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`

Answer

To determine which of the following substances is a strong electrolyte, we need to understand what a strong electrolyte is. A strong electrolyte is a substance that completely dissociates into ions when dissolved in water, allowing it to conduct electricity efficiently.

### Step-by-Step Solution:

1. **Identify the Candidates**: The question likely provides a list of substances. For the sake of this solution, let's assume the candidates are:
- A. Salt (e.g., NaCl)
- B. Calcium Hydroxide (Ca(OH)₂)
- C. Nitric Acid (HNO₃)
- D. Sulfurous Acid (H₂SO₃)
- E. Ammonium Ion (NH₄⁺)

2. **Analyze Each Candidate**:
- **Salt (e.g., NaCl)**: Sodium chloride is a classic example of a strong electrolyte. It completely dissociates into Na⁺ and Cl⁻ ions in solution.
- **Calcium Hydroxide (Ca(OH)₂)**: This is a strong base and can be considered a strong electrolyte, but it is not as completely dissociated in water as NaCl. However, it does dissociate significantly.
- **Nitric Acid (HNO₃)**: This is a strong acid and completely dissociates into H⁺ and NO₃⁻ ions in solution, making it a strong electrolyte.
- **Sulfurous Acid (H₂SO₃)**: This is a weak acid and does not completely dissociate in solution, classifying it as a weak electrolyte.
- **Ammonium Ion (NH₄⁺)**: Ammonium is a weak electrolyte as it does not fully dissociate in solution.

3. **Conclusion**: From the analysis, both Sodium Chloride (Salt), Calcium Hydroxide, and Nitric Acid are strong electrolytes. However, among these, HNO₃ is a well-known strong acid and thus a strong electrolyte.

### Final Answer:
The strong electrolyte among the options is **Nitric Acid (HNO₃)**.