CAN manufacture basics:\nWhich combination of raw materials is required, along with NH3, to produce calcium ammonium nitrate (CAN)?

Introduction / Context:
Calcium ammonium nitrate (CAN) is a granular straight nitrogen fertiliser stabilized with calcium carbonate or limestone to reduce caking and acidity. Understanding the required raw materials clarifies process flows in integrated nitric acid–ammonium nitrate complexes.

Given Data / Assumptions:

• Ammonium nitrate is made from NH3 + HNO3.
• CAN incorporates limestone or dolomite as a conditioner.
• We seek the materials used jointly with NH3.

Concept / Approach:
First, ammonia and nitric acid react exothermically to form ammonium nitrate solution. This solution is then neutralized/conditioned and granulated with finely ground limestone (or dolomite) to produce CAN prills or granules with improved physical properties and less acidifying effect in soil. CO2, H2SO4, KNO3, or NH4Cl are not required for this standard route.

Step-by-Step Solution:

Verification / Alternative check:
Process block diagrams of CAN plants consistently show nitric acid and limestone additions upstream of granulation.

Why Other Options Are Wrong:

• CO2 and H2SO4: unrelated to CAN synthesis.
• HNO3 and NH4Cl: NH4Cl is not part of CAN; it is itself a nitrogen fertiliser.
• CO2 and KNO3: KNO3 is a different fertiliser (potassium nitrate).
• NH3 only: cannot produce CAN without nitric acid and limestone.

Common Pitfalls:
Confusing CAN with calcium nitrate or ammonium sulphate; assuming CO2 neutralization is used instead of limestone conditioning.

Final Answer:
HNO3 and limestone