Final answer:
To calculate the pH of a 0.2g HCIO solution in 150 mL of water, convert mass to moles, find molar concentration, use the Ka to determine [H3O+], and then calculate pH, which is approximately 3.56.
Step-by-step explanation:
The question you've asked involves calculating the pH of a weak acid solution, specifically hypochlorous acid (HCIO), when a certain mass is dissolved in water to form a solution of a given volume.
To find the pH, you need to determine the molar concentration of the acid in solution, use the provided acid dissociation constant (Ka) to find the concentration of hydronium ions (H3O+), and then use the pH formula.
Firstly, calculate the number of moles of HCIO: The molar mass of HCIO (H=1.01, Cl=35.45, O=16.00) is approximately 52.46 g/mol.
With 0.2g of HCIO, use the molar mass to convert grams to moles: 0.2 g / 52.46 g/mol ≈ 3.81 x 10-3 moles.
Next, divide the moles by the volume in liters to get the concentration of HCIO in the solution: 3.81 x 10-3 moles / 0.150 L = 2.54 x 10-2 M.
To calculate the pH, use the equation pH = -log[H3O+] and find [H3O+] using the Ka expression: [H3O+] = √(Ka x [HCIO]).
Plugging in the numbers: [H3O+] = √(3.0 x 10-7 x 2.54 x 10-2) ≈ 2.76 x 10-4 M.
Finally, calculate the pH: pH = -log(2.76 x 10-4) ≈ 3.56.