7. A solution is prepared by dissolving 8.5 g NaHCO3 and 12.7 g Na2CO3 in 500.0 mL of water. Calculate the pH.

To calculate the pH of the solution, we need to determine the concentration of hydroxide ions (OH-) or hydronium ions (H3O+), as well as the concentration of sodium ions (Na+).

First, let's find the concentration of sodium ions (Na+):
1. Calculate the moles of NaHCO3:
- NaHCO3 molar mass = 22.99 g/mol (Na) + 1.01 g/mol (H) +
12.01 g/mol (C) + 3 * 16.00 g/mol (O) = 84.01 g/mol
- Moles of NaHCO3 = mass / molar mass = 8.5 g / 84.01 g/mol = 0.101 mol

2. Calculate the moles of Na2CO3:
- Na2CO3 molar mass = 2 * 22.99 g/mol (Na) + 12.01 g/mol (C) +
3 * 16.00 g/mol (O) = 105.99 g/mol
- Moles of Na2CO3 = mass / molar mass = 12.7 g / 105.99 g/mol = 0.120 mol

3. Calculate the total moles of sodium ions:
- Total moles of Na+ = moles of NaHCO3 + 2 * moles of Na2CO3
= 0.101 mol + 2 * 0.120 mol = 0.341 mol

Next, let's determine the concentration of hydroxide ions (OH-) or hydronium ions (H3O+):

4. Calculate the volume of the solution in liters:
- Volume of the solution = 500.0 mL = 500.0 mL / 1000 mL/L = 0.500 L

5. Calculate the concentration of sodium ions (Na+):
- Na+ concentration = moles of Na+ / volume of the solution
= 0.341 mol / 0.500 L = 0.682 M

6. Since Na+ is the conjugate acid of OH-, the concentration of OH- is also 0.682 M.

7. Calculate the concentration of hydronium ions (H3O+):
- Since we have an ionic compound dissolved in water, we can assume complete ionization.
- Therefore, the concentration of H3O+ is equal to the concentration of OH-,
which is 0.682 M.

8. Finally, calculate the pH:
- pH = -log[H3O+]
- pH = -log(0.682)
- pH ≈ 0.166

Therefore, the pH of the solution is approximately 0.166.

To calculate the pH of a solution, you need to know the concentration or molarity of the hydrogen ion concentration ([H+]). In this case, the information provided is the mass of the solute (sodium bicarbonate and sodium carbonate) and the volume of the solution.

To find the [H+], you can calculate the molarities of the two solutes separately, then use the dissociation equations to find the concentration of H+ ions. Finally, you can convert the concentration of H+ ions into pH using the formula for pH.

Here are the steps to calculate the pH:

Step 1: Convert the mass of each solute to moles.

The molar mass of NaHCO3 (sodium bicarbonate) is:
Na = 22.99 g/mol
H = 1.01 g/mol
C = 12.01 g/mol
O = 16.00 g/mol

Using these values, you can calculate the moles of NaHCO3:
moles of NaHCO3 = mass of NaHCO3 / molar mass of NaHCO3

Similarly, calculate the moles of Na2CO3 (sodium carbonate):
moles of Na2CO3 = mass of Na2CO3 / molar mass of Na2CO3

Step 2: Calculate the molarities of NaHCO3 and Na2CO3.

Molarity (M) = moles of solute / volume of solution (in liters)

Convert the volume of water to liters:
volume of solution = 500.0 mL = 500.0 mL / 1000 mL/L = 0.500 L

Calculate the molarity of NaHCO3:
Molarity of NaHCO3 = moles of NaHCO3 / volume of solution

Similarly, calculate the molarity of Na2CO3.

Step 3: Calculate the concentration of H+ ions.

The dissociation equation for NaHCO3 is:
NaHCO3 -> Na+ + HCO3-

From this equation, you can see that 1 mole of NaHCO3 produces 1 mole of HCO3- ions. Therefore, the concentration of H+ ions is equal to the concentration of HCO3- ions.

Use the molarity of NaHCO3 to calculate the concentration of H+ ions.

Similarly, calculate the concentration of H+ ions for Na2CO3. The dissociation equation for Na2CO3 is:
Na2CO3 -> 2Na+ + CO3^2-

Step 4: Calculate the pH.

The pH can be calculated using the concentration of H+ ions using the formula:
pH = -log10[H+]

Calculate the pH using the concentration of H+ ions obtained from both NaHCO3 and Na2CO3.

By following these steps and performing the necessary calculations, you should be able to determine the pH of the solution.

Use the Henderson Hasselbalch equation.