Problem 74 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is not correct? (a) a mixture of \(\mathrm{Ca}(\mathrm{CN})_{2}\) and \(\mathrm{C}\) is known as nitrolim (b) hydrolysis of \(\mathrm{NCl}_{3}\) gives \(\mathrm{NH}_{3}\) and \(\mathrm{HOCl}\) (c) a mixture of \(\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2}\) and \(\mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}\) is known as super phosphate of lime (d) ammonia is used as refrigerant

Step-by-Step Solution

Answer

(c) is not correct.

Step 1: Analyze Option (a)

A mixture of calcium cyanamide \( \mathrm{Ca} (\mathrm{CN})_{2} \) and carbon \( \mathrm{C} \) is indeed known as nitrolim. Option (a) is correct.

Step 2: Analyze Option (b)

When nitrogen trichloride \( \mathrm{NCl}_{3} \) undergoes hydrolysis, it results in ammonia \( \mathrm{NH}_{3} \) and hypochlorous acid \( \mathrm{HOCl} \). Hence, option (b) is correct.

Step 3: Analyze Option (c)

Superphosphate of lime refers to a product that primarily contains calcium dihydrogen phosphate \( \mathrm{Ca}(\mathrm{H}_{2} \mathrm{PO}_{4})_{2} \), but it does not include calcium sulfate \( \mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O} \). Therefore, this description is incorrect, which makes option (c) the incorrect statement.

Step 4: Analyze Option (d)

Ammonia \( \mathrm{NH}_{3} \) is commonly used as a refrigerant due to its efficient heat absorption properties. Therefore, option (d) is correct.

Key Concepts

Nitrolim

Nitrolim is an important chemical often used in agriculture as a nitrogen fertilizer. It is composed of calcium cyanamide (\( \mathrm{Ca} ( \mathrm{CN})_{2} \)) and carbon (\( \mathrm{C} \)). When used as a fertilizer, nitrolim gradually releases its nitrogen content into the soil, providing a steady supply of nutrient to the plants.
It is particularly useful for promoting healthy growth and increasing crop yields.

• Calcium cyanamide reacts slowly in the soil, releasing ammonia which plants can easily absorb.
• This slow release mechanism makes it preferable in regions requiring long-lasting soil nutrient enrichment.
• Nitrolim also helps in controlling certain soil-borne pests and diseases, enhancing overall crop health.

Understanding the composition and uses of nitrolim is essential for students studying inorganic chemistry, as it highlights the application of chemical compounds in real-world scenarios.

Hydrolysis of Nitrogen Trichloride

Nitrogen trichloride (\( \mathrm{NCl}_{3} \)) is a volatile and reactive compound. When it undergoes hydrolysis, it is broken down into two important products: ammonia (\( \mathrm{NH}_{3} \)) and hypochlorous acid (\( \mathrm{HOCl} \)).
This reaction is crucial in understanding various chemical processes and industrial applications.

• Ammonia formed from this process can be further utilized in fertilizers and other chemical syntheses.
• Hypochlorous acid is a powerful disinfectant, often used in sanitation and water treatment.
• The hydrolysis reaction also is exothermic, releasing energy which can influence its surroundings.

Understanding this reaction helps students appreciate the broader applications of inorganic chemistry reactions, both in environmental contexts and industrial settings.

Superphosphate of Lime

Superphosphate of lime is a well-known fertilizer that greatly aids in improving soil fertility. It primarily consists of calcium dihydrogen phosphate \( \mathrm{Ca}( \mathrm{H}_{2} \mathrm{PO}_{4})_{2} \) and does not actually contain calcium sulfate \( \mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O} \). This fertilizer is highly soluble in water, which makes the phosphate available more quickly for plant uptake.

• It facilitates the rapid growth of roots and enhances the overall plant development.
• Superphosphate of lime is particularly beneficial in high-demand crops that need a quick supply of phosphorus.
• Unlike other slower-releasing fertilizers, its high solubility means it is more suited for crops requiring immediate phosphorus availability.

Therefore, not only is it a key subject for chemistry, but understanding its proper composition is important for agricultural practices.

Ammonia as Refrigerant

Ammonia (\( \mathrm{NH}_{3} \)) has been used as a refrigerant for more than a century. Its excellent thermodynamic properties make it a very efficient choice for industrial refrigeration and even some large-scale air conditioning systems. Because ammonia does not contribute to ozone depletion and has negligible global warming potential, it is seen as an environmentally friendly refrigerant option.

• Ammonia's strong latent heat of vaporization means it absorbs a high amount of heat as it changes from liquid to gas, making it very effective in cooling systems.
• Ammonia is cost-effective and more energy-efficient compared to several synthetic refrigerants.
• Despite its benefits, it requires careful handling due to its toxicity and the potential for causing irritation if leaked in high concentrations.

For students, understanding ammonia's role as a refrigerant is crucial as it combines principles of chemistry with practical applications in environmental engineering.