Correct answer: (2)
CaCN₂ + Graphite.
Here is some information regarding Nitrolim,
Nitrolim (also known as nitrolime or lime nitrogen) is a nitrogenous fertilizer prepared by the cyanamide process. It is produced by passing nitrogen gas over heated calcium carbide (CaC₂) at high temperature (around 1000–1100°C).
The reaction is:
CaC₂ + N₂ → CaCN₂ + C (where C is carbon in the form of graphite).
The product is a mixture of calcium cyanamide (CaCN₂, the main nitrogen-containing compound) and free graphite (carbon). Calcium cyanamide itself has the formula CaCN₂ (or often written as CaNCN to emphasize the cyanamide ion [N=C=N]²⁻). The presence of graphite helps prevent the material from becoming sticky or caking during storage and handling.
Commercial nitrolim typically contains about 20–25% nitrogen, and it is used as a fertilizer because it slowly hydrolyzes in soil to release ammonia:
CaCN₂ + 3H₂O → CaCO₃ + 2NH₃.
Here is an another question from Group 15elements…
(Q): Ammonia gas is dried over
- Quick lime
- Conc. H₂SO₄
- P₂O₅
- CaCl₂
Correct answer: 1) Quick lime
Ammonia (NH₃) is a basic gas, so the drying agent must not react chemically with it while effectively removing moisture.
Quick lime (CaO, calcium oxide) is the most suitable and commonly used drying agent for ammonia gas in laboratory preparations.
Quick lime is strongly basic and absorbs water to form slaked lime:
CaO + H₂O → Ca(OH)₂
Since both CaO and NH₃ are basic in nature, there is no acid-base reaction between them—ammonia passes through unchanged. This makes quick lime (or sometimes soda lime, a mixture of CaO and NaOH) ideal for drying ammonia.
The other options are unsuitable for the following reasons:
- 2) Conc. H₂SO₄: Strong acid; reacts vigorously with basic NH₃ to form ammonium sulphate:
- 2NH₃ + H₂SO₄ → (NH₄)₂SO₄
- 3) P₂O₅: Powerful dehydrating agent, but reacts with ammonia to form ammonium phosphates.
- 4) CaCl₂: Hygroscopic and absorbs water well, but forms addition complexes with ammonia (e.g., CaCl₂·8NH₃) and reacts exothermically, so it cannot be used for drying of ammonia.