Question

Part A A 0.150 M weak acid solution has a pH of 2.97. Find Ka for the acid.

Part B Find the percent ionization of a 0.195 M  HC2H3O2 solution. (The value of Ka for HC2H3O2 is 1.8×10−5.)

Part C Find the pH of a 0.0191 M solution of hypochlorous acid. (The value of Ka for hypochlorous acid is 2.9×10−8.)

Part D Find the pH of a 0.014 M solution of HF. (The value of Ka for HF is 3.5×10−4.)

Part E Find the [H3O+] concentration of a 0.281 M  acetic acid solution. (The value of Ka for acetic acid is 1.8×10−5.)

Answer 1

Part A

K_a = ( [H⁺] [A¯] ) / [HA]

We know [H⁺] = 10¯^pH

Thus, [H⁺] = 10¯^2.97 =0.00107 M

[A¯] = 0.00107 M (1:1 ration between  [H⁺] and [A¯] )

K_a = [(0.00107) (0.00107)] / 0.150

Thus, K_a=7.63 x 10¯⁶