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Quantitative Analysis · Part 1 of 3
6 exam-style questions with model answers, plus 8 quick multi-choice questions — every question on this part of the standard, grouped by the 2 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
State the two relationships that must be used in this investigation, define each symbol with its unit, and state what each relationship is used for.
A student plans to determine the concentration of hydrochloric acid in a descaling product by titrating it against sodium hydroxide solution. Explain why this plan does not meet all the requirements of the standard, and describe a change that would fix it.
Two students investigate the concentration of ethanoic acid in vinegar. Student A titrates the vinegar directly. Student B dilutes the vinegar tenfold first. Both obtain the same final answer. Evaluate which investigation is the better piece of work for this standard, and justify your judgement.
Describe two problems a consumer product might present that would require the sample to be modified before titration, and state the modification for each.
Explain why a back titration is used to find the amount of calcium carbonate in an antacid tablet, rather than titrating the tablet directly with acid.
A student determining the ethanoic acid content of a dark balsamic vinegar dilutes the sample 20-fold so the phenolphthalein endpoint is visible. Justify how this modification affects the validity and the accuracy of the investigation, and evaluate one drawback.