Question

What does calcium oxide produce when it reacts vigorously with water?

• A. Calcium carbonate
• B. Calcium hydroxide
• C. Calcium sulphate
• D. Calcium phosphate

Hint:

The reaction of quicklime with water is a classic example of both a combination reaction and a highly exothermic reaction.
- Quicklime = CaO
- Slaked lime = \(\text{Ca(OH)}_2\)

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the name of the chemical product formed when calcium oxide (commonly known as quicklime) reacts vigorously with water.

Step 2: Key Formula or Approach:
Write down the chemical reaction of a metal oxide with water:
\[ \text{CaO} + \text{H}_2\text{O} \to \text{Ca(OH)}_2 \]

Step 3: Detailed Explanation:

• Calcium oxide (CaO), or quicklime, is a highly reactive basic oxide.

• When water is added to calcium oxide, a highly exothermic combination reaction takes place.

• The reaction produces slaked lime, which is chemically known as calcium hydroxide [\(\text{Ca(OH)}_2\)]:
\[ \text{CaO(s)} + \text{H}_2\text{O(l)} \to \text{Ca(OH)}_2\text{(aq)} + \text{Heat} \] - This reaction releases a large amount of heat energy, causing the water to boil and hiss.

• Calcium hydroxide formed is used extensively in whitewashing and soil treatment.


Step 4: Final Answer:
Calcium oxide produces calcium hydroxide when it reacts with water.