Chemical Equilibria and pH Calculations

Flashcards to help review key concepts and calculations related to chemical equilibria and pH.

The pH of a 0.400 M CH₃COOH solution with a pKa of 4.74 is __.

4.84

In a solution of 0.0311 M HCN, the pKa is __.

9.21

For a buffer solution, the Henderson-Hasselbalch equation is __.

pH = pKa + log([A-]/[HA])

The relationship between Ka and Kb for a conjugate acid-base pair is __.

Kw = Ka * Kb

If the pKa of NH₃ is around 4.75, the pKb can be calculated as __.

9.25 (using pKw = 14 - pKa)

What is the pH of a buffer solution made of 0.25 M CH₃COOH and 0.25 M CH₃COONa?

The pH is 4.76 (using the Henderson-Hasselbalch equation, pKa = 4.76).

Calculate the pH of a buffer consisting of 0.10 M NH₃ and 0.15 M NH₄Cl.

The pH is approximately 9.25 (using the Henderson-Hasselbalch equation with pKa ≈ 9.25).

If you add 0.05 M HCl to 0.20 M acetic acid and 0.20 M sodium acetate, what happens to the pH of the buffer?

The pH will decrease slightly, but the buffer will resist a significant change due to its components.

What is the effect of dilution on the pH of a buffer solution containing 0.50 M H₂CO₃ and 0.50 M NaHCO₃?

Dilution will not significantly change the pH as long as the ratio of acid to base remains constant.

How much NaOH can be added to a buffer consisting of 0.30 M acetic acid and 0.30 M sodium acetate before the pH exceeds 5.00?

You can add a limited amount; calculate based on the ratio needed to maintain the desired pH using the Henderson-Hasselbalch equation.