Osmotic P and molar mass problem?
Im doing online homework but I keep getting this problem wrong. Somebody help me out.
A 1.120 g sample of a nonelectrolyte is dissolved in sufficient water to make a 0.300 L solution. The resulting solution has an osmotic pressure of 21.4 torr at 280 K. Find the molar mass of the substance in g/mol.
Procedure:
(1) Solve π = MRT for M and find M. Careful, what units must be used for π?
(2) Recall M = mol solute/L solution.
(3) Multiply M by L solution to get moles solute.
(4) Recall the definition of molar mass is g/mol. Simply divide the mass of the solute by the number of moles this mass corresponds to.
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Verified answer
p = 21.4 / 760= 0.0282 atm
M = osmotic pressure / RT = 0.0282 / 0.0821 x 280 = 0.00123
moles = 0.00123 x 0.300 L = 0.000368
Molar mass = 1.120 g/ 0.000368 mol= 3043 g/mol