Calculate the pH of .100M of HClO2.
HClO2 is a weak acid.
HClO2 + H2O ==> H3O^+ + ClO2^-
Ka = (H3O^+)(ClO2^-)/(HClO2)
Set up an ICE chart, calculate (H^+) and convert that to pH.
I keep getting 1.479, but the program I use for homework keeps counting it wrong. Am I totally off?
I don't know what value you used for Ka for HClO2. I looked on the net and found 0.012 in two places.
It would have been better if you showed your work, then I could find the trouble. I suspect you didn't solve the queadratic but I could be mistaken.
The equation should be
Ka = (x)(x)/(0.1-x) = 0.012 or whatever you used for Ka. Using my value for Ka, I found H^+ = 0.02916 which gives a pH of 1.53 something. To get 1.479 you must have a H^+ of 0.03319. But I can't compare our answers since we may have used totally different values for Ka. If that isn't the problem with your answer then the next best guess is that you are keying in too many or too few significant figures. That is often the problem with the data base answers.
To calculate the pH of a solution of HClO2, we need to know its dissociation constant (Ka) value. However, HClO2 is a weak acid, and its dissociation can be represented by the following equation:
HClO2 ⇌ H+ + ClO2
The Ka expression for this dissociation can be written as:
Ka = [H+][ClO2] / [HClO2]
At equilibrium, we can assume that the concentrations of H+ and ClO2 are equal since HClO2 is the weak acid and ClO2 is the conjugate base. Let's denote this common concentration as "x".
Hence, the Ka expression becomes:
Ka = x * x / (0.100 - x)
Given that the initial concentration of HClO2 is 0.100 M, we can assume that the concentration of H+ at equilibrium will also be "x". So, the equilibrium expression for HClO2 can be written as:
Ka = x^2 / (0.100 - x)
Now, we can solve this equation to find the value of "x" using the quadratic formula:
x = [-b ± √(b^2 - 4ac)] / (2a)
Here, a = 1, b = 0, and c = -Ka * (0.100).
Using these values, we can substitute them into the quadratic formula and calculate the value of "x". Once we have the value of "x", we can calculate the pH using the equation:
pH = -log[H+]
This calculation provides the pH of the 0.100 M HClO2 solution.