酸和鹼的計算問題

1.
HA is a monobasic weak acid.
(a) Write an equationto show the ionization of the acid in aqueous solution.
(b) Besides H2O molecules, what particles (molecules or ions) are present in the aqueous solution?

(a) HA(aq) ⇌ H⁺(aq) + A⁻(aq)

(b) HA(aq) molecules, H⁺(aq) ions, A⁻(aq) ions, and a small amount of OH⁻(aq) ions.


= = = = =
2.
(a) What is the molar concentration of hydrogen ion is 0.1 M HCl(aq)? Explain your answer.
(b) Calculate the pH of 0.1 M HCl(aq).
(c) Explain the fact that the pH of 0.1 M CH3COOH(aq) is not the same as that of 0.1 M HCl(aq).

(a)
0.1 M
This is because HCl is a strong monobasic acid, and 0.1 M HCl is completely ionized in water to give 0.1 M H⁺(aq) ions.

(b)
pH = -log[H⁺] = -log(0.1) = 1

(c)
CH3COOH is a weak monobasic acid which is only partly ionized in water to give H⁺(aq) ions.
Therefore, [H⁺] < 0.1 M
and thus pH = -log[H⁺] > 1

1a HA -> H+ + A-
b OH-, H+, A-, HA
2a 0.1 M ,HCl totally ionizes to H+ and Cl-
b pH = -log 0.1 = 1
c CH3COOH is a weak acid, not totally ionized in water. 1 mole of it gives less than 1 mole of H+, lower conc. of H+ --> higher pH