Which of the following represents the correct formula for calcium oxide?

Question

Examoogle · Accepted Answer

The correct answer is Option D: $	ext{CaO}$. Calcium oxide is an ionic compound formed by the combination of calcium ions ($Ca^{2+}$) and oxide ions ($O^{2-}$). Since the positive and negative charges balance out in a 1:1 ratio, the simplest chemical formula is $CaO$.

Step-by-Step Solution & Concepts:
Calcium oxide is an ionic compound formed by the combination of calcium ions ($Ca^{2+}$) and oxide ions ($O^{2-}$). Since the positive and negative charges balance out in a 1:1 ratio, the simplest chemical formula is $CaO$.

Working Principle: In the formation of calcium oxide, a calcium atom (group 2, alkaline earth metal) loses its two valence electrons to form a calcium ion with a $+2$ charge ($Ca^{2+}$). An oxygen atom (group 16, chalcogen) gains these two electrons to achieve a stable octet, forming an oxide ion with a $-2$ charge ($O^{2-}$). The electrostatic attraction between these oppositely charged ions creates an ionic bond, resulting in the electrically neutral formula $CaO$.

Key Formulas: $Ca^{2+} + O^{2-} ightarrow CaO$ — Formation of ionic bond between calcium and oxygen; $CaO + H_2O ightarrow Ca(OH)_2$ — Reaction of quicklime (calcium oxide) with water to form slaked lime

Key Points: Calcium is a divalent cation ($Ca^{2+}$); Oxygen is a divalent anion ($O^{2-}$); Ionic compounds are represented by the empirical formula, which is the simplest whole-number ratio of ions; Commonly known as quicklime or burnt lime

Advantages: Used extensively in the production of cement; Acts as a drying agent in laboratory settings; Important for neutralizing acidic soils in agriculture

Applications: Manufacturing of steel and glass; Water treatment and sewage processing

Additional Info: Calcium oxide is widely referred to as 'quicklime' in industrial chemistry.. Option A ($Ca_2O$) is incorrect as it implies an unbalanced charge ratio.. Option B ($CaO_2$) is the formula for calcium peroxide, a different compound.. Option C ($Ca_2O_3$) is chemically incorrect as these valencies do not combine in this ratio.

Answer: D is correct — The chemical formula for calcium oxide is $CaO$, as it consists of one calcium ion ($Ca^{2+}$) and one oxide ion ($O^{2-}$), resulting in a neutral ionic compound.

Exam Tip: Remember that for ionic compounds, you always criss-cross the valencies and simplify to the lowest whole-number ratio. For $Ca^{2+}$ and $O^{2-}$, the ratio $2:2$ simplifies to $1:1$.

Examoogle · Answer

Option A: $	ext{Ca}_2	ext{O}$

Examoogle · Answer

Option B: $	ext{CaO}_2$

Examoogle · Answer

Option C: $	ext{Ca}_2	ext{O}_3$

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