How do I identify this acid?

Question

A 0.010M acid solution has a pH of 2.00. The acid could be

 

A. HNO3

B. H2SO4

C. HCOOH

D. CH3OOH

Answer 1

Arturo's comment's are correct but since the concentration of 0.01 M is given in the question, this will rule out a weak acid as having a pH of 2.00.  Also, choice D should be CH3COOH, not CH3OOH.

 

At 0.01 M, to have a pH of 2.00 it would have to be a strong monoprotic acid, since pH = -log [H⁺].

At 0.010 M, neither formic acid (HCOOH choice C) nor acetic acid (CH3COOH choice D) would have a pH of 2.00 as they are weak acids.  That leaves choice A (nitric acid) which is a strong monoprotic acid and choice B (sulfuric acid) which is a strong diprotic acid.  Sulfuric acid at 0.01 M will have a pH less than 2.00 since there are 2 hydrogens that can be donated.  Thus, the answer should be (A) HNO3.