buffer solutions examples

🧪 Quick Study Guide

• ⚖️ A buffer solution resists changes in pH when small amounts of acid or base are added.
• ⚗️ Buffers are typically made from a weak acid and its conjugate base, or a weak base and its conjugate acid.
• 📝 The Henderson-Hasselbalch equation helps calculate the pH of a buffer solution: $pH = pK_a + log(\frac{[A^-]}{[HA]})$ where $[A^-]$ is the concentration of the conjugate base and $[HA]$ is the concentration of the weak acid.
• ➕ Adding a strong acid to a buffer neutralizes the conjugate base, shifting the equilibrium towards the weak acid.
• ➖ Adding a strong base to a buffer neutralizes the weak acid, shifting the equilibrium towards the conjugate base.
• 🌡️ Buffer capacity is the amount of acid or base a buffer can neutralize before significant pH change occurs.
• 🌱 Buffers are crucial in biological systems to maintain stable pH levels for enzymes and other biological processes to function properly.

Practice Quiz

1. Which of the following pairs could form a buffer solution?

   1. A. HCl and NaCl
   2. B. NaOH and NaCl
   3. C. $CH_3COOH$ and $CH_3COONa$
   4. D. $HNO_3$ and $KNO_3$

2. What is the main function of a buffer solution?

   1. A. To increase the pH of a solution
   2. B. To decrease the pH of a solution
   3. C. To resist changes in pH
   4. D. To catalyze reactions

3. Which equation is used to calculate the pH of a buffer solution?

   1. A. $pH = -log[H^+]$
   2. B. $pH + pOH = 14$
   3. C. $pH = pK_a + log(\frac{[A^-]}{[HA]})$
   4. D. $pH = pK_b + log(\frac{[HB^+]}{[B]})$

4. What happens when a strong acid is added to a buffer solution containing a weak acid (HA) and its conjugate base (A-)?

   1. A. The pH increases significantly.
   2. B. The strong acid reacts with the weak acid (HA).
   3. C. The strong acid reacts with the conjugate base (A-).
   4. D. The buffer becomes more basic.

5. What determines the buffer capacity of a buffer solution?

   1. A. The $pK_a$ of the weak acid.
   2. B. The volume of the solution.
   3. C. The concentration of the salt.
   4. D. The concentrations of the weak acid and its conjugate base.

6. Which of the following is an example of a buffer system in the human body?

   1. A. Hydrochloric acid in the stomach
   2. B. Sodium chloride in sweat
   3. C. Carbonic acid/bicarbonate in blood
   4. D. Phosphoric acid in urine

7. A buffer solution is prepared with 0.2 M $NH_3$ and 0.25 M $NH_4Cl$. What will happen to the pH if you add a small amount of HCl?

   1. A. The pH will increase significantly.
   2. B. The pH will decrease significantly.
   3. C. The pH will remain relatively stable.
   4. D. The solution will become neutral.