Which of the following hydrogen halide is liquid at room temperature ?

Options

A. HF
B. HCl
C. HBr
D. HI

Answer

To determine which hydrogen halide is liquid at room temperature, we need to analyze the properties of the hydrogen halides: HF (hydrogen fluoride), HCl (hydrogen chloride), HBr (hydrogen bromide), and HI (hydrogen iodide).

**Step 1: Identify the hydrogen halides**
- The hydrogen halides in question are HF, HCl, HBr, and HI.

**Step 2: Understand the states of these compounds at room temperature**
- Room temperature is typically around 25°C (298 K).
- HF (hydrogen fluoride) is known to be a liquid at room temperature.
- HCl (hydrogen chloride) is a gas at room temperature.
- HBr (hydrogen bromide) is also a gas at room temperature.
- HI (hydrogen iodide) is a gas at room temperature.

**Step 3: Analyze the intermolecular forces**
- HF exhibits strong hydrogen bonding due to the highly electronegative fluorine atom, which leads to a higher boiling point compared to the others.
- HCl, HBr, and HI have weaker van der Waals forces (dispersion forces) and do not exhibit significant hydrogen bonding.

**Step 4: Conclusion**
- Among the hydrogen halides, HF is the only one that is a liquid at room temperature due to its strong hydrogen bonding.

**Final Answer:**
The hydrogen halide that is liquid at room temperature is HF (hydrogen fluoride).

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