What is the mole fraction of lif in an aqueous solution that contains 39.4% lif (weight/weight %)?

The solution contains 39.4% of LiF. Assume that the solution is 100ml. The molar mass of LiF is 25.939, the amount of LiF in mole would be: 100ml * 1g/ml * 39.4%/ 25.939g/mol= 1.52 mol LiF
Then the mass of the water would be: 100gram- 39.4g= 60.6g
If the molar mass of water is 18.015 the mole of the water would be: 60.6g/ 18.015g/mol= 3.36 mol
.
The mole fraction would be:1.52 mol/ 1.52+3.36= 0.339

They can measure  the amount of energy gained or lost

Thermohaline circulation and gyres