A solution has 25 total moles and a solute mole fraction of 0.16. How many moles of solute are present?
Answer and explanation
Correct answer: 4 mol
The governing relation is the definition of mole fraction: x_solute = n_solute/n_total. Rearranging gives n_solute = x_solute × n_total. Substituting the data, n_solute = 0.16 × 25 = 4 mol. Therefore, option C is correct. The total of 25 mol includes both solute and solvent, so the calculated solute amount must be less than 25 mol, which it is. As a check, 4/25 = 0.16. If the amount were 2 mol, the fraction would be 0.08; for 3 mol it would be 0.12; and for 5 mol it would be 0.20. Thus the distractors do not satisfy the stated mole fraction.
Frequently asked questions
What is the correct answer to this question?
4 mol
Why is this the correct answer?
The governing relation is the definition of mole fraction: x_solute = n_solute/n_total. Rearranging gives n_solute = x_solute × n_total. Substituting the data, n_solute = 0.16 × 25 = 4 mol. Therefore, option C is correct. The total of 25 mol includes both solute and solvent, so the calculated solute amount must be less than 25 mol, which it is. As a check, 4/25 = 0.16. If the amount were 2 mol, the fraction would be 0.08; for 3 mol it would be 0.12; and for 5 mol it would be 0.20. Thus the distractors do not satisfy the stated mole fraction.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
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