The correct formula for the ionic compound calcium hydroxide is: e. Ca(OH)2
The Correct Answer and Explanation is:
The correct formula for the ionic compound calcium hydroxide is:
e. Ca(OH)₂
Explanation:
To determine the formula of an ionic compound, it is important to consider the charges of the ions involved and how they combine to form a neutral compound.
Step 1: Identify the ions.
- Calcium (Ca) is a metal in Group 2 of the periodic table. It forms a +2 cation, written as Ca²⁺.
- Hydroxide (OH) is a polyatomic ion made up of one oxygen and one hydrogen atom. It has a -1 charge, written as OH⁻.
Step 2: Balance the charges.
Since calcium has a +2 charge and hydroxide has a -1 charge, you need two hydroxide ions to balance the +2 charge from one calcium ion:
- Ca²⁺ needs 2 OH⁻ to cancel out the positive charge: Ca²⁺ + 2 OH⁻ → Ca(OH)₂
Step 3: Write the formula.
When writing the formula, use parentheses around the polyatomic ion if you need more than one of them. This indicates that the entire OH group is present twice, not just the hydrogen.
So, the correct chemical formula is Ca(OH)₂, where:
- Ca represents one calcium ion.
- (OH)₂ shows two hydroxide ions.
Why this is important:
This formula tells you that calcium hydroxide consists of one calcium ion and two hydroxide ions in a 1:2 ratio. It also helps in predicting the compound’s behavior in water (it dissolves to give Ca²⁺ and OH⁻ ions), its use in neutralizing acids, and its role in construction (as limewater or slaked lime).
Therefore, the correct answer is Ca(OH)₂.
