Which solution has the lowest freezing point?
(1) 10. g of ki dissolved in 100. g of water
(2) 20. g of ki dissolved in 200. g of water
(3) 30. g of ki dissolved in 100. g of water
(4) 40. g of ki dissolved in 200. g of water

Correct Option 3 i.e. 30 g of KI dissolved in 100 g of water.

Reason:
Depression in freezing point is a colligative property and it is directly proportional to molality of solution.

Molality of solution is mathematically expressed as,
Molality = 

In case of option 1 and 2, molality of solution is 0.602 m. For option 3, molality of solution is 1.807 m, while in case of option 4, molality of solution is 1.205 m.

Thus, second solution (option 2) has highest concentration (in terms of molality). Hence, it will have lowest freezing point

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