The pH of an aqueous solution of 0.100 M HIO is 9.64.
Let's calculate the pH of an aqueous solution of 0.100 M HIO, given that the Ka of HIO is 2.3×10-11.
We can use the following equation to calculate the pH of a weak acid solution:
pH = pKa + log([A-]/[HA])
where:
pKa is the negative logarithm of the acid dissociation constant (Ka)
[A-] is the concentration of the conjugate base (IO-)
[HA] is the concentration of the acid (HIO)
We can assume that the concentration of IO- is equal to the concentration of HIO, since the acid is only partially dissociated.
Therefore, we can simplify the equation to:
pH = pKa + log([HIO])
We can now plug in the values we know:
pKa = -log(2.3×10-11) = 10.64
[HIO] = 0.100 M
pH = 10.64 + log(0.100) = 9.64
Therefore, the pH of an aqueous solution of 0.100 M HIO is 9.64.
Question
We can observe the common-ion effect in action by comparing how much a pure sample of acid dissociates to how much a sample of an acid dissociates when its conjugate base is in solution. Let's consider the oxoacid HIO, which has a Ka of 2.3×10-11.
1) Calculate the pH of an aqueous solution of 0.100 M HIO. (Due to the low Ka value, you may apply the 5% approximation to avoid the quadratic equation if you wish.)