Identify the fertiliser grade:\nA nitrogenous fertiliser contains about 20% nitrogen by mass. Which product best matches this analysis?

Introduction / Context:
Fertiliser labeling specifies the mass percentage of nutrients, especially nitrogen in nitrogenous products. Being able to match an assay (e.g., ~20% N) to a likely product is a basic competency in agronomy and process operations. This item asks which common fertiliser aligns with an N analysis close to 20%.

Given Data / Assumptions:

• Target nitrogen content ≈ 20% by mass.
• We compare against typical specification values for standard fertilisers.
• Minor regional formulation variations are ignored; use nominal textbook values.

Concept / Approach:
Typical nitrogen contents are: urea ≈ 46% N, ammonium nitrate ≈ 33–35% N, ammonium chloride ≈ 25–26% N, calcium ammonium nitrate (solid) ≈ 26–28% N, and ammonium sulphate ≈ 21% N. Of these, ammonium sulphate most closely matches the stated ~20% N content. Therefore it is the best match among the options provided.

Step-by-Step Solution:

Verification / Alternative check:
Product datasheets and fertiliser handbooks report ammonium sulphate grades around 20–21% N, confirming the match.

Why Other Options Are Wrong:

• Ammonium nitrate: typically ~33–35% N.
• Calcium ammonium nitrate: usually ~26–28% N (solid grade).
• Urea: ~46% N, far above 20%.
• Ammonium chloride: ~25–26% N, not ~20%.

Common Pitfalls:
Assuming CAN could be formulated as low as 20% N (standard solid grades are higher); confusing mass percentages with nutrient oxide equivalents used in NPK labels for P and K.

Final Answer:
Ammonium sulphate