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Quantitative Investigation · 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.
Explain why the purpose "to find out which brand of orange juice contains the most vitamin C" does not meet this standard, and rewrite it so that it does.
Explain why a 1 : 1 acid–base titration is not suitable for this standard, and describe two alternatives that would be.
A student proposes to investigate how the ascorbic acid content of kiwifruit changes during ripening, using five fruit picked on five different days. Evaluate this design and justify the improvements you would make.
Explain what a primary standard is, state the properties one must have, and give two examples of redox titrants that are NOT primary standards.
Explain why warming is required when standardising permanganate against sodium oxalate, and explain how this relates to the reaction occurring.
A student investigating how ascorbic acid content changes over ten days analyses one sample per day, using the same bottle of iodine solution throughout and standardising it only on day one. Their results show a steady decline. Justify why this conclusion cannot be trusted, and evaluate what would be needed to secure it.