Hz is a weak acid. an aqueous solution of hz is prepared by dissolving 0.020 mol of hz in sufficient water to yield 1.0 l of solution. the ph of the solution was 4.93 at 25.0 °c. the ka of hz is hz is a weak acid. an aqueous solution of hz is prepared by dissolving 0.020 mol of hz in sufficient water to yield 1.0 l of solution. the ph of the solution was 4.93 at 25.0 °c. the ka of hz is 1.4 ⋅ 10-10 1.2 ⋅ 10-5 2.8 ⋅ 10-12 9.9 ⋅ 10-2 6.9 ⋅ 10-9

From the information presented in the question, the Ka of the solution is 6.9 × 10^-9.

Concentration of HZ = 0.020 mol/1L = 0.020 M

          HZ(aq) + H2O(l) ⇄ H3O^+(aq) +   Z^-(aq)

I          0.020                       0                   0  

C        -x                               +x                 +x

E      0.020 - x                     x                   x

Ka = [ H3O^+] [Z^-]/[HZ]

Ka = x^2/ 0.020 - x

Hence,  [ H3O^+] = Antilog (-4.93) = 1.17 × 10^-5 M

Also;  [ H3O^+] = [Z^-] = x

Substituting values;

Ka = (1.17 × 10^-5)^2/ 0.020 - 1.17 × 10^-5

Ka = 6.9 × 10^-9

Hence, the Ka of the solution is 6.9 × 10^-9.

Learn more about pH: link