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chem as level

The student adds a lump of limestone with mass 0.13 g to 25.00 cm3 of 0.100 mol dm–3 hydrochloric
acid and stirs until the reaction is finished. The solution is then filtered.
The excess acid in the filtered solution reacts with 7.00 cm3
of 0.100 mol dm–3 sodium hydroxide.
The equations for the reactions are:
CaCO3 + 2HCl → CaCl2 + CO2 + H2O
HCl + NaOH → NaCl + H2O
now the question is The student realises that the percentage of calcium carbonate should be given to two significant
figures.
Suggest how the student might vary the method, using the same apparatus, to get a result that could
be accurately reported to three significant figures
can someone explain this to me