Answer:
The percent by mass of benzoic acid = 89.7 %
Explanation:
Step 1: Data given
Molarity of NaOH = 0.2099 M
Mass of the sample = 1.021 grams
Volume of NaOH = 35.73 mL = 0.03573 L
Step 2: The balanced equation
C6H5COOH(aq) + NaOH(aq) → NaC6H5COO(aq) + H2O(l)
Step 3: Calculate moles NaOH
Moles NaOH = molarity NaOH * volume NaOH
Moles NaOH = 0.2099 * 0.03573 L
Moles NaOH = 0.00750 moles
Step 3: Calculate moles benzoic acid
From your balanced equation - benzoic acid reacts in 1:1 molar ratio with NaOH
The sample must have contained 0.00750 moles benzoic acid
Mass benzoic acid in 0.00750 moles = 0.00750 * 122.12 = 0.9159 g benzoic acid
Mass % acid in sample = 0.9159/1.021 * 100 = 89.7% purity.
The percent by mass of benzoic acid = 89.7 %
