Problem 24 - Chemistry in 30 days

Question

Calcium carbide reacts with water to produce (a) Ethane (b) Methane (c) Ethylene (d) Acetylene

Step-by-Step Solution

Answer

The product is acetylene, which is option (d).

Step 1: Identify Reactants and Products

The problem involves the reaction of calcium carbide with water. Calcium carbide is denoted as \( \text{CaC}_2 \) and it's known that it reacts with water (\( \text{H}_2\text{O} \)) in particular conditions to form a hydrocarbon, which is the product of interest in this question.

Step 2: Write the Chemical Reaction

The balanced chemical equation for the reaction between calcium carbide (\( \text{CaC}_2 \)) and water (\( \text{H}_2\text{O} \)) is: \[ \text{CaC}_2 + 2\text{H}_2\text{O} \rightarrow \text{C}_2\text{H}_2 + \text{Ca(OH)}_2 \] This indicates that when calcium carbide reacts with water, it produces acetylene (\( \text{C}_2\text{H}_2 \)) and calcium hydroxide (\( \text{Ca(OH)}_2 \)).

Step 3: Identify the Product of Interest

From the balanced chemical equation, the hydrocarbon produced is acetylene (\( \text{C}_2\text{H}_2 \)). This matches option (d) in the provided choices in the exercise.

Key Concepts

Calcium Carbide

Calcium carbide is a chemical compound with the formula \( \text{CaC}_2 \). It is a grayish-black solid commonly used in industrial applications.
One of its most notable characteristics is its reactivity with water. When calcium carbide comes into contact with water, it instigates a chemical reaction leading to the production of acetylene gas.
During this reaction, the carbide ion combines with water molecules to release acetylene.

• Formula: \( \text{CaC}_2 \)
• Appearance: Grayish-black solid
• Main Reaction: Reacts with water to form acetylene

The importance of calcium carbide lies in its historical and practical uses. Before modern techniques came into play, acetylene lamps were a popular source of portable lighting, relying heavily on calcium carbide. In addition, it's still used in some rural areas where electric light isn't readily available.

Acetylene Production

The production of acetylene involves the reaction of calcium carbide with water. This is a classic case of a chemical reaction leading to the formation of a new substance.
Acetylene, represented by the chemical formula \( \text{C}_2\text{H}_2 \), is a colorless gas with a distinct odor. In the presence of the right conditions, calcium carbide and water react to produce acetylene, releasing energy in the process.
The reaction equation is straightforward:

• \( \text{CaC}_2 + 2\text{H}_2\text{O} \rightarrow \text{C}_2\text{H}_2 + \text{Ca(OH)}_2 \)
• Reactants: Calcium carbide and water
• Products: Acetylene and calcium hydroxide

Acetylene has numerous applications in industries today, primarily due to its flammability and high-temperature flame when burned with oxygen. It's widely used in welding and cutting metals and as a building block in chemical synthesis.

Balanced Chemical Equations

Balanced chemical equations are essential in demonstrating how reactants transform into products. In the case of the reaction between calcium carbide and water, balancing the equation ensures that the law of conservation of mass is respected. This law dictates that matter can neither be created nor destroyed, only transformed.
For the equation \( \text{CaC}_2 + 2\text{H}_2\text{O} \rightarrow \text{C}_2\text{H}_2 + \text{Ca(OH)}_2 \), each side of the equation contains the same number of each type of atom:

• Calcium (Ca): 1 on each side
• Carbide and hydrogen atoms are also balanced with 2 carbon atoms and 4 hydrogen atoms in total on each side.

This balance helps chemists predict the quantities of reactants needed and the amounts of products formed. It provides a clear framework for understanding the stoichiometry of chemical reactions, ensuring that calculations are accurate and predictions reliable.