Calculate the pH of a 1.14 mol.L–1 solution of hydrofluoric acid. The pKa of HF is 3.17.Enter your answer to 2 decimal places.

To calculate the pH of a solution of a weak acid like hydrofluoric acid (HF), we can use the formula for the ionization of a weak acid and the definition of pH.

Step 1: Write the ionization equation for the weak acid. HF ⇌ H+ + F-

Step 2: Write the expression for the acid dissociation constant (Ka). Ka = [H+][F-]/[HF]

Step 3: Use the pKa to find the Ka. pKa = -log(Ka) So, Ka = 10^-pKa = 10^-3.17 = 0.000677

Step 4: Set up an ICE (Initial, Change, Equilibrium) table to find the equilibrium concentrations.

Initial: [HF] = 1.14 M, [H+] = 0, [F-] = 0

Change: [HF] = -x, [H+] = +x, [F-] = +x

Equilibrium: [HF] = 1.14 - x, [H+] = x, [F-] = x

Step 5: Substitute the equilibrium concentrations into the Ka expression and solve for x ([H+]).

0.000677 = x*x/(1.14 - x)

Assuming x is much smaller than 1.14 (since HF is a weak acid and does not ionize completely), the equation simplifies to:

0.000677 = x^2/1.14

Solving for x gives x = sqrt(0.000677 * 1.14) = 0.0279

Step 6: Calculate the pH. pH = -log[H+] = -log(0.0279) = 1.55

So, the pH of a 1.14 mol.L–1 solution of hydrofluoric acid is approximately 1.55.