Solve Ka: Percent Ionization of Formic Acid - 2.85%

[George3]

Homework Statement

What concentration of formic acid would give an aqueous solution in which 2.85 percent of the formic acid molecules are ionized? Assume that Ka for formic acid is 1.80E-4 .

Homework Equations

The Attempt at a Solution

X^2 / .0285 - X = 1.8E-4
X = .00226
M = .0285 - .00226 = .0262M
This is wrong. Any ideas?

 

[chemisttree]

Let X be the concentration of formic acid before dissociation. 0.0285X represents what?

Can you get there from here?