Problem 70 - Chemistry The Central Science In Si Units

Question

Give the names and charges of the cation and anion in each of the following compounds: (a) CuS, (b) \(\mathrm{Ag}_{2} \mathrm{SO}_{4}\), (c) \(\mathrm{Al}\left(\mathrm{ClO}_{3}\right)_{3}\), (d) \(\mathrm{Co}(\mathrm{OH})_{2}\), (e) \(\mathrm{PbCO}_{3}\).

Step-by-Step Solution

Answer

CuS: Cu²⁺ and S²⁻; Ag₂SO₄: Ag⁺ and SO₄²⁻; Al(ClO₃)₃: Al³⁺ and ClO₃⁻; Co(OH)₂: Co²⁺ and OH⁻; PbCO₃: Pb²⁺ and CO₃²⁻.

Step 1: Identify the Cation and Anion in CuS

The compound CuS consists of copper (Cu) and sulfur (S). Copper as a cation is denoted as Cu and has a charge of +2, forming Cu²⁺. Sulfur forms the anion sulfide with a charge of -2, denoted as S²⁻.

Step 2: Identify the Cation and Anion in Ag₂SO₄

The compound Ag₂SO₄ includes silver (Ag) and the sulfate group (SO₄). Silver's cation is Ag⁺ (charge of +1). The sulfate group, which is the anion, has a charge of -2, denoted as SO₄²⁻.

Step 3: Identify the Cation and Anion in Al(ClO₃)₃

Al(ClO₃)₃ is composed of aluminum (Al) and the chlorate group (ClO₃). Aluminum forms a cation with a +3 charge, denoted as Al³⁺. The chlorate group acts as the anion and carries a charge of -1, denoted as ClO₃⁻.

Step 4: Identify the Cation and Anion in Co(OH)₂

Co(OH)₂ consists of cobalt (Co) and the hydroxide group (OH). Cobalt in this compound has a +2 charge, written as Co²⁺. The hydroxide group is the anion and has a charge of -1, represented as OH⁻.

Step 5: Identify the Cation and Anion in PbCO₃

PbCO₃ contains lead (Pb) and the carbonate group (CO₃). Lead forms a cation with a +2 charge, expressed as Pb²⁺. The carbonate group serves as the anion with a -2 charge, symbolized as CO₃²⁻.

Key Concepts

Cation and Anion Identification

Understanding the concept of cations and anions is fundamental in chemistry, especially when dealing with ionic compounds. These compounds are formed when atoms or groups of atoms gain or lose electrons, becoming charged particles known as ions.

• Cation: This is a positively charged ion. Atoms become cations by losing one or more electrons. For instance, copper (Cu) in the compound CuS loses two electrons, forming a cation with a charge of +2, denoted as Cu²⁺.


• Anion: An anion is a negatively charged ion, formed when an atom gains electrons. Sulfur (S) in CuS, for example, gains two electrons to become sulfide with a charge of -2, noted as S²⁻.

By identifying cations and anions, you can better understand the composition and behavior of an ionic compound, allowing you to predict its properties and reactions.

Chemical Formulas

Chemical formulas provide a snapshot of the elements present in a compound and their respective quantities. They offer a simple way to express complex chemical concepts in a compact form.

• Writing Formulas: In a chemical formula, the elements are represented by their chemical symbols, and the number of each type of atom is indicated by a subscript. For example, in the sulfate group \( ext{SO}_{4}\), the subscript '4' signifies four oxygen atoms bonded with one sulfur atom.


• Comprehending Compounds: For instance, the formula \( ext{Ag}_{2} ext{SO}_{4}\) reveals that the compound is made of 2 silver atoms and 1 sulfate group. This representation helps chemists understand how the elements interact within the compound.

Interpreting chemical formulas is key to predicting chemical bonds and reactions, facilitating a deeper comprehension of chemical processes.

Chemical Charges

The concept of chemical charges is pivotal for understanding how atoms and ions interact in compounds. Charges arise from the transfer or sharing of electrons due to differences in electronegativity.

• Determining Charge: Chemical charges can be determined based on electron gain or loss. Silver (Ag) loses one electron to have a charge of +1, whereas sulfate (SO₄) gains two electrons, resulting in a charge of -2.


• Charge Balance: In ionic compounds, the total positive charge and negative charge should balance each other to create a neutral compound. For Co(OH)₂, cobalt Co²⁺ and two hydroxide ions OH⁻ work together to nullify the overall charge to zero.

Understanding chemical charges is essential for predicting the resulting structure and stability of ionic compounds, as well as their potential chemical reactions.