = 0.72

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c) Addition of a strong monoprotic HNO3 acid there will be increse in concentration of H+ ions.

[H⁺] = [HNO₃] = 0.119 moles.

Assuming no change in volume,

New moles of H⁺ = 0.190 moles + 0.119 moles

New moles of H⁺ = 0.309 moles.

New [H⁺] = 0.309 moles / 1L = 0.309M

pH = -log(0.309)

pH = 0.51

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