Question

An environmental chemist analyzed the effluent (the released waste materials) from an industry process known to produce the compound carbon tertrachloride (CCI⁴) and benzoyl acid (C⁶H⁵COOH) a weak acid that has one acidic hydrogen atom per molecule. A sample of this effluent having a mass of 0.3518 g was shaken with water and the resultant aqueous solution required 10.59 mL of 0.1546 M NaOH for neutralization. Calculate the mass of percent of C⁶H⁵COOH in the original sample

Answer 1

The mass percent of benzoic acid in the sample is 55.5%.
So the equation 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%