Question

Bleaching powder loses its powder on keeping for a long time because: (a) It absorbs moisture (b) It changes into calcium chloride and calcium chlorate (c) It changes into calcium hypochlorate (d) It changes into calcium chloride and calcium hydroxide

Short answer

(d) It changes into calcium chloride and calcium hydroxide.

Step-by-step solution

Understanding Bleaching Powder Composition

Bleaching powder primarily consists of calcium oxychloride, with the chemical formula \( Ca(OCl)_2 \). It is used as a disinfectant and bleaching agent in various applications.

Analyzing Possible Reactions

When exposed to the atmosphere, bleaching powder absorbs moisture and can undergo a reaction leading to its deterioration. We need to determine which chemical changes are plausible based on the options.

Evaluating Option A

Option (a) states that bleaching powder loses its power because it absorbs moisture. While it is true that bleaching powder absorbs moisture, this alone does not account for its loss of effectiveness as a bleaching agent.

Evaluating Option B

Option (b) indicates a change into calcium chloride (\( CaCl_2 \)) and calcium chlorate (\( Ca(ClO_3)_2 \)). This reaction is inconsistent under typical environmental conditions.

Evaluating Option C

Option (c) suggests that bleaching powder changes into calcium hypochlorate. However, this is unlikely as calcium hypochlorate is not a typical decomposition product.

Evaluating Option D

Option (d) signifies that bleaching powder changes into calcium chloride and calcium hydroxide upon prolonged exposure. This is consistent with what actually occurs: \( Ca(OCl)_2 \) reacts with carbon dioxide and moisture, forming \( CaCl_2 \) and \( Ca(OH)_2 \).

Conclusion Based on Analysis

Based on the analysis and typical reactions of bleaching powder, option (d) is the most plausible explanation for its loss of power over time.

Key concepts

Calcium Oxychloride

Calcium oxychloride is often referred to as bleaching powder. It's a compound with the formula \( Ca(OCl)_2 \). This substance is widely used for disinfecting water and bleaching because of its strong oxidizing properties.

When used, the decomposition of calcium oxychloride releases active chlorine. This chlorine, in turn, is what performs the bleaching or disinfecting action. Over time and with exposure to moisture and carbon dioxide in the air, calcium oxychloride can decompose, leading to a loss of its effective properties.

In day-to-day usage, understanding the composition of bleaching powder is crucial. It's also essential to store it properly to prevent its premature decomposition.

• Consists primarily of \( Ca(OCl)_2 \)
• Acts as a strong oxidizer
• Releases active chlorine for its cleansing effects
• Decomposes under exposure, leading to reduced efficacy

Chemical Reaction Analysis

When analysing chemical reactions—like those involving bleaching powder—it is essential to understand the environmental conditions affecting the reaction. Exposure to elements such as moisture and carbon dioxide is significant. These can alter the composition and effectiveness of compounds like calcium oxychloride.

For example, when bleaching powder comes into contact with moisture and atmospheric carbon dioxide, it decomposes into calcium chloride \( CaCl_2 \) and calcium hydroxide \( Ca(OH)_2 \).

This transformation describes the reaction deeper:

• Initial compound: \( Ca(OCl)_2 \)
• Moisture aids the breakdown process
• Products of the reaction: \( CaCl_2 \) (calcium chloride) and \( Ca(OH)_2 \) (calcium hydroxide)

This kind of analysis helps predict the stability and longevity of chemical compounds in varying environments.

Environmental Effects on Compounds

The environment plays a critical role in the stability and reactivity of chemical compounds. For compounds like calcium oxychloride, environmental effects can significantly influence their efficacy and decomposition rate.

Key environmental factors include:

• Moisture: Accelerates the degradation process by facilitating chemical reactions.
• Carbon dioxide: Reacts with the compound to produce different end products, altering the original substance.

Understanding these environmental influences helps in anticipating how and when compounds will change. This kind of knowledge is crucial for determining how long materials like bleaching powder will remain effective under different conditions.