31. In water, a base:

• A) Increases the concentration of ( OH^- ) ions
• B) Decreases the concentration of ( OH^- ) ions
• C) Increases the concentration of ( H^+ ) ions
• D) Remains neutral
• Answer: A

32. What is the ion-product constant for water (( K_w )) at 25°C?

• A) ( 1 \times 10^{-7} )
• B) ( 1 \times 10^{-14} )
• C) ( 1 \times 10^7 )
• D) ( 1 \times 10^{-10} )
• Answer: B

33. An acid with a pKa of 3 is:

• A) A weak acid
• B) A strong acid
• C) A weak base
• D) Neutral
• Answer: B

34. A strong base is one that:

• A) Completely ionizes in solution
• B) Partially ionizes in solution
• C) Does not ionize in solution
• D) Accepts a proton from any acid
• Answer: A

35. Which of the following is NOT an acid-base indicator?

• A) Phenolphthalein
• B) Bromothymol blue
• C) Litmus
• D) Glucose
• Answer: D

36. Which of the following pairs can form a buffer solution?

• A) HCl and NaCl
• B) ( CH_3COOH ) and ( CH_3COONa )
• C) H₂SO₄ and Na₂SO₄
• D) NaOH and KOH
• Answer: B

37. If the pH of a solution decreases, the concentration of H⁺ ions:

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

38. Which of the following acids is considered weak?

• A) ( HCl )
• B) ( H_2SO_4 )
• C) ( CH_3COOH )
• D) ( HNO_3 )
• Answer: C

39. The pH of a solution is related to the:

• A) Concentration of ( OH^- ) ions
• B) Concentration of ( H^+ ) ions
• C) Total number of moles
• D) Molecular weight
• Answer: B

40. Which of the following is the strongest base?

• A) NaOH
• B) KOH
• C) NH₃
• D) ( Ca(OH)_2 )
• Answer: A