AP Chemistry Flashcards: Acid Base Reactions And Buffers

What this deck covers

This deck focuses on Acid Base Reactions And Buffers, giving you a quick way to review the definitions, rules, and examples that matter most for AP Chemistry.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: Calculate the $pK_a$ for an acid with $K_a = 1.0 \times 10^{-5}$.

Answer: $pK_a = 5$. $pK_a = -\log(1.0 \times 10^{-5}) = 5$.

Flashcard 2: What is the pH of a neutral solution at 25°C?

Answer: pH = 7. Equal concentrations of $H^+$ and $OH^-$ ions.

Flashcard 3: What is the formula for calculating $pK_w$?

Answer: $pK_w = pH + pOH$. Sum equals 14 at 25°C for aqueous solutions.

Flashcard 4: Which strong acid completely dissociates in water?

Answer: Hydrochloric acid ($HCl$). Strong acid with 100% ionization in water.

Flashcard 5: What is the $K_b$ expression for ammonia $NH_3$?

Answer: $K_b = \frac{[NH_4^+][OH^-]}{[NH_3]}$. Products over reactants for base ionization equilibrium.

Flashcard 6: Identify the weak base in the ammonia-ammonium chloride buffer system.

Answer: Ammonia ($NH_3$). Weak base component that partially ionizes.

Flashcard 7: What is the formula to calculate pOH from hydroxide ion concentration?

Answer: p$OH = -\text{log}[OH^-]$. Negative log transforms $OH^-$ concentration to pOH scale.

Flashcard 8: Identify the conjugate acid of the base $NH_3$.

Answer: $NH_4^+$. Gains a proton from $NH_3$ to form ammonium ion.

Flashcard 9: What happens to the pH of a buffer when a small amount of acid is added?

Answer: pH decreases slightly. Buffer components neutralize added acid effectively.

Flashcard 10: Which strong base completely dissociates in water?

Answer: Sodium hydroxide ($NaOH$). Strong base with 100% dissociation in water.

Flashcard 11: What is the primary function of a buffer?

Answer: To maintain stable pH. Prevents large pH changes in chemical systems.

Flashcard 12: What is the relationship between $K_a$ and $K_b$ for a conjugate acid-base pair?

Answer: $K_a \times K_b = K_w$. Product equals water's ionization constant at 25°C.

Flashcard 13: Calculate the pH change when $0.01$ mol $HCl$ is added to a 1L buffer with $pK_a = 4.76$.

Answer: Minimal pH change. Buffer capacity prevents large pH shifts effectively.

Flashcard 14: Calculate the pOH of a solution with $[OH^-] = 1.0 \times 10^{-4} M$.

Answer: pOH = 4. pOH = $-\log(1.0 \times 10^{-4}) = 4$.

Flashcard 15: Calculate the $pK_a$ for an acid with $K_a = 1.0 \times 10^{-5}$.

Answer: $pK_a = 5$. $pK_a = -\log(1.0 \times 10^{-5}) = 5$.

Flashcard 16: Find the pH of a 0.1 M $HCl$ solution.

Answer: pH = 1. Strong acid completely ionizes: $[H^+] = 0.1$ M.

Flashcard 17: What is the Henderson-Hasselbalch equation for pH?

Answer: $\mathrm{pH} = \mathrm{p}K_a + \log \frac{[A^-]}{[HA]}$. Relates buffer pH to acid strength and base ratio.

Flashcard 18: What characteristic of a weak acid makes it suitable for a buffer?

Answer: Partial ionization. Incomplete dissociation provides buffering capacity.

Flashcard 19: Identify the weak acid in the acetic acid-sodium acetate buffer system.

Answer: Acetic acid ($CH_3COOH$). Weak acid component that partially ionizes.

Flashcard 20: Which ion is responsible for the acidity of a solution?

Answer: Hydrogen ion ($H^+$). Higher $H^+$ concentration means more acidic solution.

Flashcard 21: State the Bronsted-Lowry definition of a base.

Answer: Proton acceptor. Bases accept protons from other species in solution.

Flashcard 22: Identify the conjugate acid of the base $H_2O$.

Answer: $H_3O^+$. Water gains a proton to form hydronium ion.

Flashcard 23: Identify the conjugate base of the acid $HCl$.

Answer: $Cl^-$. Loses a proton from $HCl$ to form chloride ion.

Flashcard 24: What is the effect of dilution on the pH of a buffer?

Answer: Minimal change in pH. Buffer ratio remains constant during dilution process.

Flashcard 25: What defines a buffer solution?

Answer: Resists changes in pH upon addition of acid or base. Weak acid-base pair maintains stable pH range.

Flashcard 26: What is the concentration of $H^+$ in a solution with pH 4?

Answer: $1.0 \times 10^{-4} M$. $[H^+] = 10^{-4} = 1.0 \times 10^{-4}$ M.

Flashcard 27: Identify the conjugate base of the acid $H_2O$.

Answer: $OH^-$. Water loses a proton to form hydroxide ion.

Flashcard 28: Which ion is the conjugate base of $H_3PO_4$?

Answer: $H_2PO_4^-$. Loses one proton from phosphoric acid.

Flashcard 29: Which ion is the conjugate acid of $NH_2^-$?

Answer: $NH_3$. Gains a proton to form ammonia from amide ion.

Flashcard 30: Calculate the pH if $[OH^-] = 1.0 \times 10^{-5} M$ at 25°C.

Answer: pH = 9. pOH = 5, so pH = 14 - 5 = 9.