Answer:
it's exothermic reaction, becasue it have negative energy and the temperature increases
a solution containing 1.00 g of an unknown nonelectrolyte liquid and 9.00 g of water has a freezing point of -3.33 *C. Calculate the molar mass of the unknown liquid in g/mol.
The depression in freezing point of water here is 3.33 °C. Then the molality of the solution is 1.79. From number of moles of solute is calculated as 0.0161. Then , the molar mass of the solute is 62.11 g.
What is depression in freezing point ?The addition of a non-volatile salt into a solvent will decrease the freezing point of the solution than the pure solvent. The change in freezing point is proportional to the molality of the solution.
ΔTf = Kf m
Kf is called molal depression constant.
Kf for water = 1.86 °C Kg/mol
given ΔTf = 3.33 (0 - (-3.33))
then m = ΔTf /Kf = 3.33/ 1.86 °C Kg/mol = 1.79
Now, mass of water= 9 g = 0.009 kg
then number of moles = molality × mass of solvent
n = 0.009 kg × 1.79 = 0.0161.
mass of solute taken = 1 g
then, molar mass = 1/0.0161 = 62.11 g.
Therefore, the molar mass of the solute is 62.11 g.
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