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) \(\mathrm{CaSO}_{4}+\mathrm{CaO}^{2}\) (c) \(\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}+2 \mathrm{CaSO}_{4}\) (d) \(\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} \mathrm{H}_{2} \mathrm{O}+2\left(\mathrm{CaSO}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}\right)\)

Step-by-Step Solution

Answer

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

Step 1: Define Calcium Superphosphate

Calcium superphosphate is a fertilizer product made primarily of calcium dihydrogen phosphate, which is \( \text{Ca(H}_2\text{PO}_4)_2 \). It is commonly produced by treating phosphate rock with sulfuric acid.

Step 2: Analyze Option (a)

Option (a) is \( \text{Ca(H}_2\text{PO}_4)_2 \cdot \text{H}_2\text{O} + \text{CaSO}_4 \). This option includes calcium dihydrogen phosphate, which matches the primary component of calcium superphosphate, with added gypsum (CaSO4).

Step 3: Analyze Option (b)

Option (b) is \( \text{CaSO}_4 + \text{CaO}^2 \). This formula does not contain any calcium dihydrogen phosphate (\( \text{Ca(H}_2\text{PO}_4)_2 \)) and therefore cannot be calcium superphosphate.

Step 4: Analyze Option (c)

Option (c) is \( \text{Ca}_3(\text{PO}_4)_2 + 2 \text{CaSO}_4 \). This formula is typical of a different phosphate called triple superphosphate, not calcium superphosphate.

Step 5: Analyze Option (d)

Option (d) is \( \text{Ca(H}_2\text{PO}_4)_2 \cdot \text{H}_2\text{O} + 2(\text{CaSO}_2 \cdot 2 \text{H}_2\text{O}) \). While this contains calcium dihydrogen phosphate, the formula for the additional component (CaSO2) does not represent a substance typically included in calcium superphosphate.

Step 6: Choose the Correct Option

Among the given options, only option (a) includes the essential ingredient, calcium dihydrogen phosphate, which is necessary for a compound to be classified as calcium superphosphate.

Key Concepts

Calcium Dihydrogen Phosphate

Calcium dihydrogen phosphate is a crucial compound within the world of fertilizers. Chemically represented as \( \text{Ca(H}_2\text{PO}_4)_2 \), it is primarily used in agriculture due to its high phosphorus content.
Phosphorus is a key nutrient essential for plant growth. Unlike pure phosphate stones, calcium dihydrogen phosphate is water-soluble, making it readily available for plant uptake.

• Improves root development and increases blooming.
• Enhances the ability of plants to absorb and utilize other nutrients.

Its solubility and efficiency in delivering essential phosphorus make calcium dihydrogen phosphate the main component in calcium superphosphate fertilizers, providing a steady source of this vital nutrient to the soil.

Fertilizer Production

Fertilizer production is a process dedicated to enhancing the nutrient profile of soil. This involves chemical reactions that transform raw materials into solutions that can be easily absorbed by plants.
One of the primary methods in fertilizer production is the treatment of phosphate rock with sulfuric acid. This chemical reaction results in the formation of calcium dihydrogen phosphate, which is fundamental in producing calcium superphosphate.

• The calcium superphosphate production process secures high levels of phosphorus.
• It potentially includes the addition of gypsum (CaSO4) to provide more calcium content.

By producing fertilizers like calcium superphosphate, agricultural efficiency and crop yields can improve significantly.

Phosphate Rock

Phosphate rock is a type of mineral that naturally contains a high concentration of phosphates. It is a primary source of phosphorus for agricultural fertilizers.
This rock is mined from the earth and plays a vital role in the production of phosphate fertilizers like calcium superphosphate.

• Is a non-renewable resource, hence careful management is essential.
• The quality and phosphorus content can vary depending on the source.

To convert phosphate rock into usable calcium dihydrogen phosphate, it is dissolved in sulfuric acid, triggering a chemical reaction that separates out the needed phosphate compounds. This process is the cornerstone of transforming raw mineral into plant-accessible fertilizer.

Sulfuric Acid

Sulfuric acid is a powerful chemical compound with the formula \( \text{H}_2\text{SO}_4 \). It plays a critical role in the chemical processes used to produce fertilizers like calcium superphosphate.
When phosphate rock is treated with sulfuric acid, the result is a chemical reaction that produces calcium dihydrogen phosphate along with gypsum as a byproduct.

• This reaction is essential for making the phosphorus content of phosphate rock available to plants.
• Used in numerous other industrial processes beyond fertilizer production.

The effectiveness of sulfuric acid in dissolving phosphate rocks and facilitating the extraction of phosphorus compounds underscores its importance in agriculture and industry.