Calculate to 2 decimal places the concentration of the conjugate acid and conjugate base for a total buffer concentration of 250 mM at pH 12. Show all details of your working out; in each step of your working out use the chemical formulas of the compounds that constitute the weak acid and conjugate base. Show all units and state the final answer in a complete sentence. H2PO4- is the weak acid and HPO42- is the conjugate base
Question
Calculate to 2 decimal places the concentration of the conjugate acid and conjugate base for a total buffer concentration of 250 mM at pH 12. Show all details of your working out; in each step of your working out use the chemical formulas of the compounds that constitute the weak acid and conjugate base. Show all units and state the final answer in a complete sentence. H2PO4- is the weak acid and HPO42- is the conjugate base
Solution
To calculate the concentration of the conjugate acid (H2PO4-) and the conjugate base (HPO42-) in a buffer solution, we can use the Henderson-Hasselbalch equation:
pH = pKa + log ([A-]/[HA])
where:
- pH is the pH of the solution
- pKa is the acid dissociation constant
- [A-] is the concentration of the base
- [HA] is the concentration of the acid
Given that the pH is 12 and the pKa of H2PO4- is 7.2, we can rearrange the equation to solve for the ratio of base to acid:
12 = 7.2 + log ([HPO42-]/[H2PO4-])
Subtract 7.2 from both sides:
4.8 = log ([HPO42-]/[H2PO4-])
To remove the log, we use the inverse operation, which is 10 raised to the power of the number. So:
10^4.8 = [HPO42-]/[H2PO4-]
This gives us the ratio of base to acid.
The total buffer concentration is given as 250 mM, which is the sum of the acid and base concentrations. We can express this as:
[HPO42-] + [H2PO4-] = 250 mM
We can then express [H2PO4-] in terms of [HPO42-] using the ratio we calculated earlier:
[HPO42-] + [HPO42-]/(10^4.8) = 250 mM
Solving this equation will give us the concentration of the base, [HPO42-]. Once we have this, we can find the concentration of the acid, [H2PO4-], by subtracting the base concentration from the total buffer concentration.
After solving, we find that the concentration of the conjugate base, HPO42-, is approximately 249.96 mM and the concentration of the conjugate acid, H2PO4-, is approximately 0.04 mM.
So, in a buffer solution with a total concentration of 250 mM at pH 12, the concentration of the conjugate base, HPO42-, is 249.96 mM and the concentration of the conjugate acid, H2PO4-, is 0.04 mM.
Similar Questions
Calculate to 2 decimal places, the ratio of base/acid at pH 12. Show all details of your working out. In each step of your working out use the chemical formulas of the compounds that constitute the weak acid and conjugate base. State the final answer in a complete sentence. H2PO4- is the weak acid and HPO42- is the conjugate base.
This question concerns part 1 of this lab.You need to make a buffer solution by mixing both a weak acid and its conjugate base in the right proportions to achieve the desired pH.Your desired target pH is 5.40. You have been provided with 5.00 mL of 0.100 M acetic acid solution.How many moles of sodium acetate do you need to add to this solution to obtain a buffer solution at the desired pH? The pKa of acetic acid is 4.74. Answer
The Henderson-Hasselbalch equation can be used to calculate Question 4 options: the pKa of a weak acid. the amount of salt and acid to add to form a specific buffer. the pH of a solution of an organic acid. All of the above A and C only
Fill in the missing chemical formulae in the tables below.acid conjugate base base conjugate acidNH+4 NH3 HCO−3 H2CO3H2PO−4 HPO42− CO2−3 HCOH3O+ H2O H2O
The conjugate acid of PO43- is:Question 2Select one:a.PO43-b.H3PO3c.H2PO4-d.HPO42-e.H2PO42-
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.