AB EQI Practical

Question 1

The direct titration of a saturated solution of calcium hydroxide with standard hydrochloric acid often yields unreliable results. Explain why this is so.

Answer 1

Ca(OH)2 is a sparingly soluble solid, and the conc of OH- ions in the solution is too low, resulting in a low titre and hence percentage of error is too high

Question 2

Without any further calculations, explain why, if mass m was 0.20 g, Experiment II would be unsuccessful

Answer 2

the value of m is too small for there to be any observable change in pH after each addition of sodium ethanoate
the mass of m is too small to be measured precisely / accurately with a weighing balance especially since it needs to be divided into 5 equal amounts

Question 3

suggest a safety precaution

Answer 3

students should wear gloves when handling the 2.0moldm3 ethanoic acid as it is irritant / toxic
students should wear a mask as ethanoic acid is volatile