What is the molarity of OH- in a 7.83×10-3 M NaClO solution that hydrolyzes according to the equation.
ClO-(aq) + H2O(l) = OH-(aq) + HClO(aq)
The information they give is that constants Kh=2.86E-7
I know how to solve the problem when the constant Kw is involved (1E-14) i tried using those steps but they don't work with Kh..
Oh but they do IF you handle Kh right. The hydrolysis constant = Kh = Kb = (Kw/Ka) or in the case of acids, Kh = Ka = (Kw/Kb). Said another way, the hydrolysis constant, Kh, for ClO^- is just Kb for ClO^-. What the author of the problem has done is s/he has already divided Kw/Ka and given you the answer of 2.86E-7 = Kh. Look in you text for Ka for HClO. My old book gives 3.5E-8 so
Kw/Ka = 1E-14/3.5E-8 = 2.857E-7 which rounds to 2.86E-7. Voila.
To find the molarity of OH- in the solution, we need to determine the concentration of OH- ions resulting from the hydrolysis of NaClO. In this case, the hydrolysis equation is:
ClO-(aq) + H2O(l) → OH-(aq) + HClO(aq)
First, we need to write the expression for the hydrolysis constant (Kh) for this reaction. The hydrolysis constant is defined as the product of the concentration of the hydroxide ion (OH-) and the concentration of the conjugate acid (HClO), divided by the concentration of the initial reactant (ClO-):
Kh = [OH-][HClO] / [ClO-]
We are given the value of Kh as 2.86 × 10^-7. Since we know the initial concentration of NaClO as 7.83 × 10^-3 M, we can substitute these values into the equation:
2.86 × 10^-7 = [OH-][HClO] / (7.83 × 10^-3)
Next, we have to determine the concentration of either OH- or HClO in terms of the other. We can simplify the equation by setting the concentration of HClO as x and the concentration of OH- as y:
2.86 × 10^-7 = y * x / (7.83 × 10^-3)
To get the concentration of OH-, we solve the equation by isolating y:
y = (2.86 × 10^-7) * (7.83 × 10^-3) / x
However, in order to determine the concentration of OH-, we need to know the concentration of HClO, which is not given in the problem. Therefore, without the value of either y or x, we cannot directly calculate the molarity of OH- in the solution.
Hence, the given information is not sufficient to determine the molarity of OH-.