If a solute completely dissociates into three ions in solution, how will its apparent molar mass compare with its true molar mass?
Answer and explanation
Correct answer: One-third
Complete dissociation of one formula unit into three ions makes the van’t Hoff factor i = 3, assuming ideal complete dissociation and negligible ion pairing. Since the apparent molar mass obtained from a colligative property is M_apparent = M_true/i, it becomes M_true/3. Therefore, the apparent molar mass is one-third of the true molar mass. The increased particle count makes the colligative effect three times larger.
Frequently asked questions
What is the correct answer to this question?
One-third
Why is this the correct answer?
Complete dissociation of one formula unit into three ions makes the van’t Hoff factor i = 3, assuming ideal complete dissociation and negligible ion pairing. Since the apparent molar mass obtained from a colligative property is M_apparent = M_true/i, it becomes M_true/3. Therefore, the apparent molar mass is one-third of the true molar mass. The increased particle count makes the colligative effect three times larger.
Which subject and chapter does this question cover?
This is a Class 12 Chemistry question. Chapter: Chapter 01: Solutions. Topic: 7: Abnormal Molecular Mass.
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