Which of the following oxides, when dissolved in water, produces a solution with a pH less than 7?
Show the answer and explanation
Correct answer
C. SO2
Principle or equation
Metal oxides are basic and react with water to form bases (pH>7); non-metal oxides are acidic and form acids (pH<7).
Why this answer is correct
SO2 is a non-metal oxide; it reacts with water to form sulfurous acid (H2SO3), which is acidic, so pH<7. The others are metal oxides that form strong bases.
Example
CO2 dissolves to form carbonic acid, lowering pH.
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