a.
\(c_\mathrm{syra} = [\mathrm{HAc}]\); \(c_\mathrm{bas} = [\mathrm{Ac^-}]\)
\[\begin{aligned}\mathrm{pH} &= \mathrm{p}K_\mathrm{a} - \lg\left(\frac {c_\mathrm{syra}}{c_\mathrm{bas}} \right) = \\ &= 4,77 - \lg\left(\frac {0,010\mathrm{M}}{0,050\mathrm{M}} \right) = 5,46897000 ≈ 5,47 \end{aligned}\]
b.
\(c_\mathrm{syra} = [\mathrm{NH_4^+}]\); \(c_\mathrm{bas} = [\mathrm{NH_3}]\)
\[\begin{aligned}\mathrm{pH} &= \mathrm{p}K_\mathrm{a} - \lg\left(\frac {c_\mathrm{syra}}{c_\mathrm{bas}} \right) = \\ &= 9,24 - \lg\left(\frac {0,15\mathrm{M}}{0,25\mathrm{M}} \right) = 9,46184875 ≈ 9,46 \end{aligned}\]
c.
\(c_\mathrm{syra} = [\mathrm{H_2S}]\); \(c_\mathrm{bas} = [\mathrm{HS^-}]\)
\[\begin{aligned}\mathrm{pH} &= \mathrm{p}K_\mathrm{a} - \lg\left(\frac {c_\mathrm{syra}}{c_\mathrm{bas}} \right) = \\ &= 9,24 - \lg\left(\frac {0,45\mathrm{M}}{0,15\mathrm{M}} \right) = 6,57287875 ≈ 6,57 \end{aligned}\]
