Question

You are dealing with the chemicals nitrous acid (HNO₂) and sodium nitrite (NaNO₂). Nitrous acid has a pK_a of 3.398 and a K_a of 4.00 x 10^-4

a) Could mixing the “ right amounts ” of nitrous acid with sodium nitrite together in water create a buffer solution ? Briefly explain, including what it means to have the “ right amounts ".

b) What would be the effective pH range of this buffer?

c) Instead of using a compound containing nitrite ion like sodium nit rite, the buff er could be made by mixing nitrous acid with what kind of other chemical? Give an example.

d) Conversely, instead of using nitrous acid, the buffer can also be made by mixing sodium nitrite with what type of other chemical?

Answer 1

a) yes, it will form an acidic buffer since it is a combination of weak acid HNO₂ and salt of its strong conjugate base NaNO₂.

According to Henderson's equation, as long as [HNO₂] = 10[NaNO₂] to10[HNO₂] = [NaNO₂] . within this limit a good buffer can be formed in which pH= pKa1.

b) pH = 3,398 1

c) Any chemical capable of producing nitrite ion(NO₂^-) e.g NH₄NO₂

d) NH₄Cl + NaNO₂ NH₄NO₂ + NaCl. NH₄NO₂ is a salt of weak acid and weak base which can also act as buffer.