Question

5. Describe three different methods that can be used to get a buffer solution to a particular pH (specifically consider how an acid/base/concentration of ions can be used to calculate the pH). А. В. С. AL Ci

Answer 1

(A)

A buffer can be formed by mixing two solutions of weak acid (HA) and it's salt (NaA) .

pH = pKa + log([salt]/[acid])

(B)

A buffer can be formed by mixing a solution of weak acid and a strong base (NaOH, in limited amount )

HA + NaOH(less amount) $\rightarrow$ NaA + H₂O

Let x mol of NaOH is added to y mol of HA. (y > x)

pH = pKa + log(x/(y-x))

(C)

A buffer can be formed by addition of strong acid (in limited amount) to a solution of salt of weak acid (NaA)

NaA + HCl(less amount)  $\rightarrow$ HA + NaCl

Let x mol of HCl is added to y mol of NaA solution .( x < y)

pH = pKa + log((y-x)/x)