how to determine the pH of a 200mL solution that contains 0.365g of dissolved HCl?

Answer 1

mols HCl = grams/molar mass = 0.365/36.5 = 0.01 mols.
Molarity = M = mols/L = 0.01 mol/0.200 L = 0.05 M = (H^+)
Then pH = -log(H^+). Substitute and solve.