Problem 36 - A Complete Resource Book in Chemistry for JEE Main

Question

Which one of the following substances is used as a fertilizer? (a) \(\mathrm{Ca}(\mathrm{CN})_{2}\) (b) \(\mathrm{CaSO}_{4}\) (c) \(\mathrm{K}_{2} \mathrm{SO}_{4} \cdot \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3} \cdot 14 \mathrm{H}_{2} \mathrm{O}\) (d) \(\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} \mathrm{H}_{2} \mathrm{O} \cdot 2\left(\mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}\right)\)

Step-by-Step Solution

Answer

Option (d) is the correct answer; it is superphosphate, a phosphorus fertilizer.

Step 1: Identify Fertilizer Components

Fertilizers generally contain components that contribute essential nutrients to plants, notably nitrogen, phosphorus, or potassium.

Step 2: Analyze Option (a)

Option (a) is \( \mathrm{Ca} (\mathrm{CN})_{2} \), known as calcium cyanamide. Calcium cyanamide is used as a fertilizer because it releases nitrogen into the soil.

Step 3: Analyze Option (b)

Option (b) is \( \mathrm{CaSO}_{4} \), known as calcium sulfate or gypsum. It is not typically used as a fertilizer, but rather as a soil conditioner to improve soil structure.

Step 4: Analyze Option (c)

Option (c) is \( \mathrm{K}_{2} \mathrm{SO}_{4} \cdot \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3} \cdot 14 \mathrm{H}_{2} \mathrm{O} \), also known as potash alum. It is not used as a fertilizer.

Step 5: Analyze Option (d)

Option (d) is \( \mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} \mathrm{H}_{2} \mathrm{O} \cdot 2\left(\mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}\right) \), known as superphosphate. This is commonly used as a phosphorus fertilizer.

Step 6: Determine the Correct Answer

Based on the analysis, both options (a) and (d) can act as fertilizers, but superphosphate (option d) is more widely recognized and used in agriculture for its phosphorus content.

Key Concepts

Calcium Cyanamide

Calcium cyanamide, with the chemical formula \( \mathrm{Ca} (\mathrm{CN})_{2} \), is a unique fertilizer with a fascinating role in agriculture. It is primarily utilized for its ability to release nitrogen into the soil as it breaks down. Nitrogen is one of the macronutrients essential for plant growth, primarily supporting leaf growth and overall plant health.

When calcium cyanamide is applied to the soil, a chemical reaction occurs. This reaction converts calcium cyanamide into calcium carbonate and ammonia. The process enriches the soil with nitrogen in a form that plants can easily absorb.

In addition to providing vital nitrogen, calcium cyanamide can also aid in pest control. It acts as a herbicide by reducing the presence of weed seeds in the soil, giving cultivated plants less competition and more resources to thrive. However, handling calcium cyanamide requires care, as it can be irritating and should not be mixed with certain other chemicals.

In summary, calcium cyanamide offers a multi-faceted benefit to agriculture, mainly by enhancing nitrogen levels in the soil and reducing weed competition.

Superphosphate

Superphosphate, known chemically as \( \mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} \mathrm{H}_{2} \mathrm{O} \cdot 2\left(\mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}\right) \), is an essential fertilizer used to bolster phosphorus levels in the soil. Phosphorus is crucial for several aspects of plant development, particularly root development, flower, and fruit production.

Produced by reacting phosphate rocks with sulfuric acid, superphosphate supply plants with a substantial dosage of phosphorus in a form that they can readily absorb. When applied to soil, it dissolves and increases the availability of phosphorus, allowing plants to use it to strengthen their roots and enhance overall growth.

Phosphorus from superphosphates supports energy transfer within plants, aiding in converting other nutrients into usable building blocks. This makes superphosphate a common choice for gardeners and farmers aiming to improve the yield and quality of their crops. Additionally, its ability to work effectively across various soil types makes it versatile in different agricultural settings.

Soil Nutrients

Soil nutrients are the building blocks for plant growth, and understanding them is key to successful agriculture. The primary soil nutrients essential for plant health are nitrogen (N), phosphorus (P), and potassium (K). Each of these macronutrients plays a specific role:

• Nitrogen - Essential for vegetative growth, it supports the development of lush, green foliage.
• Phosphorus - Important for root growth, blooms, and fruit development. It is crucial for energy transfer and photosynthesis.
• Potassium - Enhances the plant's ability to resist disease, stress, and aids in water regulation and enzyme activation.

Besides macronutrients, plants also require micronutrients, though in smaller amounts, such as iron, manganese, zinc, and copper. Micronutrients help support various physiological functions within the plant.

Healthy soil must maintain a balance of these nutrients, as the deficiency or excess of any can lead to reduced plant growth or vitality. Agriculturists often rely on soil tests to assess nutrient levels, tailoring fertilization strategies to bring about the ideal nutrient composition for crop success. Understanding soil nutrient needs enables farmers and gardeners to apply the right type of fertilizer, like calcium cyanamide for nitrogen or superphosphate for phosphorus, thus maintaining a thriving garden or crop.