A 0.23 M solution of a weak acid has a pH of 2.89. What is the Ka(acid ionization constant)for this acid?
HA ==> H^+ + A^-
Ka = (H^+)(A^-)/(HA)
Convert pH to H^+, substitute that for H^+ and A^- in the equation for Ka. For HA, substitute 0.23-H^+ and solve for Ka.
How do I convert pH to H^+?
To find the Ka (acid ionization constant) for a weak acid, you need to use the given concentration and pH of the solution. The Ka value represents the extent to which an acid dissociates into its ions in water.
Step 1: Convert the pH to [H₃O⁺] concentration.
pH is defined as the negative logarithm of the hydrogen ion concentration ([H₃O⁺]). The formula to find the [H₃O⁺] concentration is:
[H₃O⁺] = 10^(-pH)
In this case, [H₃O⁺] = 10^(-2.89)
Step 2: Calculate the initial concentration of the weak acid using the formula:
[H₃O⁺] = [A⁻] = [HA]initial
Step 3: Calculate the equilibrium concentration of the weak acid.
[H₃O⁺] = [A⁻] + [HA]
Since [H₃O⁺] = [A⁻] = [HA]initial, the equilibrium concentration of the weak acid is (0.23 - [HA]initial).
Step 4: Substitute the concentrations into the Ka expression.
Ka = ([A⁻] * [H₃O⁺]) / [HA]
Substituting the concentrations, we get:
Ka = [(0.23 - [HA]initial) * (10^(-2.89))] / [HA]
Without the value for [HA]initial, we cannot calculate the exact value of Ka. However, we can still provide you with the equation to calculate it.