This question is about weak acids and buffer solutions.
Propanoic acid, CH3CH2COOH\text{CH}_3\text{CH}_2\text{COOH}CH3CH2COOH, is a weak monobasic acid.
Explain what is meant by the term weak monobasic acid.
A buffer solution is prepared by dissolving 1.60 g1.60\text{ g}1.60 g of sodium hydroxide, NaOH\text{NaOH}NaOH, in 500.0 cm3500.0\text{ cm}^3500.0 cm3 of 0.200 mol dm−30.200\text{ mol dm}^{-3}0.200 mol dm−3 propanoic acid.
This buffer solution has a pH of 4.704.704.70 at 25∘C25^\circ\text{C}25∘C.
Calculate the acid dissociation constant, KaK_aKa, of propanoic acid at 25∘C25^\circ\text{C}25∘C.
Assume that the volume of the solution remains constant at 500.0 cm3500.0\text{ cm}^3500.0 cm3 when the sodium hydroxide is dissolved. Give your answer to 3 significant figures.
Ka=K_a = Ka= ........................................ mol dm−3\text{mol dm}^{-3}mol dm−3
When a small volume of water is added to this buffer solution, the pH does not change.
Explain why the pH does not change.
