Question

The ionization constant for the hypothetical weak acid, HA, is 1.0 × 10−5. What is the equilibrium concentration of [H3O+] in 0.20 M HA solution?

a. 4.3 × 10−3 M
b. 8.1 × 10−4 M
c. 1.4 × 10−3 M
d. 1.0 × 10−5 M
e. 5.0 × 10−4 M

Answer 1

The correct answer is d.) The equilibrium concentration of [H3O+] in a 0.20 M HA solution with a Ka value of 1.0 × 10^-5 is 1.0 × 10^-5 M.

Step-by-step explanation:

To find the equilibrium concentration of [H3O+] in a 0.20 M HA solution, we can use the ionization constant (Ka) of the weak acid. The ionization constant is given as 1.0 × 10^-5.

Using an ICE table, we can set up the equation:

HA ⇌ H+ + A-

Initial: [HA] = 0.20 M, [H+] = 0 M, [A-] = 0 M

Change: -x, +x, +x

Equilibrium: [HA] = 0.20 - x, [H+] = x, [A-] = x

Since the equilibrium concentration of [H3O+] is equal to x, we can substitute x into the equation for [H3O+] and solve for x:

[H3O+] = x = 1.0 × 10^-5

Therefore, the equilibrium concentration of [H3O+] in the 0.20 M HA solution is 1.0 × 10^-5 M, which corresponds to option d.