pH 계산 문제 소개
안녕하세요, 오늘은 화학에서 자주 다루는 pH 계산 문제를 소개해드리려고 합니다. pH 계산은 산성도와 염기성을 이해하는 데 필수적인 개념으로, 다양한 상황에서 사용됩니다. 이번 포스트에서는 몇 가지 pH 계산 문제를 통해 개념을 쉽게 이해하고 연습할 수 있도록 도와드리겠습니다.
Problem 1: Calculate the pH of a 0.01 M HCl solution.
HCl is a strong acid that fully dissociates in water. Thus, [H+] = 0.01 M. The pH is calculated as follows: pH = -log(0.01) = 2.
Problem 2: Calculate the pH of a 0.1 M acetic acid solution (Ka = 1.8 × 10-5).
For a weak acid, [H+] = √(Ka · [HA]). Thus, [H+] = √(1.8 × 10-5 × 0.1) = 1.34 × 10-3 M. The pH is: pH = -log(1.34 × 10-3) ≈ 2.87.
Problem 3: Calculate the pH of a buffer solution containing 0.1 M acetic acid and 0.05 M sodium hydroxide (pKa = 4.74).
The reaction between acetic acid and sodium hydroxide produces acetate ion and water. The buffer solution contains 0.1 M acetate ion and 0.1 M acetic acid. Using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]) = 4.74 + log(0.1/0.1) = 4.74.
Problem 4: Calculate the pH of a 0.025 M HNO3 solution.
HNO3 is a strong acid that fully dissociates in water. Thus, [H+] = 0.025 M. The pH is calculated as follows: pH = -log(0.025) ≈ 1.60.
Problem 5: Calculate the pH of a 0.05 M ammonia solution (Kb = 1.8 × 10-5).
For a weak base, [OH-] = √(Kb · [B]). Thus, [OH-] = √(1.8 × 10-5 × 0.05) = 9.49 × 10-4 M. The pOH is: pOH = -log(9.49 × 10-4) = 3.02. The pH is: pH = 14 - pOH = 14 - 3.02 = 10.98.