Problem 73 - Chemistry: The Central Science

Question

Write the chemical formulas for the following compounds: (a) aluminum hydroxide, (b) potassium sulfate, (c) copper(I) oxide, (d) zinc nitrate, (e) mercury(II) bromide, (f) iron(III) carbonate, (g) sodium hypobromite.

Step-by-Step Solution

Answer

The chemical formulas for the given compounds are: (a) Al(OH)_3 (b) K_2SO_4 (c) Cu_2O (d) Zn(NO_3)_2 (e) HgBr_2 (f) Fe_2(CO_3)_3 (g) NaBrO

Step 1: (a) Aluminum Hydroxide

Aluminum has a charge of +3 and the hydroxide ion has a charge of -1. To combine these ions and produce a neutral compound, we need only one aluminum ion and three hydroxide ions. Thus, the formula is Al(OH)_3.

Step 2: (b) Potassium Sulfate

Potassium has a charge of +1 and sulfate has a charge of -2. To combine these ions to form a neutral compound, we need two potassium ions for every sulfate ion. Thus, the formula is K_2SO_4.

Step 3: (c) Copper(I) Oxide

Copper(I) has a charge of +1, while oxide has a charge of -2. To combine these ions to form a neutral compound, we need two copper ions for every oxide ion. Thus, the formula is Cu_2O.

Step 4: (d) Zinc Nitrate

Zinc has a charge of +2, while nitrate has a charge of -1. To combine these ions to form a neutral compound, we need one zinc ion for every two nitrate ions. Thus, the formula is Zn(NO_3)_2.

Step 5: (e) Mercury(II) Bromide

Mercury(II) has a charge of +2, while bromide has a charge of -1. To combine these ions to form a neutral compound, we need one mercury ion for every two bromide ions. Thus, the formula is HgBr_2.

Step 6: (f) Iron(III) Carbonate

Iron(III) has a charge of +3, while carbonate has a charge of -2. To combine these ions to form a neutral compound, we need two iron ions for every three carbonate ions. Thus, the formula is Fe_2(CO_3)_3.

Step 7: (g) Sodium Hypobromite

Sodium has a charge of +1, while hypobromite has a charge of -1. To combine these ions to form a neutral compound, we need one sodium ion per hypobromite ion. Thus, the formula is NaBrO.

Key Concepts

Ions and Charges

Atoms form ions when they gain or lose electrons, leading to a net electric charge. Ions can be cations or anions.
Cations are positively charged ions formed when an atom loses one or more electrons. Metals often form cations, like aluminum with a charge of +3.
Anions are negatively charged ions formed when an atom gains electrons. Nonmetals typically form anions, like the hydroxide ion (OH⁻) with a charge of -1.

• Charges are often indicated in chemical notation by superscripts (e.g., Al³⁺, OH⁻).
• The magnitude of the charge is displayed next to the sign indicating whether it is positive or negative.

Understanding ions and their charges is crucial in predicting how elements will interact to form compounds.

Chemical Compounds

Chemical compounds result from the chemical bonding of two or more elements. These compounds can be either ionic or covalent.
*Ionic compounds* are formed when metals transfer electrons to nonmetals, resulting in a bond between a cation and an anion. For example, aluminum hydroxide is an ionic compound.
*Covalent compounds* involve the sharing of electrons between nonmetals. However, the focus here is on ionic compounds.

• Compounds are represented by chemical formulas that indicate the types and numbers of atoms involved.
• Aluminum hydroxide's formula Al(OH) 3 reveals it is made of one aluminum cation and three hydroxide anions.

Each compound has a unique chemical formula that conveys its composition and proportion of the ions involved.

Neutral Compounds

When ions combine to form a compound, the resulting compound is electrically neutral. This means that the total positive charge must balance the total negative charge.
For instance, in aluminum hydroxide, one aluminum ion with a +3 charge balances with three hydroxide ions, each with a -1 charge, resulting in a neutral compound.
In copper(I) oxide, two copper ions, each with a +1 charge, balance one oxide ion with a -2 charge, resulting in Cu 2 O.

• Neutral compounds do not have any net charge.
• Chemical formulas reflect the smallest whole number ratio of ions that achieve neutrality.

Understanding this balance is key to writing correct and meaningful chemical formulas.

Balancing Chemical Equations

Balancing chemical equations is about ensuring that the law of conservation of mass is observed. This means the number of each type of atom is the same on both sides of the equation.
While slightly different from simply writing chemical formulas, it relies on the same principle of neutrality.
Balancing equations ensures that matter is neither created nor destroyed in a chemical reaction. Here is how you generally achieve balance:

• Write the correct formulas for all the reactants and products.
• Adjust coefficients (the numbers in front of the chemical formulas) to ensure that the same number of each atom exists on both sides.
• Check your work by counting the atoms again.

For instance, if writing a reaction involving aluminum hydroxide, ensure that the aluminum, oxygen, and hydrogen atoms are accounted for on both sides of your equation.