Problem 44 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is calcium superphosphate? (a) \(\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} \mathrm{H}_{2} \mathrm{O}+\mathrm{CaSO}_{4}\) (b) \(\mathrm{CaSO}_{4}+\mathrm{CaO}\) (c) \(\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}+2 \mathrm{CaSO}_{4}\) (d) \(\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} \mathrm{H}_{2} \mathrm{O}+2\left(\mathrm{CaSO}_{2}-2 \mathrm{H}_{2} \mathrm{O}\right)\)

Step-by-Step Solution

Answer

The correct answer is (a) \(\text{Ca(H}_2 \text{PO}_4\text{)}_2\cdot \text{H}_2\text{O} + \text{CaSO}_4\).

Step 1: Understanding Superphosphate Composition

Superphosphate is a mixture primarily containing monocalcium phosphate. Its chemical expression can often be represented as \( \text{Ca(H}_2 \text{PO}_4\text{)}_2\cdot \text{H}_2\text{O} \). It may also be mixed with calcium sulfate.

Step 2: Analyze Each Option

Evaluate each compound option to see if it matches the characteristics of calcium superphosphate:(a) \(\text{Ca(H}_2\text{PO}_4\text{)}_2\cdot \text{H}_2\text{O} + \text{CaSO}_4\)(b) \(\text{CaSO}_4 + \text{CaO}\)(c) \(\text{Ca}_3\text{(PO}_4\text{)}_2 + 2\text{CaSO}_4\)(d) \(\text{Ca(H}_2\text{PO}_4\text{)}_2\cdot \text{H}_2\text{O} + 2(\text{CaSO}_2 - 2\text{H}_2\text{O})\)

Step 3: Identify Calcium Superphosphate

Review the choices with the characteristics identified in Step 1:- Option (a) contains \(\text{Ca(H}_2\text{PO}_4\text{)}_2\cdot \text{H}_2\text{O} + \text{CaSO}_4\), which matches calcium superphosphate composition.- Option (b) contains only calcium sulfate and oxide, not matching.- Option (c) contains tricalcium phosphate and calcium sulfate, not matching.- Option (d) contains monocalcium phosphate but incorrect amounts, not matching.

Step 4: Select the Correct Answer

Based on this analysis, option (a) \(\text{Ca(H}_2\text{PO}_4\text{)}_2\cdot \text{H}_2\text{O} + \text{CaSO}_4\) correctly represents calcium superphosphate.

Key Concepts

Monocalcium Phosphate

Monocalcium phosphate is a notable compound in the world of fertilizers due to its role in calcium superphosphate. This compound is represented by the formula \(\text{Ca(H}_2\text{PO}_4\text{)}_2\). It is a primary ingredient in many fertilizers, especially those meant to supply essential nutrients like phosphorus and calcium to plants.

Monocalcium phosphate is highly soluble in water, which is advantageous because it allows plants to easily absorb the nutrients from the soil.

• This compound provides both calcium and phosphorus, both essential for plant health.
• Phosphorus is crucial for energy transfer and photosynthesis.
• Calcium plays a key role in cell wall structure and signal translocation.

In the context of calcium superphosphate, monocalcium phosphate works in tandem with calcium sulfate to enrich the soil, leading to healthier and faster-growing crops. This makes monocalcium phosphate an invaluable component in agriculture, particularly in regions where soil can be deficient in these crucial elements.

Chemical Composition

Understanding chemical composition is essential in identifying calcium superphosphate. Each component in a chemical formula plays a specific role and contributes to a substance's properties. Calcium superphosphate is a mixture of monocalcium phosphate and calcium sulfate.

A quick look at its composition reveals:

• Monocalcium phosphate, \(\text{Ca(H}_2\text{PO}_4\text{)}_2\), the component that provides phosphorus.
• Calcium sulfate, \(\text{CaSO}_4\), which is more than just filler—it enhances the stability and distribution of the phosphate.

These compounds together form a harmonious blend that efficiently delivers crucial nutrients to plants. In chemical terms, calcium superphosphate exploits the balance between soluble phosphorus and calcium to ensure plant roots can uptake nutrients easily.

The presence of calcium sulfate in the mix also plays a vital role. It helps in maintaining the soil structure by improving its porosity and drainage capabilities. This chemical combination is not random but carefully calculated to optimize agricultural productivity.

Fertilizers

Fertilizers are compounds that are added to soil to provide essential nutrients for plant growth. Among these, phosphorus-based fertilizers like calcium superphosphate dominate due to their critical role in agricultural productivity.

The primary function of fertilizers is to supplement the soil with necessary nutrients that might not naturally occur in sufficient quantities. For fertilizers:

• Nutrients must be easily accessible to plants, which is why solubility is a key factor.
• They work to improve the overall quality and yield of crops.
• They assist in overcoming deficiencies in natural soil.

Calcium superphosphate stands out among phosphorus fertilizers as it supplies both calcium and phosphorus. Its application is especially useful in enriching crop soil where these elements are deficient.

By improving soil fertility, fertilizers like calcium superphosphate encourage stronger plant growth, better resistance to diseases, and ultimately, higher agricultural productivity. They are indispensable in modern agriculture, contributing to sustainable food production and security.