A student uses 16.60 mL of 0.100 M NaOH to titrate a 0.2000-g sample of an unknown acid. Which of the following acids is the unknown most likely to be? Assume that only the hydrogens bonded to oxygen are titrated by the sodium hydroxide and that, because of experimental error, the student's value may not be identical to the theoretical value. A) oxalic acid, HOOCCOOH, molar mass 90 B) succinic acid, HOOCCH₂CH₂COOH, molar mass 118 C) benzoic acid, C₆H₅COOH, molar mass 122 D) phthalic acid, C₆H₄ (COOH)₂, molar mass 166 E) not enough information

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Quizplus · Accepted Answer

To find the unknown acid, we need to calculate the number of moles of acid in the given sample. Number of moles of NaOH = (16.60 mL) x (0.100 mol/L) = 0.00166 mol Since NaOH and the unknown acid react in a 1:1 ratio, the number of moles of acid must also be 0.00166 mol. Now we can calculate the molar mass of the acid by dividing the mass of the sample by the number of moles: Molar mass = (0.2000 g) / (0.00166 mol) = 120.5 g/mol Now we can compare this molar mass to the molar masses of the given acids: A) HOOCCOOH, molar mass 90 B) HOOCCH₂CH₂COOH, molar mass 118 C) C₆H₅COOH, molar mass 122 D) C₆H₄ (COOH)₂, molar mass 166 The best choice is C, benzoic acid, with a molar mass closest to the calculated molar mass of the unknown.

A Student Uses 16