Problem 57 - A Complete Resource Book in Chemistry for JEE Main

Question

On heating quick lime with coke in an electric furnace, we get (a) \(\mathrm{CaC}_{2}\) (b) \(\mathrm{CaCO}_{3}\) (c) \(\mathrm{CaO}\) (d) \(\mathrm{Ca}\) and \(\mathrm{CO}_{2}\)

Step-by-Step Solution

Answer

The product formed is calcium carbide, \( \mathrm{CaC}_{2} \), so the answer is (a).

Step 1: Understand the Reactants

The reactants in this scenario are quick lime, which is chemically represented as \( \mathrm{CaO} \), and coke, which is a source of carbon, usually as \( \mathrm{C} \). The reaction occurs in an electric furnace, which provides high temperatures necessary for the reaction.

Step 2: Identify Possible Reactions

At high temperatures in an electric furnace, calcium oxide (quick lime) can react with carbon (coke) to form calcium carbide, \( \mathrm{CaC}_{2} \), in a combination process. This is a known reaction where two steps occur: calcium oxide reduces to calcium first, and then this calcium reacts with carbon to form calcium carbide.

Step 3: Write the Balanced Chemical Equation

The reaction between calcium oxide and coke can be represented by the balanced equation: \[ \mathrm{CaO} + 3\mathrm{C} \rightarrow \mathrm{CaC}_{2} + \mathrm{CO} \] This equation demonstrates that calcium carbide (\( \mathrm{CaC}_{2} \)) is produced along with carbon monoxide (\( \mathrm{CO} \)).

Step 4: Evaluate All Given Options

From the balanced equation, the product created by heating quick lime with coke in an electric furnace is calcium carbide, \( \mathrm{CaC}_{2} \). The other options given - \( \mathrm{CaCO}_{3} \), \( \mathrm{CaO} \), and \( \mathrm{Ca} \) and \( \mathrm{CO}_{2} \) - do not correspond to the reaction setup outlined.

Key Concepts

Understanding Chemical Reactions

Chemical reactions are processes where substances, called reactants, are transformed into different substances, known as products. In the context of producing calcium carbide, we start with quick lime (\( \mathrm{CaO} \)) and coke (\( \mathrm{C} \)) as reactants. When these two substances are combined in an electric furnace, they undergo a chemical reaction.

The essence of any chemical reaction lies in the breaking and forming of chemical bonds. For the calcium carbide production reaction, this transformation allows new compounds to form.

• Calcium oxide provides the calcium needed for the final product, while carbon from coke is essential for forming calcium carbide.
• During this process, atoms are rearranged but not created or destroyed, adhering to the law of conservation of mass.

Understanding the substances involved and how they interact is crucial to predict the products of such chemical reactions accurately.

Role of High Temperature Reactions

High temperature reactions involve heating substances to initiate or accelerate chemical changes. These reactions are essential in industries for producing compounds like calcium carbide.

In the given scenario, heating is performed using an electric furnace, which ensures the high temperatures required for the reaction between calcium oxide (quick lime) and carbon (coke).

• High temperatures supply the energy necessary to break chemical bonds in the reactants, a prerequisite for forming new compounds.
• This additional energy permits the reactants to collide more often and with sufficient energy to overcome the activation energy barrier, leading to successful reactions.
• Only at such high temperatures does calcium oxide reduce to calcium and react with carbon to form calcium carbide.

The use of high temperatures is a key factor that can significantly influence the outcome of a chemical reaction by altering the rates and pathways of reactions.

Writing Balanced Chemical Equations

Balanced chemical equations are fundamental to understanding and representing chemical reactions accurately. They show how the quantities of reactants and products are related, ensuring that the law of conservation of mass is respected.

For the reaction between quick lime and coke in producing calcium carbide, the balanced chemical equation is:

\[ \mathrm{CaO} + 3\mathrm{C} \rightarrow \mathrm{CaC}_{2} + \mathrm{CO} \]

• Each element in the reaction must have the same number of atoms on both sides of the equation. This balance confirms that no atoms are lost in the process.
• The equation informs us that one molecule of calcium oxide reacts with three molecules of carbon to produce one molecule of calcium carbide and one molecule of carbon monoxide.
• Balanced equations provide not only the types of substances involved but also the stoichiometry, or the quantitative relationships between them.

Understanding and using balanced chemical equations are crucial for predicting the yields and components of any chemical reaction accurately.