Question

This is probably easier then my making it but...
Calculate the ph of a forming acid solution that contains 1.35% forming acid by mass. Assume a density of 1.01g/ml for the solution.

Answer 1

1.35% formic acid w/w means 1.35 g formic acid/100 g soln. 1.35g/molar mass = moles.
Use density to convert 100 g soln to volume, then mols formic acid/L soln = M formic acid.
Now go through the ICE chart and Ka and solve for pH. Is this enough to get you started?

Answer 2

I think I made a mistake....
1.35g/100g solution=0.0135grams
0.0135g/1.01g=0.01337ml
Then...
1.35g/46.03g CH2O2= 0.0293mols

Then...
0.0293mol/ 1.337X10^-5 = 2.19X10^3 M

pH= -log[H+]
PH=-log(2.19X10^3)
But I get a negative ph.

Answer 3

I think more than one. :-).
1.35 g/100g = 0.02933/100 g soln
mass = v x density
volume = m/d = 100/1.01 = 99 mL or 0.099 L
So the M of the soln is 0.02933/0.099 = 0.296 M.
You didn't set up an ICE chart. I am letting HX stand for formic acid.
.........HX ==> H^+ + X^-
initial..0.296...0......0
change...-y.......y.....y
equil...0.296-y...y.....y

Ka = (H^+)(X^-)/(HX)
LOOK UP Ka and substitute from the ICE chart above, solve for (H^+) then convert to pH. I would think the pH should be about 2 or so but I don't remember Ka for formic acid.