Reactivity 3.1—Proton transfer reactions HL Flashcards
What describes the concentration of hydroxide ions in a solution?
The pOH scale, which is calculated as pOH = –log10[OH–]; where [OH–] = 10^(-pOH).
How are the strengths of weak acids and bases described?
By their dissociation constants (Ka for acids, Kb for bases) and their logarithmic expressions (pKa and pKb).
What is the relationship between Ka and Kb for a conjugate acid–base pair?
Ka × Kb = Kw, which can be derived from their expressions for Ka and Kb.
What determines the pH of a salt solution?
The relative strengths of the parent acid and base.
What characterizes pH curves of different combinations of strong and weak monoprotic acids and bases?
They have characteristic shapes and features, depending on the strengths of the acids and bases involved.
What are acid–base indicators?
Weak acids where the components of the conjugate acid–base pair have different colors. The pH of the endpoint, where it changes color, approximately corresponds to its pKa value.
How is an appropriate indicator for a titration chosen?
It should have an endpoint range that coincides with the pH at the equivalence point of the titration.
What is a buffer solution?
A solution that resists change in pH upon the addition of small amounts of acid or alkali.
What factors determine the pH of a buffer solution?
The pKa or pKb of its acid or base and the ratio of the concentration of acid or base to the concentration of the conjugate base or acid.
What is the significance of titration in quantitative analysis?
Titration is a widely used technique in quantitative analysis for determining the concentrations of acids and bases, utilized in industries like food, pharmaceutical, and cosmetics. It helps interpret the general shapes of pH curves for combinations of strong and weak acids and bases.
What is the significance of the half-equivalence point in a titration curve?
At the half-equivalence point, the solution acts as a buffer with equal amounts of the weak acid and its conjugate base, resisting changes in pH. The pH at this point equals the pKa of the acid.
What are the characteristics of a pH curve for a weak base-weak acid titration?
Starts at the weak base’s pH, decreases to the weak acid’s pH, with the equivalence point at pH 7 due to a neutral salt. This curve shows a very small change in pH, making the equivalence point hard to determine.
