Determine the pH of the Solution
Calculating the pH of the Solution
Calculate the pH of the solution formed when 45ml of a 0.15M hypochlorous acid, 45ml of a 0.10M sodium hypochlorite, and 10ml of a 0.10M hydrogen bromide solution are mixed together. Assume that volumes are additive.
The first step is to write down the reaction equations for the acid-base reactions that will take place. The hypochlorous acid (HOCl) is a weak acid, and the sodium hypochlorite (NaOCl) is a salt of a weak acid and a strong base. The hydrogen bromide (HBr) is a strong acid.
The reaction equations are:
- HOCl + H2O <=> H3O+ + Cl-
- NaOCl + H2O <=> NaOH + HCl
- HBr + H2O <=> H3O+ + Br-
The next step is to determine the number of moles of each reactant that are present. The total volume of the solution is 45 + 45 + 10 = 100 mL. So the number of moles of HOCl is 6.75 mmol, the number of moles of NaOCl is 4.50 mmol, and the number of moles of HBr is 1.00 mmol.
The limiting reactant is the HBr since it will be used up first. The concentration of H3O+ is 0.010 M and the concentration of Cl- is 0.0575 M.
The pH of the solution is calculated using the equation:
pH = -log(H3O+)
Plugging in the concentration of H3O+, we get:
pH = -log(0.010) = 2.0
Final answer: The pH of the solution is 2.0.
Explanation: The pH of the solution is 2.0 because of the concentration of H3O+ ions in the solution.