Question

Solution of formic acid (HCOOH) with a pH of 1.98. Find the molarity of the acid.

Answer 1

........HCOOH ==> H^+ + HCOO^-
I.........M.......0......0
C........-x.......x......x
E........M-x......x......x

The problem tells you the pH is 1.98. Use pH = -log(H^+) to find x. Then substitute into Ka expression for HCOOH (you will need to look up Ka for HCOOH) and solve for M.