A biochemistry lab uses 50.0 mL of a phosphate buffer that is 0.50 M in both H₂PO₄⁻…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A biochemistry lab uses 50.0 mL of a phosphate buffer that is 0.50 M in both H₂PO₄⁻ and HPO₄²⁻ (pKₐ₂ = 7.21).
To the buffer, 1.00 mL of 0.10 M NaOH is accidentally introduced.
(1) Calculate the new pH of the solution after the NaOH addition, showing all steps and using appropriate significant figures.
(2) State whether the pH change represents an increase, decrease, or negligible drift relative to the initial pH, and quantify the magnitude of the drift.
(3) Many laboratory protocols consider a buffer to be effective if added reagents cause less than a ±0.10 pH-unit change. Determine whether this buffer remained effective after the NaOH addition and briefly justify your conclusion.