Okay so my lecturer has this in our slides and there are no notes just a heading saying speaciation, I have tried google and everything I have read does not include pH in their question. Please help me
Calculate the equilibrium concentrations of the different species in a 0.100 M fumaric acid solution at pH 2.00.For fumaric acid, pKa1 = 3.053 and pKa2 = 4.494
I would start of with:
Ka= antilog(pka)
H2M ----- 2H+ + M-
HM- ----- H+ + M-
Then: Ka1 = [H][M]/H2M
Let H and M equal X and let H2M equal 0.1-×
Ka2 = [H][M]/HM
Am I suppose to use the pH as the H+ species
Like [H+] = antilog [pH]
Help please!
http://www.speciation.net/Public/Document/2003/09/11/495.html
Yes, use pH as the H+ species. Yes, like that.
Then if H+ equals antilog pH, M- would also be equal to H+ , so then what will I be solving for? Because H2M species is given
Sorry if this is a stupid question, I really don't know
Thanks you!!
To calculate the equilibrium concentrations of the different species in a fumaric acid solution at pH 2.00, you can follow these steps:
1. Start by calculating the concentration of H+ ions based on the given pH value.
- Since pH is defined as the negative logarithm of the H+ concentration, you can calculate it using the formula [H+] = 10^(-pH). In this case, [H+] = 10^(-2.00).
2. Next, use the given pKa values to calculate the equilibrium constants (Ka) for the acidic dissociation reactions.
- Ka1 = 10^(-pKa1)
- Ka2 = 10^(-pKa2)
3. Now, assign variables for the equilibrium concentrations of the species:
- Let [H2M] be x (initially 0.100 M - x, as you mentioned).
- Let [HM-] be y.
- Let [M-] be z.
4. Construct the equilibrium expressions using the definitions of the equilibrium constants:
- Ka1 = (y * x) / (0.100 - x)
- Ka2 = (z * y) / x
5. Substitute the values obtained in steps 1, 2, and the given initial concentration in step 3 into the equilibrium expressions.
6. Solve the resulting system of equations to find the equilibrium concentrations of [H2M], [HM-], and [M-].
It's important to note that these calculations require solving a quadratic equation, as the expressions obtained in step 4 will result in a quadratic equation. You can use various methods to solve the quadratic equation, such as factoring, completing the square, or using the quadratic formula. Once you solve the quadratic equation, you should obtain the equilibrium concentrations of the species in the fumaric acid solution at pH 2.00.