40 g sodium hydroxide is dissolved in 500 g water. What is the approximate mole fraction of sodium hydroxide?
Answer and explanation
Correct answer: 0.0347
Molar mass of NaOH is 40 g mol⁻¹, so 40 g represents 1.00 mol. Water contributes 500/18 = 27.78 mol. The total number of moles is therefore 1.00 + 27.78 = 28.78 mol. Mole fraction of NaOH is its moles divided by the total moles: 1.00/28.78 = 0.0347, approximately. Option A is too small, while C and D result from using an incorrect total or denominator.
Frequently asked questions
What is the correct answer to this question?
0.0347
Why is this the correct answer?
Molar mass of NaOH is 40 g mol⁻¹, so 40 g represents 1.00 mol. Water contributes 500/18 = 27.78 mol. The total number of moles is therefore 1.00 + 27.78 = 28.78 mol. Mole fraction of NaOH is its moles divided by the total moles: 1.00/28.78 = 0.0347, approximately. Option A is too small, while C and D result from using an incorrect total or denominator.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
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