A laboratory protocol calls for successive additions of titrant to a buffer that…
CHEMISTRY · Single correct · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A laboratory protocol calls for successive additions of titrant to a buffer that initially contains 0.050 mol HA and 0.075 mol A⁻ in a total volume of 0.50 L.
• Step 1: 10.0 mL of 0.500 M HCl is added.
• Step 2: 10.0 mL of 0.500 M NaOH is added to the same flask after thorough mixing.
Assuming negligible volume change for each addition, which graph best describes the qualitative trend of pH versus volume of titrant added?
(a) No significant change in pH during either step because the buffer is equally resistant to both acid and base.
(b) An initial small decrease in pH during Step 1 followed by a larger rise past the original pH during Step 2.
(c) A sharp decrease in pH during Step 1 followed by a return exactly to the original pH during Step 2.
(d) A small decrease in pH during Step 1 followed by a small rise that ends slightly below the original pH after Step 2.