1) The concentration of a propanoic acid, C₂H₅COOH, solution was determined by titration with standardised 0.100 M sodium hydroxide, NaOH, solution at 25 °C. The reaction for this titration is shown below

A 0.10 M solution of sodium propanoate, C₂H₅COONa, in water has a pH of 8.9 at 25 °C. The most appropriate indicator to use for this titration would be
A. thymol blue.
B. methyl red.
C. phenol red.
D. bromothymol blue.

Solution

2) Before water treatment authorities release water into the environment, the water is tested to ensure it is safe and meets environmental standards. The concentration of organic carbon is one indicator of water quality. In an experiment, a student determines the concentration of organic carbon by conducting a redox titration between the organic carbon in a water sample and standard acidifi ed potassium permanganate solution, KMnO₄. To accurately determine the concentration of organic carbon, an action the student should take is to
A. collect samples before and after a storm.
B. repeat the titration using a different standard solution.
C. use a measuring cylinder to measure the volumes of water samples.
D. rinse the burette with deionised water before fi lling it with the standard acidified KMnO₄ solution.

Solution