Question

Write the formula for the following compounds: (a) Calcium hypochlorite, used as a swimming pool disinfectant (b) Copper(II) sulfate, used to kill algae in swimming pools (c) Sodium phosphate, used in detergents to enhance cleaning action

Short answer

(a) Ca(OCl)_2, (b) CuSO_4, (c) Na_3PO_4.

Step-by-step solution

Understanding Calcium Hypochlorite

Calcium hypochlorite's chemical composition includes calcium (Ca), and the hypochlorite ion and its formula is represented by Ca(OCl)_2. Calcium commonly forms a 2+ ion (Ca^{2+}), and the hypochlorite ion is OCl^-. Thus, combining one calcium ion with two hypochlorite ions balances the charge, resulting in the formula Ca(OCl)_2.

Deriving Copper(II) Sulfate Formula

Copper(II) sulfate's name indicates the presence of copper ions with a 2+ charge (Cu^{2+}) and the sulfate ion (SO_4^{2-}). Since sulfate also has a 2- charge, one copper ion balances one sulfate ion. Therefore, the chemical formula for copper(II) sulfate is CuSO_4.

Formulating Sodium Phosphate

Sodium phosphate consists of sodium ions (Na^+) and phosphate ions (PO_4^{3-}). Since the phosphate ion has a 3- charge, it requires three sodium ions to balance the charge. Hence, the formula for sodium phosphate is Na_3PO_4.

Key concepts

Ionic Compounds

Ionic compounds are formed when atoms transfer electrons between each other, creating charged particles called ions. This typically occurs between metals and nonmetals. Metals lose electrons, forming positive ions or cations, while nonmetals gain electrons, forming negative ions or anions. Consequently, the two opposite charges attract, forming a stable ionic bond.

• Example: Calcium hypochlorite (Ca(OCl)_2) is an ionic compound composed of calcium ions (Ca^{2+}) and hypochlorite ions (OCl^-).

These compounds usually form crystal lattice structures, leading to unique properties such as high melting points, and the ability to conduct electricity in molten or dissolved states. Understanding ionic compounds is crucial for recognizing how compounds like Calcium hypochlorite disinfect swimming pools. The ionic bonds ensure the compound’s stability in water.

Chemical Nomenclature

Chemical nomenclature is the systematic method of naming chemical compounds. It provides a standardized way to communicate complex chemical information.

• Ionic Compounds Naming: Typically, the name begins with the cation (metal) followed by the anion (nonmetal) with an "-ide" ending. For polyatomic ions like sulfate (SO_4^{2-}) or phosphate (PO_4^{3-}), the name of the ion is retained.
• Transition Metals: For elements like copper in Copper(II) sulfate, the Roman numeral indicates the charge on the metal, owing to the fact that transition metals can form multiple cations with different charges.

Correct naming ensures that there is no ambiguity in identifying or understanding a compound's composition and potential interactions. For instance, reading Copper(II) sulfate immediately informs one of copper's 2+ charge, influencing how one would predict the compound's behavior in chemical reactions.

Balance of Charges

A primary principle in forming ionic compounds is the balance of charges. Compounds must be electrically neutral, meaning the sum of positive and negative charges must equal zero.

• Example 1: In Calcium hypochlorite (Ca(OCl)_2), one Ca^{2+} balances with two OCl^- ions, as the charges add up to zero: (+2) + 2(-1) = 0.
• Example 2: For Copper(II) sulfate (CuSO_4), a Cu^{2+} ion perfectly balances with an SO_4^{2-} ion, because (+2) + (-2) = 0.
• Example 3: Sodium phosphate (Na_3PO_4) needs three Na^{+} ions to balance one PO_4^{3-} ion, making the total charge zero: 3(+1) + (-3) = 0.

Understanding how to balance charges is fundamental in writing correct chemical formulas and knowing how substances like these interact in solutions, such as in cleaning or disinfection applications.

Chemical Composition

The chemical composition of a compound reveals the identities and ratios of its constituent elements. It helps predict properties and behaviors of compounds in various conditions.

• Identifying Elements: By reading a chemical formula, one can determine the elements present. For example, Ca(OCl)_2 reveals calcium and hypochlorite in its make-up.
• Element Ratios: The subscripts in a formula indicate the ratio of ions or atoms in a compound. Na_3PO_4 tells us that there are three sodium ions for each phosphate ion.

This knowledge is not merely academic. Identifying such compositions allows scientists to tailor formulas to specific needs. Sodium phosphate, present in detergents, uses its specific ratio to effectively enhance cleaning action through its interaction with other substances in the wash.