The mole fraction of a solute in 2·0 molal aqueous solution is :
Show Hint
- 1·87
- 0·347
- 0·0347
- 0·00347
The Correct Option is C
Solution and Explanation
Step 1: Read the molality
A 2.0 molal solution has 2.0 mol of solute in 1 kg of water. 1 kg of water is 1000 g.
Step 2: Find the moles of water
Water weighs 18 g per mole, so: \[ n_{water} = \frac{1000}{18} = 55.56\ \text{mol} \]
Step 3: Put it in the formula
\[ x_{solute} = \frac{\text{mol solute}}{\text{mol solute} + \text{mol water}} = \frac{2.0}{2.0 + 55.56} = \frac{2.0}{57.56} = 0.0347 \]
Answer: Option (C), the mole fraction is about 0.0347.
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