Which of the following substances, when added to water, will produce a solution with a pH greater than 7?
Show the answer and explanation
Correct answer
B. CaO
Principle or equation
Metal oxides (basic oxides) react with water to form bases, producing basic solutions (pH > 7). Nonmetal oxides (acidic oxides) form acids, producing acidic solutions.
Why this answer is correct
CaO (calcium oxide) is a metal oxide and reacts with water to form calcium hydroxide, Ca(OH)2, which is a strong base, so the solution is basic. SO2, CO2, and P2O5 are nonmetal oxides that form acidic solutions.
Example
Na2O reacts with water to form NaOH, giving a pH > 7.
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