21. A buffer solution contains a weak acid and its:

• A) Strong conjugate base
• B) Weak conjugate base
• C) Salt
• D) Strong acid
• Answer: B

22. If the pH of a solution is decreased, the hydrogen ion concentration:

• A) Increases
• B) Decreases
• C) Remains constant
• D) Becomes neutral
• Answer: A

23. Which of the following statements about pH is true?

• A) pH is a logarithmic scale.
• B) pH cannot be negative.
• C) A decrease in pH means an increase in acidity.
• D) Both A and C are true.
• Answer: D

24. Which of the following is the strongest acid?

• A) Acetic acid (pKa ≈ 4.76)
• B) Hydrochloric acid (HCl)
• C) Formic acid (pKa ≈ 3.75)
• D) Citric acid (pKa ≈ 3.13)
• Answer: B

25. Which of the following will increase the pH of a solution?

• A) Adding hydrochloric acid
• B) Adding sodium hydroxide
• C) Adding acetic acid
• D) Adding ammonium chloride
• Answer: B

26. A solution with a pH of 10 is:

• A) Neutral
• B) Acidic
• C) Basic
• D) Alkaline
• Answer: C

27. What is the effect of dilution on a buffer solution?

• A) It completely neutralizes the buffer
• B) It has no effect on pH
• C) It decreases the buffer capacity
• D) Both B and C are true
• Answer: D

28. In a buffer solution, if the concentration of the weak acid is increased, the pH:

• A) Increases
• B) Decreases
• C) Remains the same
• D) Cannot be determined
• Answer: B

29. The pH of blood is normally maintained between:

• A) 6.0 – 6.5
• B) 7.35 – 7.45
• C) 7.0 – 8.0
• D) 6.8 – 7.2
• Answer: B

30. Which of the following buffers is best suited for maintaining a pH of around 4.75?

• A) Acetic acid and sodium acetate
• B) Ammonium chloride and ammonia
• C) Phosphate buffer
• D) Bicarbonate buffer
• Answer: A