Calculate the pH of the solution made by dissolving 8.00 g of lactic acid.
You can't work this problem unless you are told the volume.
For simplicity, call lactic acid, HL.
HL ==> H^+ + L^-
Ka = (H^+)(L^-)/((HL)
Set up an ICE chart and solve for (H^+), then convert to pH.
You will need the molarity of the HL and that will be moles/L. moles = grams/molar mass.