When 1.0 mol of HF is dissolved in 1.0 kg of water, the boiling point of the resulting solution is 100.5 °C. Is HF a strong or weak electrolyte? Explain.

Verified step by step guidance

1. insert step 1: Understand the concept of electrolytes. Strong electrolytes completely dissociate into ions in solution, while weak electrolytes only partially dissociate.
2. insert step 2: Recall the colligative properties of solutions. The boiling point elevation is a colligative property, which depends on the number of solute particles in the solution.
3. insert step 3: Use the boiling point elevation formula: \( \Delta T_b = i \cdot K_b \cdot m \), where \( \Delta T_b \) is the boiling point elevation, \( i \) is the van't Hoff factor, \( K_b \) is the ebullioscopic constant of the solvent, and \( m \) is the molality of the solution.
4. insert step 4: Calculate the boiling point elevation: \( \Delta T_b = 100.5 \degree C - 100.0 \degree C = 0.5 \degree C \).
5. insert step 5: Analyze the van't Hoff factor \( i \). If HF were a strong electrolyte, it would completely dissociate, resulting in a higher \( i \) value and a greater boiling point elevation. The observed \( \Delta T_b \) suggests partial dissociation, indicating HF is a weak electrolyte.

Key Concepts

Electrolytes

Electrolytes are substances that dissociate into ions when dissolved in water, allowing the solution to conduct electricity. They can be classified as strong or weak based on the extent of their ionization. Strong electrolytes completely dissociate into ions, while weak electrolytes only partially dissociate, resulting in fewer ions in solution.

Boiling Point Elevation

Boiling point elevation is a colligative property that describes how the boiling point of a solvent increases when a solute is added. The extent of this elevation depends on the number of solute particles in the solution. In this case, the increase in boiling point from 100 °C to 100.5 °C indicates that the solute (HF) contributes to the solution's overall particle concentration.

HF as an Electrolyte

Hydrofluoric acid (HF) is classified as a weak electrolyte because it only partially ionizes in solution. When HF dissolves in water, it produces a mixture of HF molecules and ions (H⁺ and F⁻), but not all HF molecules dissociate. The observed boiling point elevation suggests that HF does contribute to the solution's ionic strength, but its incomplete dissociation confirms its status as a weak electrolyte.