Which of the following is a strong electrolyte ?

Options

A. `Ca(NO_(3))_(2)`
B. `HCN`
C. `H_(2)SO_(3)`
D. `NH_(4)OH`

Explanation

To determine which of the given options is a strong electrolyte, we first need to understand the definition and characteristics of strong electrolytes.

### Step-by-Step Solution:

1. **Definition of Strong Electrolytes**:
- Strong electrolytes are substances that completely dissociate into ions when dissolved in water. This means that they exist entirely in ionic form in solution, leading to high electrical conductivity.

2. **Identify the Options**:
- Let's consider the options provided (though not explicitly listed in the question, we can assume common examples).
- Common examples of strong electrolytes include:
- Calcium nitrate (Ca(NO3)2)
- Sodium chloride (NaCl)
- Hydrochloric acid (HCl)
- Weak electrolytes include:
- Hydrocyanic acid (HCN)
- Sulfurous acid (H2SO3)
- Ammonium hydroxide (NH4OH)

3. **Analyzing Each Option**:
- **Ca(NO3)2 (Calcium Nitrate)**: This is a strong electrolyte as it completely dissociates into Ca²⁺ and 2 NO3⁻ ions in solution.
- **HCN (Hydrocyanic Acid)**: This is a weak acid and does not completely dissociate in solution. It establishes an equilibrium between the undissociated HCN and the ions.
- **H2SO3 (Sulfurous Acid)**: This is also a weak acid and does not completely dissociate, similar to HCN.
- **NH4OH (Ammonium Hydroxide)**: This is a weak base and does not completely dissociate in solution, establishing an equilibrium.

4. **Conclusion**:
- Among the options analyzed, **Ca(NO3)2** is the only strong electrolyte as it completely dissociates into ions in solution. The other options (HCN, H2SO3, and NH4OH) are weak electrolytes as they do not fully dissociate.

### Final Answer:
**Ca(NO3)2 is a strong electrolyte.**