AP Chemistry Questions on pH Calculations: Exam Prep

🧪 Quick Study Guide

• 💧 pH Scale: Measures the acidity or alkalinity of a solution. Ranges from 0-14, where 7 is neutral, below 7 is acidic, and above 7 is basic.
• ➗ pH Formula: $pH = -log[H^+]$, where $[H^+]$ is the concentration of hydrogen ions.
• ➕ pOH Formula: $pOH = -log[OH^-]$, where $[OH^-]$ is the concentration of hydroxide ions.
• ⚖️ Relationship between pH and pOH: $pH + pOH = 14$ at $25^\circ C$.
• ↔️ Acid Dissociation Constant ($K_a$): Indicates the strength of an acid. A larger $K_a$ means a stronger acid.
• 🔄 Base Dissociation Constant ($K_b$): Indicates the strength of a base. A larger $K_b$ means a stronger base.
• 🌡️ Ion Product of Water ($K_w$): $K_w = [H^+][OH^-] = 1.0 \times 10^{-14}$ at $25^\circ C$.
• 🧮 Calculating pH of Weak Acids/Bases: Use ICE tables (Initial, Change, Equilibrium) to determine the equilibrium concentrations of $H^+$ or $OH^-$.

Practice Quiz

1. What is the pH of a 0.01 M solution of HCl?
   1. 2
   2. 12
   3. -2
   4. 0.01
2. What is the pOH of a solution with a pH of 9?
   1. 5
   2. -9
   3. 14
   4. 9
3. The concentration of $H^+$ in a solution is $1.0 \times 10^{-5}$ M. What is the pH?
   1. 5
   2. 9
   3. -5
   4. 1 \times 10^{-9}
4. What is the pH of pure water at $25^\circ C$?
   1. 0
   2. 14
   3. 7
   4. 1
5. A solution has a pH of 3. What is the concentration of $H^+$ ions?
   1. $1 \times 10^{-3}$ M
   2. $3 \times 10^{-1}$ M
   3. $1 \times 10^{3}$ M
   4. $1 \times 10^{-11}$ M
6. If the $K_w$ is $1.0 \times 10^{-14}$, what are the concentrations of $H^+$ and $OH^-$ in pure water at $25^\circ C$?
   1. $[H^+] = 1.0 \times 10^{-7}$ M, $[OH^-] = 1.0 \times 10^{-7}$ M
   2. $[H^+] = 1.0 \times 10^{-14}$ M, $[OH^-] = 1.0 \times 10^{0}$ M
   3. $[H^+] = 0$ M, $[OH^-] = 1.0 \times 10^{-14}$ M
   4. $[H^+] = 1.0 \times 10^{0}$ M, $[OH^-] = 1.0 \times 10^{-14}$ M
7. What is the effect of increasing temperature on the pH of pure water?
   1. pH increases
   2. pH decreases
   3. pH remains constant
   4. pH becomes undefined