The mass percent of benzoic acid in the sample is 55.5%.
The equation of the reaction is; HC7H5O2(aq) + NaOH(aq) ----> NaC7H5O2(aq) + H2O(l)
Number of moles of NaOH reacted = concentration × volume
Number of moles of NaOH reacted = 10.59/1000 L × 0.1546 M
Number of moles of NaOH reacted = 0.0016 moles of NaOH
Since the reaction is 1:1, 0.0016 moles of HC7H5O2 reacted also.
Hence, mass of HC7H5O2 = 0.0016 moles × 122 g/mol = 0.1952 g
Mass percent of HC7H5O2 in the original sample = 0.1952 g/ 0.3518 g × 100 = 55.5%
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