Chemistry – Experimental techniques and chemical analysis - Acid-base titrations | e-Consult

a) Average volume of titrant used = (25.15 + 25.00 + 25.05) / 3 = 25.05 cm³

b) The concentration of the weak acid can be calculated using the following equation:

Concentration of weak acid (mol/dm³) = (Average volume of titrant used (dm³) x Concentration of the strong acid (mol/dm³)) / Volume of weak acid solution (dm³)

Assuming the strong acid is 0.1 mol/dm³ and the volume of weak acid solution is 0.02 dm³:

Concentration of weak acid = (0.025 dm³ x 0.1 mol/dm³) / 0.02 dm³ = 0.125 mol/dm³

c) The significance of using a weak indicator is that it changes colour over a wider pH range than a strong indicator. This is important for titrations involving weak acids because the pH changes gradually near the equivalence point. A weak indicator provides a more gradual colour change, making it easier to determine the endpoint accurately.