Answer to Question #108734 in General Chemistry for Vart Vars Megerditchian

Question

Calculate the pH of a solution made by dissolving 50.0 mL of hydrogen chloride in water at 25 0C and 1.00 atm. The total volume of that solution is 455 mL.

Answer 1

pH=-lg[H⁺]

[H⁺]=c_HCl - because HCl is a strong acid in aqueous solutions, i.e. it dissociates into H⁺ and Cl^- ions completely.

c_HCl=n_HCl/V_solution

V_solution=455mL=0.455L - the total volume of that solution is 455 mL

n_HCl=50.0*10^-3L / 22.4L*mol^-1=0.00223mol, (22.4L*mol^-1 - molar volume of gas under STD: 25 0C and 1.00 atm.)

[H⁺]=c_HCl=0.00223mol / 0.455L=0.005mol/L

pH=-lg[H⁺]=-lg(0.005)=2.3

Answer: pH=2.3