A chemist titrates a 50.0 mL sample of 0.100 M hydrochloric acid with 0.100 M sodium…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A chemist titrates a 50.0 mL sample of 0.100 M hydrochloric acid with 0.100 M sodium hydroxide at 25 °C. A selection of acid–base indicators is provided.
Indicator
pKa
Color-change interval (pH)
Methyl orange
3.7
3.1 – 4.4
Bromothymol blue
7.1
6.0 – 7.6
Phenolphthalein
9.3
8.2 – 10.0
(a) Calculate the volume of NaOH required to reach the equivalence point.
(b) Determine and justify the expected pH at the equivalence point of this titration.
(c) Using the data provided, identify every indicator that would allow an accurate visual detection of the endpoint for this titration and justify each choice.
(d) Explain why the accuracy of endpoint detection is generally less sensitive to indicator choice in this titration than in titrations involving weak acids or weak bases.