what mass of formic acid must be dissolved in 250 ml of deionized water to produce a solution of pH 1.83?[ka of HCOOH=1.77*10^-4, Mw=46]
To determine the mass of formic acid needed to produce a solution of pH 1.83, you'll need to use the equation for the dissociation of formic acid:
HCOOH ⇌ H+ + HCOO-
First, calculate the concentration of H+ ions in the solution using the pH value:
pH = -log[H+]
Rearranging the equation, we get:
[H+] = 10^(-pH)
Substituting the pH value of 1.83:
[H+] = 10^(-1.83)
Next, we'll use the Ka value of formic acid to determine the concentration of formic acid in the solution:
Ka = [H+][HCOO-] / [HCOOH]
Since the concentration of H+ equals the concentration of HCOO-, the equation becomes:
Ka = [H+]^2 / [HCOOH]
Rearranging the equation, we can solve for [HCOOH]:
[HCOOH] = [H+]^2 / Ka
Now, let's plug in the given values:
[HCOOH] = (10^(-1.83))^2 / (1.77 x 10^(-4))
Simplifying this expression will give you the concentration of formic acid. Finally, you can convert this concentration to mass by using the molecular weight (Mw) and the volume of the solution:
Mass = Concentration (mol/L) x Volume (L) x Mw (g/mol)
Remember to convert 250 mL to L before using the above formula.
[H3O+] = 10^-2.85 = 0.00141 M = [C6H5COO-]
6.3 x 10^-5 = (0.00141)^2 / x
x = 0.032 M
Moles = 0.032 x 0.350 L = 0.011
Mass = 0.011 mol x 122 g/mol = 1.34 g