Which of the following is not correct ?

Options

A. Ammonia is used as refrigerant.
B. A mixture of `Ca (CN)_(2)` and C is known as nitrolim.
C. A mixture of `Ca(H_(2)PO_(4))_(2)` and `CaSO_(4).2H_(2)O` is known as superphosphate of lime.
D. Hydrolysis of `NCl_(3)` gives `NH_(3)` and `HOCl`.

Explanation

To determine which of the statements is not correct, we will analyze each option one by one.

### Step 1: Analyze the first statement
**Statement:** Ammonia is used as a refrigerant.

**Analysis:**
- Ammonia (NH3) is indeed used as a refrigerant. It is stored as a liquid in refrigeration systems under pressure. When the pressure is released, it evaporates and absorbs heat, making it effective for refrigeration.

**Conclusion:** This statement is **correct**.

### Step 2: Analyze the second statement
**Statement:** A mixture of CaCN2 and C is known as nitro-limb.

**Analysis:**
- Nitro-limb is produced by the reaction of calcium carbide (CaC2) with nitrogen and oxygen. The correct product of this reaction is calcium cyanamide (CaCN2) along with carbon monoxide (CO), not just carbon (C). Therefore, the statement that it is a mixture of CaCN2 and C is misleading.

**Conclusion:** This statement is **not correct**.

### Step 3: Analyze the third statement
**Statement:** A mixture of superphosphate of lime is a mixture of gypsum and monobasic calcium phosphate.

**Analysis:**
- Superphosphate of lime is indeed a mixture that includes gypsum (calcium sulfate) and monobasic calcium phosphate. This aligns with the definition of superphosphate.

**Conclusion:** This statement is **correct**.

### Step 4: Analyze the fourth statement
**Statement:** Hydrolysis of NHCl3 gives NH3 and HOCl.

**Analysis:**
- The hydrolysis of ammonium chloride (NH4Cl) does yield ammonia (NH3) and hypochlorous acid (HOCl). This statement is consistent with the known chemistry of NHCl3.

**Conclusion:** This statement is **correct**.

### Final Conclusion
After analyzing all the statements, the only incorrect statement is the second one.

### Answer:
**The statement that is not correct is option B: A mixture of CaCN2 and C is known as nitro-limb.**

---