A solution of NaOH(aq) contains 5.2 g of NaOH(s) per 100.0 mL of solution. Calculate the pH and the pOH of the solution at 25 °C.
mols NaOH = grams/molar mass
M NaOH = mols/L solution. L soln = 0.1 L in the problem.
Then (OH^-) = (NaOH)
pOH = -log(OH^-)
pH + pOH = pKw = 14. You know pOH and pKw, solve for pH.
Post your work if you get stuck.
2314
To calculate the pH and pOH of the NaOH solution, we first need to determine the concentration of hydroxide ions (OH-) in the solution.
Given:
Mass of NaOH(s) = 5.2 g
Volume of solution = 100.0 mL = 0.100 L
Step 1: Calculate the number of moles of NaOH
The molar mass of NaOH is 22.99 g/mol + 16.00 g/mol + 1.01 g/mol = 39.99 g/mol.
Therefore, the number of moles of NaOH is:
moles of NaOH = mass of NaOH / molar mass of NaOH
moles of NaOH = 5.2 g / 39.99 g/mol = 0.130 mol
Step 2: Calculate the concentration of OH- ions
The volume of the solution is 0.100 L, and we have 0.130 mol of NaOH in that volume.
Concentration of OH- ions = moles of NaOH / volume of solution
Concentration of OH- ions = 0.130 mol / 0.100 L = 1.30 M
Step 3: Calculate the pOH
The pOH is defined as the negative logarithm (base 10) of the hydroxide ion concentration.
pOH = -log[OH-]
pOH = -log(1.30) = 0.113
Step 4: Calculate the pH
pH and pOH are related by the equation:
pH + pOH = 14
Therefore,
pH = 14 - pOH
pH = 14 - 0.113 = 13.887
So, the pH of the NaOH solution is approximately 13.887, and the pOH is approximately 0.113.