Problem 4 - Chemistry: Principles and Reactions

Question

Write a balanced equation to represent the roasting of copper(I) sulfide to form "blister copper"

Step-by-Step Solution

Answer

Answer: Cu2S (s) + O2 (g) ⟶ 2 Cu (s) + SO2 (g)

Step 1: Write the unbalanced chemical equation

First, we need to write the unbalanced equation representing the process: Cu2S (s) + O2 (g) ⟶ Cu (s) + SO2 (g)

Step 2: Count the elements on both sides

In the unbalanced equation we see that there are: Left-hand side (reactants): 2 Cu, 1 S, 2 O Right-hand side (products): 1 Cu, 1 S, 2 O

Step 3: Balance the elements

To make sure that the numbers of atoms of each element are equal on both sides, we will balance the equation by adjusting the stoichiometric coefficients (the numbers in front of the compounds). First, we need to balance the copper (Cu) atoms. Since there are 2 Cu atoms in Cu2S and only 1 Cu atom in Cu, we need to multiply the Cu on the right-hand side by 2: Cu2S (s) + O2 (g) ⟶ 2 Cu (s) + SO2 (g) Now, the equation reads: Left-hand side: 2 Cu, 1 S, 2 O Right-hand side: 2 Cu, 1 S, 2 O The balanced equation is: Cu2S (s) + O2 (g) ⟶ 2 Cu (s) + SO2 (g)

Key Concepts

Roasting Process in Metallurgy

Roasting is a crucial step in metallurgy, particularly for the extraction of metals from their ores. It involves heating the ore in the presence of oxygen. This changes its chemical composition by oxidizing it. Roasting is commonly used to transform sulfide ores into oxides. This is important because oxides are more easily reduced to pure metals.

During roasting, the temperatures must be controlled carefully. The goal is to drive off impurities without physically melting the ore.

• The process often produces sulfur dioxide gas, especially when sulfide ores are involved.
• Roasting is an important preparatory step before reduction.
• It enhances the efficiency of metal extraction.

In the roasting reaction for copper(I) sulfide, it is combined with oxygen to form copper and sulfur dioxide. This prepares the copper for a final purification step, resulting in what's known as "blister copper." This term comes from the blister-like appearance caused by escaping sulfur dioxide gas.

Copper(I) Sulfide

Copper(I) sulfide is a chemical compound represented by the formula \( \text{Cu}_2\text{S} \). It's a black, crystalline solid naturally occurring as the mineral chalcocite.

Copper(I) sulfide is one of many copper sulfide minerals. It plays a vital role in the production of copper metal.

• Chalcocite is valuable due to its high copper content.
• It is primarily used in the mining industry.
• Copper(I) sulfide undergoes a roasting process to be converted into copper metal.

Understanding the properties of \( \text{Cu}_2\text{S} \) is critical for processing ores in metallurgy. It helps predict how this compound will behave during extraction processes, ensuring its efficient transformation into usable metal. Chalcocite itself occurs in an anoxic environment, making it ideal for mining in regions with little oxygen exposure.

Stoichiometry

Stoichiometry is a branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It is essential for balancing chemical equations. Understanding stoichiometry allows you to accurately predict the amounts needed for the reaction and the amounts of products formed.

When balancing a chemical equation, follow these steps:

• Write down the unbalanced equation.
• Count the atoms of each element on both sides of the equation.
• Adjust the coefficients to balance the atoms on both sides.

In the case of copper(I) sulfide roasting, the unbalanced equation \( \text{Cu}_2\text{S} (s) + \text{O}_2 (g) \rightarrow \text{Cu} (s) + \text{SO}_2 (g) \) had more copper atoms on the left than on the right. Balancing it involved increasing the number of copper atoms on the product side to two, resulting in the equation: \[ \text{Cu}_2\text{S} (s) + \text{O}_2 (g) \rightarrow 2 \text{Cu} (s) + \text{SO}_2 (g) \]
Stoichiometry ensures the law of conservation of mass is respected. This means all atoms present in the reactants must be accounted for in the products. Mastery of stoichiometry is fundamental for anyone studying or working in a field related to chemistry.