The acetate ion C2H3O2- has a charge of -1. What is the correct formula for calcium acetate?
a) Ca2(C2H3O2)2.
b) Ca(C2H3O2)3.
c) CaC2H3O2.
d) Ca(C2H3O2)2.
The Correct Answer and Explanation is :
The correct formula for calcium acetate is d) Ca(C2H3O2)2.
Explanation:
- Calcium Ion (Ca²⁺):
Calcium is a metal in group 2 of the periodic table, meaning it forms ions with a +2 charge. This is because it loses two electrons to achieve a stable electron configuration. - Acetate Ion (C₂H₃O₂⁻):
The acetate ion is a polyatomic ion with the formula C₂H₃O₂⁻ (sometimes written as CH₃COO⁻), which has a -1 charge. Acetate comes from acetic acid (CH₃COOH) and carries a negative charge after losing a proton (H⁺). - Balancing Charges:
In order to form a neutral ionic compound, the total positive charge must balance the total negative charge. Since the calcium ion has a +2 charge (Ca²⁺) and the acetate ion has a -1 charge (C₂H₃O₂⁻), you need two acetate ions to balance one calcium ion.
- Calcium ion: Ca²⁺ (charge = +2)
- Acetate ion: C₂H₃O₂⁻ (charge = -1) To balance the charges:
[
\text{1 calcium ion (Ca²⁺)} \text{ requires 2 acetate ions (C₂H₃O₂⁻) to balance the charges, resulting in a neutral compound.}
]
- Formula:
The formula for calcium acetate is therefore Ca(C₂H₃O₂)₂. The parentheses around C₂H₃O₂ indicate that two acetate ions are present, as required to balance the +2 charge of the calcium ion. Without the parentheses, it would incorrectly imply just one acetate ion.
In summary, the correct formula is Ca(C₂H₃O₂)₂, which ensures charge neutrality between the calcium and acetate ions.