if 0.24o moles of a monoprotic weak acid is titrated with NaOH, what is the PH of the solution at the 1/2 equivalence point.
It's pKa whatever that is. Do you have a Ka for HA?
To determine the pH of the solution at the 1/2 equivalence point, we need to consider the dissociation of the weak acid and the subsequent reaction with NaOH.
First, we need to find the initial concentration of the weak acid. Given that we have 0.24 moles of the weak acid and that it is monoprotic (meaning it donates only one proton), we can assume that the initial concentration of the acid (HA) is the same as the moles:
Initial concentration (HA) = 0.24 M
At the 1/2 equivalence point, half of the initial moles of the weak acid have reacted with NaOH. Therefore, we have 0.12 moles of the weak acid remaining.
Now, let's consider the dissociation of the weak acid (HA). It can be represented as follows:
HA(aq) ⇌ H+(aq) + A-(aq)
This dissociation reaction can be expressed by the acid dissociation constant, Ka, which relates the concentrations of the products and reactants:
Ka = [H+][A-] / [HA]
Since the weak acid is monoprotic, the concentration of H+ is equal to the concentration of HA that dissolves, while the concentration of A- is equal to the concentration of HA that dissociates.
At the 1/2 equivalence point, [HA] = 0.12 M (concentration of remaining weak acid). However, since exactly half of the weak acid has dissociated, we also have [H+] = [A-] = 0.12 M.
Now, we can substitute these concentrations into the equation for Ka:
Ka = (0.12)(0.12) / (0.12) = 0.12
The value of Ka can be used to find the concentration of H+ ions at the 1/2 equivalence point. We can use the equation for Ka to calculate the concentration of H+:
Ka = [H+]^2 / [HA]
0.12 = [H+]^2 / 0.12
[H+]^2 = 0.12 * 0.12
[H+]^2 = 0.0144
[H+] = √0.0144
[H+] ≈ 0.12 M
Since the concentration of H+ ions is the same as the concentration of the remaining weak acid at the 1/2 equivalence point, the pH of the solution can be determined using the formula:
pH = -log[H+]
pH = -log(0.12)
pH ≈ 0.92
Therefore, at the 1/2 equivalence point, the pH of the solution is approximately 0.92.