you have 1.00 liter each of 0.10 M Na3PO4, Na2HPO4, NaH2po4 ka 1= 7.510^-3 ka2=6.210^-8 ka3=4.8*10^-13 a) prepare 500 ml of a buffer with PH= 7.6 b) how much 0.10 M HCL must be added to the 500ml of buffer to result in a PH=7.2 after the addition?

Question

you have 1.00 liter each of 0.10 M Na3PO4, Na2HPO4, NaH2po4 ka 1= 7.510^-3 ka2=6.210^-8 ka3=4.8*10^-13 a) prepare 500 ml of a buffer with PH= 7.6 b) how much 0.10 M HCL must be added to the 500ml of buffer to result in a PH=7.2 after the addition?

Answer 1

You want to use some of the NaH2PO4 as the acid and some of the Na2HPO4 as the base.

pH = pKa2 + log (250+x)*0.1/(250-x)*0.1
Solve for x and add to 250 to find mL of base to use and 250-x to find mL of acid to use. I would plug those numbers back into the Henderson-Hasselbalch equation and check that a pH of 7.60 is what you have prepared.

Answer 2

To prepare a buffer solution with a desired pH, we need to calculate the amounts of the conjugate acid and base needed. In this case, we have three components (Na3PO4, Na2HPO4, and NaH2PO4) with different pKa values. Let's break down the steps to find the answers to both parts of the question:

a) To prepare a buffer solution with pH 7.6, we need to select an appropriate ratio of the conjugate acid and base components such that their pKa values bracket the desired pH.

Step 1: Calculate the ratio of [base]/[acid] using the Henderson-Hasselbalch equation:
pH = pKa + log([base]/[acid])

Let's assume x represents the ratio [Na2HPO4]/[NaH2PO4].
7.6 = pKa2 + log(x)

Step 2: Calculate the concentration of each component in the buffer solution:
[Na2HPO4] = (0.10 M) * x
[NaH2PO4] = 0.10 M - [Na2HPO4]

Step 3: Calculate the volumes of each component required in a total volume of 500 ml:
V(Na2HPO4) = (0.10 M) * x * V_total
V(NaH2PO4) = (0.10 M - [Na2HPO4]) * V_total

b) To adjust the pH of the buffer solution after adding HCl, we need to calculate the amount of acid added by considering the volume and concentration.

Step 1: Calculate the moles of HCl required to change the pH:
moles(HCl) = (Volume) * (Concentration)

Step 2: Calculate the new concentrations of the conjugate acid and base:
[Na2HPO4] = (0.10 M) * x
[NaH2PO4] = (0.10 M - [Na2HPO4]) + (moles(HCl) / Volume_total)

Now, let's solve both parts of the question using the given equations and calculations.

you have 1.00 liter each of 0.10 M Na3PO4, Na2HPO4, NaH2po4 ka 1= 7.5*10^-3 ka2=6.2*10^-8 ka3=4.8*10^-13 a) prepare 500 ml of a buffer with PH= 7.6 b) how much 0.10 M HCL must be added to the 500ml of buffer to result in a PH=7.2 after the addition?

You want to use some of the NaH2PO4 as the acid and some of the Na2HPO4 as the base.

To prepare a buffer solution with a desired pH, we need to calculate the amounts of the conjugate acid and base needed. In this case, we have three components (Na3PO4, Na2HPO4, and NaH2PO4) with different pKa values. Let's break down the steps to find the answers to both parts of the question:

you have 1.00 liter each of 0.10 M Na3PO4, Na2HPO4, NaH2po4 ka 1= 7.510^-3 ka2=6.210^-8 ka3=4.8*10^-13 a) prepare 500 ml of a buffer with PH= 7.6 b) how much 0.10 M HCL must be added to the 500ml of buffer to result in a PH=7.2 after the addition?