Which mixtures act as buffer solutions?

I.     \({\text{100 c}}{{\text{m}}^{\text{3}}}{\text{ 0.1 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) ethanoic acid and \({\text{100 c}}{{\text{m}}^{\text{3}}}{\text{ 0.1 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) sodium ethanoate

II.     \({\text{100 c}}{{\text{m}}^{\text{3}}}{\text{ 0.1 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) ethanoic acid and \({\text{50 c}}{{\text{m}}^{\text{3}}}{\text{ 0.1 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) sodium hydroxide

III.     \({\text{100 c}}{{\text{m}}^{\text{3}}}{\text{ 0.1 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) ethanoic acid and \({\text{100 c}}{{\text{m}}^{\text{3}}}{\text{ 0.5 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) sodium hydroxide

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

A buffer solution is formed by mixing equal volumes of \({\text{1.00 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) propanoic acid and \({\text{0.500 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\) potassium propanoate.

What is the concentration, in \({\text{mol}}\,{\text{d}}{{\text{m}}^{ - 3}}\), of \({\text{[}}{{\text{H}}^ + }{\text{(aq)]}}\) in this buffer solution? (\({K_{\text{a}}}\) for propanoic acid is \(1.30 \times {10^{ - 5}}\).)

A.     \(2.60 \times {10^{ - 5}}\)

B.     \(1.95 \times {10^{ - 5}}\)

C.     \(1.30 \times {10^{ - 5}}\)

D.     \(0.650 \times {10^{ - 5}}\)

The \({\text{p}}{K_{\text{a}}}\) of ethanoic acid is 4.8 at 298 K. Which combination will produce a buffer solution with a pH of 4.8 at 298 K?

A.     \({\text{20.0 c}}{{\text{m}}^{\text{3}}}{\text{ of 1.0 mol}}\,{\text{d}}{{\text{m}}^{ - {\text{3}}}}{\text{ C}}{{\text{H}}_{\text{3}}}{\text{COOH and 10.0 c}}{{\text{m}}^{\text{3}}}{\text{ of 1.0 mol}}\,{\text{d}}{{\text{m}}^{ - {\text{3}}}}{\text{ NaOH}}\)

B.     \({\text{20.0 c}}{{\text{m}}^{\text{3}}}{\text{ of 1.0 mol}}\,{\text{d}}{{\text{m}}^{ - {\text{3}}}}{\text{ C}}{{\text{H}}_{\text{3}}}{\text{COOH and 20.0 c}}{{\text{m}}^{\text{3}}}{\text{ of 1.0 mol}}\,{\text{d}}{{\text{m}}^{ - {\text{3}}}}{\text{ NaOH}}\)

C.     \({\text{10.0 c}}{{\text{m}}^{\text{3}}}{\text{ of 1.0 mol}}\,{\text{d}}{{\text{m}}^{ - {\text{3}}}}{\text{ C}}{{\text{H}}_{\text{3}}}{\text{COOH and 20.0 c}}{{\text{m}}^{\text{3}}}{\text{ of 1.0 mol}}\,{\text{d}}{{\text{m}}^{ - {\text{3}}}}{\text{ NaOH}}\)

D.     \({\text{14.8 c}}{{\text{m}}^{\text{3}}}{\text{ of 1.0 mol}}\,{\text{d}}{{\text{m}}^{ - {\text{3}}}}{\text{ C}}{{\text{H}}_{\text{3}}}{\text{COOH and 10.0 c}}{{\text{m}}^{\text{3}}}{\text{ of 1.0 mol}}\,{\text{d}}{{\text{m}}^{ - {\text{3}}}}{\text{ NaOH}}\)

Which mixture will form a buffer in aqueous solution?

A.     \({\text{0.10 mol N}}{{\text{H}}_{\text{3}}} + {\text{0.20 mol HCl}}\)

B.     \({\text{0.10 mol N}}{{\text{H}}_{\text{3}}} + {\text{0.20 mol NaOH}}\)

C.     \({\text{0.10 mol NaOH}} + {\text{0.20 mol KCl}}\)

D.     \({\text{0.20 mol N}}{{\text{H}}_{\text{3}}} + {\text{0.10 mol HCl}}\)