Problem 86 - A Complete Resource Book in Chemistry for JEE Main

Question

In the presence of cobalt chloride \(\left(\mathrm{CoCl}_{2}\right)\), bleaching powder decomposes to form (a) \(\mathrm{Cl}_{2} \mathrm{O}\) and \(\mathrm{CaO}\) (b) \(\mathrm{CaCO}_{3}\) and \(\mathrm{O}_{3}\) (c) \(\mathrm{CaCl}_{2}\) and \(\mathrm{O}_{2}\) (d) \(\mathrm{ClO}_{2}\) and \(\mathrm{CaO}\)

Step-by-Step Solution

Answer

The products are \(\text{CaCl}_2\) and \(\text{O}_2\); correct answer is (c).

Step 1: Understanding the reaction

Bleaching powder, or calcium hypochlorite \(\text{Ca(ClO)}_2\), decomposes in the presence of cobalt chloride \(\mathrm{CoCl}_2\) to release oxygen. This step helps identify what gases might be produced.

Step 2: Write the balanced chemical equation

The decomposition of bleaching powder \(\text{Ca(ClO)}_2\) in the presence of a catalyst like \(\mathrm{CoCl}_2\) can be represented as: \[ 2 \text{Ca(ClO)}_2 \rightarrow 2 \text{CaCl}_2 + \text{O}_2 \]This shows the formation of calcium chloride and oxygen.

Step 3: Identify the Products

From the balanced equation, determine the products: calcium chloride \(\mathrm{CaCl}_2\) and oxygen \(\mathrm{O}_2\). These are the substances formed from the decomposition reaction.

Step 4: Choose the correct answer

Compare the given options with the products of the reaction:- Option (c) \(\text{CaCl}_2\) and \(\text{O}_2\) matches the identified products from the balanced equation.Thus, option (c) is the correct answer.

Key Concepts

Bleaching Powder Decomposition

Bleaching powder, also known as calcium hypochlorite, is a chemical compound frequently used for its disinfecting and bleaching properties. It is often represented as \( \text{Ca(ClO)}_2 \). When decomposed, it can release oxygen, which explains part of its effectiveness as a bleach and disinfectant.
During decomposition in the presence of cobalt chloride, the compound breaks down into simpler substances. This process is crucial for applications involving the release of chlorine and oxygen gases.
The decomposition of bleaching powder is a classic example of a chemical reaction where a complex molecule breaks apart to form simpler products.

• The primary components released include various chlorites or chlorates as well as oxygen.
• This breakdown is significantly influenced by environmental factors, such as the presence of a catalyst like cobalt chloride (\( \text{CoCl}_2 \)).
• The end products depend on both the conditions and the specific materials involved in the process.

Catalysis

Catalysis involves a substance that speeds up a chemical reaction without itself undergoing any permanent chemical change. In the decomposition of bleaching powder, cobalt chloride acts as a catalyst. It plays a vital role in facilitating the reaction, allowing it to proceed more efficiently.
In chemical reactions, catalysts provide an alternative reaction pathway with a lower activation energy. This means that the reaction can progress faster and at lower temperatures than it might under normal conditions.

• Cobalt chloride, as used here, can enhance the rate of decomposition by stabilizing intermediates or altering reaction mechanisms.
• It remains unchanged after the reaction, meaning it can continue to facilitate multiple cycles of the reaction without being consumed.
• The use of a catalyst is beneficial in both industrial and laboratory settings, reducing time and resources needed for chemical processes.

Chemical Equation Balancing

Balancing chemical equations is a crucial skill in understanding and describing chemical reactions. It involves ensuring that the number of atoms for each element is equal on both sides of the equation.
For the decomposition reaction of bleaching powder, the balanced equation is:\[ 2 \text{Ca(ClO)}_2 \rightarrow 2 \text{CaCl}_2 + \text{O}_2 \]This equation indicates that two molecules of calcium hypochlorite yield two molecules of calcium chloride and one molecule of oxygen gas.

• Balanced equations comply with the law of conservation of mass, which states that mass is neither created nor destroyed in chemical reactions.
• This process requires counting and equating atoms of each element on both sides of the equation.
• By balancing equations, chemists can predict the amounts of products formed and reactants needed.