Question

*please do not do problem 18! just help eith problem 17! thank you :)

detailed work very helpful! please write clear and legible ?

17. An initially 2.2 M aqueous solution of a weak monoprotic acid has a total ion concentration of 1.24 x 10-M when equilibrium is established. What is the acid-ionization constant, Ka, of the weak acid? (assume initial concentration of the acid is 2 102 x K) a. 1.7 x 10- b. 1.5 x 10 c. 1.2 x 10-1 d. 3.5 x 10-2 e. 8.7 x 10-5 18. What is the equilibrium hydronium ion concentration of an initially 4.0 M solution of hypochlorous acid, HOCI, at 25 °C (K, = 3 x 10-8? a. 3.5 x 10-4 M b.2.2 x 10-7M c. 2.4 x 10-M d. 4.9 x 10-M e. 1.2 x 10-4 M

Answer 1

17)

Let HA be the acid.

It dissociates into H+ and A-

HA dissociates as:

HA -----> H+ + A-

2.2 0 0

2.2-x x x

Since total ionic concentration is 1.24*10^-2 M and concentration of H+ and A- would be equal, we can say that

[H+] = [A-] = 1.24*10^-2 / 2 = 6.2*10^-3 M

So,

x = 0.062 M

Use:

Ka = [H+] [A-]/[HA]

= x*x / (2.2-x)

= (6.2*10^-3 * 6.2*10^-3) / (2.2 - 6.2*10^-3)

= 1.7*10^-5

Answer: a