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A cryoscopic measurement gives the molar mass of sodium chloride as 31.80 g mol⁻¹. What is its degree of dissociation? [Atomic masses: Na = 23 g mol⁻¹, Cl = 35.5 g mol⁻¹]

1. 0.58
2. 0.73
3. 0.83
4. 0.92

Correct answer: 0.83

Solution

The degree of dissociation can be calculated by comparing the observed molar mass from the cryoscopic measurement with the expected molar mass of sodium chloride based on its complete dissociation into ions. The calculated degree of dissociation of 0.83 indicates that a significant portion of the sodium chloride dissociates into sodium and chloride ions in solution.

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