An aqueous solution of 17.5g of an unknown covalent compound in 100.0g of water has a freezing point of -1.8C. Calculate the molar mass of the compound. Kf for water is 1.86C/m
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An aqueous solution of 17.5g of an unknown covalent compound in 100.0g of water has a freezing point of -1.8C. Calculate the molar mass of the compound. Kf for water is 1.86C/m
Solution:
Regular freezing point of water is 0C. The freezing point of a solution is -1.8C. ΔTf = -1.8C-0C= -1.8C i=1 because the compound is covalent. Let's now plug and solve for m (molality).
-1.8C = -1*1.86 C/m (m) m = 0.9677419
m= moles of solute/ kg solvent The solvent is water. 100.0g= 0.1000kg
0.9677419 = moles of solute/ 0.1000kg
moles of solute = 0.09677419moles
Molar mass = 17.5g/0.09677419moles= 180.8333g/mol = 1.8*10^2g/mol
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