A chemical widely used as a fertilizer is?

Analysis of the Question

The question asks to identify a chemical compound from the given list that is commonly used as a fertilizer in agriculture.

Concept Explanation

Fertilizers are substances added to soil to provide essential nutrients (like Nitrogen, Phosphorus, and Potassium) to plants to improve their growth and yield.

• Nitrogen-based fertilizers are particularly important for leafy growth.
• Nitrochalk is a common commercial fertilizer. It is a mixture of ammonium nitrate ($NH_4NO_3$) and calcium carbonate ($CaCO_3$). The calcium carbonate is added to neutralize the acidity of the ammonium nitrate, making it safer for soil application.

Let's look at the other options:

• Galena ($PbS$): This is the primary ore of lead. It is not used as a fertilizer.
• Bauxite ($Al_2O_3 \cdot 2H_2O$): This is the primary ore of aluminium. It is used in the production of aluminium metal, not as a fertilizer.
• Emerald: This is a gemstone (a variety of the mineral beryl). It is used in jewelry and has no agricultural application as a fertilizer.

Step-by-Step Solution

1. Evaluate the options: We eliminate Galena (lead ore), Bauxite (aluminium ore), and Emerald (gemstone) because they are industrial minerals or precious stones, not agricultural nutrients.
2. Analyze Nitrochalk: Nitrochalk provides nitrogen, which is a primary macronutrient for plants. It is specifically formulated for agricultural use to ensure the soil pH remains balanced while providing the necessary nitrogen.
3. Conclusion: Among the choices provided, Nitrochalk is the only substance recognized as a chemical fertilizer.

Exam Strategy Tip

When you see questions about "common chemicals" in JAMB Chemistry, try to categorize them by their industrial use. If you see an option that sounds like a rock or an ore (like Bauxite or Galena), it is rarely a fertilizer. Look for compounds containing Nitrogen ($N$), Phosphorus ($P$), or Potassium ($K$), as these are the "big three" elements in fertilizers.