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garik1379 [7]
3 years ago
15

Which solution has the lowest freezing point?

Chemistry
2 answers:
REY [17]3 years ago
6 0

Answer: (3) 30 g of KI dissolved in 100 g of water

Explanation: Formula used for lowering in freezing point is,

\Delta T_f=k_f\times m

or,

\Delta T_f=k_f\times \frac{w_{solute}}{M_{solute}\times M_{solvent}\text{ (in kg)}}

where,

T_f = change in freezing point

k_f = freezing point constant

m = molality

1) 10 g of KI dissolved in 100 g of water:

\Delta T_f=1.86\times \frac{10}{166\times 0.1}=1.16^0C

2) 20 g of KI dissolved in 200 g of water

\Delta T_f=1.86\times \frac{20}{166\times 0.2}=1.12^0C

3) 30 g of KI dissolved in 100 g of water

\Delta T_f=1.86\times \frac{30}{166\times 0.1}=3.36^0C

As the depression is maximum, the solution will have lowest freezing point.

4)  40 g of KI dissolved in 200 g of water

\Delta T_f=1.86\times \frac{40}{166\times 0.2}=2.24^0C

Leokris [45]3 years ago
3 0
<span>Correct Answer: 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 = </span>\frac{\text{Number of moles}}{\text{Weight of solvent (Kg)}}<span>

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.

<u><em>Thus, second solution (option 2) has highest concentration (in terms of molality). Hence, it will have lowest freezing point</em></u></span>
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