Calculate the pH of a 1.18 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.

Step 5: Substitute the equilibrium concentrations into the Ka expression and solve for x, which represents [H+].

0.000677 = x^2/(1.18-x)

Assuming that x is much smaller than 1.18 (because HF is a weak acid and does not ionize completely), the equation simplifies to:

0.000677 = x^2/1.18

Solving for x gives x = sqrt(0.000677*1.18) = 0.030

Step 6: Calculate the pH. pH = -log[H+] = -log(0.030) = 1.52

So, the pH of the 1.18 mol/L solution of hydrofluoric acid is approximately 1.52.