A pH = 7.6 buffer is needed in the lab. This buffer is made by first dissolving 17.42 g K2HPO4 in 600 mL of water. What is the pH of this salt solution? This solution of course will be too basic becuase we only have the base of the buffer present.

What must the value of the ratio of [H2PO4-]/[HPO42-] be to create a buffer solution that is pH = 7.6?

How many moles of HCl must be added to the 600 mL solution of HPO42-(aq) to prepare the pH = 7.6 buffer solution?

How many mL of 0.5 M HCl must be added to the solution to create the pH = 7.6 buffer solution?

And you know how to do how much of this? Start by explaining what you don't understand

ph=4 fpr number 10

To determine the pH of the salt solution made from dissolving K2HPO4, we need to consider the dissociation of the compound in water. K2HPO4 dissociates into two K+ ions and one HPO42- ion.

Step 1: Convert the mass of K2HPO4 to moles by using its molar mass. The molar mass of K2HPO4 is 174.18 g/mol.

Moles of K2HPO4 = 17.42 g / 174.18 g/mol = 0.100 mol

Step 2: Calculate the concentration of HPO42- ions in the solution. Since we have 600 mL of water, we assume the final volume of the solution is also 600 mL.

Concentration of HPO42- = moles of HPO42- / volume of solution
= 0.100 mol / 0.600 L = 0.167 M

Step 3: Use the Henderson-Hasselbalch equation to find the pH of the salt solution:

pH = pKa + log([A-]/[HA])

Since K2HPO4 is a basic compound, we can assume it acts as a weak base. The acid formed by its dissociation is HPO42-, and its conjugate base is H2PO4-.

The pKa value for the HPO42-/H2PO4- buffer system is given as 7.2 (approximately).

Thus, we have:

pH = 7.2 + log([H2PO4-]/[HPO42-])

Rearranging the equation, we get:

[H2PO4-]/[HPO42-] = 10^(pH - pKa)

[H2PO4-]/[HPO42-] = 10^(7.6 - 7.2) = 10^0.4 = 2.512

So, the value of the ratio [H2PO4-]/[HPO42-] in the buffer solution needs to be approximately 2.512.

Now, to determine the amount of HCl required to prepare the pH = 7.6 buffer solution:

Step 1: Calculate the moles of HPO42- present in the solution. We know that the concentration of HPO42- is 0.167 M and the volume is 600 mL.

Moles of HPO42- = concentration × volume
= 0.167 mol/L × 0.600 L = 0.1002 mol

Step 2: The moles of HCl required will be equal to the moles of HPO42- present, as we need to neutralize it and form H2PO4-. Therefore, we will also need 0.1002 mol of HCl.

To find the volume of the 0.5 M HCl solution required to prepare the pH = 7.6 buffer solution:

Step 1: Use the formula for molarity (M) to determine the moles of HCl required.

Moles of HCl = Molarity × Volume (in L)

Rearrange the equation: Volume (in L) = Moles of HCl / Molarity

Volume = 0.1002 mol / 0.5 mol/L = 0.2004 L = 200.4 mL

Approximately 200.4 mL of 0.5 M HCl solution should be added to the solution to create the pH = 7.6 buffer solution.