What is the pH of a solution formed by mixing 14.35 mL of 0.200 F HCl with 0.322 g of Na3PO4, followed by dilution to 500.00 mL?
Determine the mols Na3PO4 in 0.322 g Na3PO4 and mols HCl in 14.35 mL of 0.200 F HCl.
Determine how much HPO4= is formed and how much HCl remains.
Determine how much H2PO4- is formed from the remaining HCl.
Use the Henderson-Hasselbalch equation with HPO4= = base and H2PO4- the acid.
Check my thinking. Post your work if you get stuck.
wouldn't you do it a different way since the Na3PO4 is a salt?
and what would you do with the 500 mL dilution after everything?
What do you have in mind?
dilution just changes the concentration.
concn = mols/L. And both salt and acid are diluted to the same volume.
To find the pH of the solution, we need to first calculate the number of moles of HCl and Na3PO4 in the solution, and then determine the concentration of H+ ions in the solution. Finally, we can calculate the pH using the concentration of H+ ions.
Step 1: Calculate the moles of HCl and Na3PO4
Moles of HCl = volume (in liters) × molarity
Given: volume = 14.35 mL = 0.01435 L
Molarity = 0.200 F (Note: F = normality, which is equivalent to moles per liter for HCl)
Moles of HCl = 0.01435 L × 0.200 mol/L = 0.00287 moles
Moles of Na3PO4 = mass / molar mass
Given: mass = 0.322 g
Molar mass of Na3PO4 = (3 × atomic mass of Na) + atomic mass of P + (4 × atomic mass of O)
Atomic mass of Na = 22.99 g/mol
Atomic mass of P = 30.97 g/mol
Atomic mass of O = 16.00 g/mol
Molar mass of Na3PO4 = (3 × 22.99) + 30.97 + (4 × 16.00) = 163.94 g/mol
Moles of Na3PO4 = 0.322 g / 163.94 g/mol = 0.00196 moles
Step 2: Calculate the concentration of H+ ions
The balanced equation for the reaction between HCl and Na3PO4 is:
3 HCl + Na3PO4 → 3 NaCl + H3PO4
From the balanced equation, we can see that for every 3 moles of HCl, we have 1 mole of H3PO4. Since H3PO4 is a weak acid, it will partially dissociate in water, releasing H+ ions.
So, in our solution, the concentration of H+ ions will be the moles of H3PO4 divided by the total volume of the solution.
Total volume of the solution = 500.00 mL = 0.500 L
Moles of H3PO4 = 0.00196 moles
Concentration of H+ ions = moles of H3PO4 / total volume of solution = 0.00196 moles / 0.500 L = 0.00392 M
Step 3: Calculate the pH
pH is defined as the negative logarithm of the concentration of H+ ions.
pH = -log[H+]
pH = -log(0.00392)
pH ≈ 2.41
Therefore, the pH of the solution is approximately 2.41.