The molar mass of a compound expresses the ratio of mass to moles: mass in grams

Question

The molar mass of a compound expresses the ratio of mass to moles: mass in grams molar mass = number of moles This quantity can be determined experimentally by mass of the sample and determining the corresponding number of moles based on some property of the sample. Freezing-pointd osmotic pressure measurements are frequently used to calculate the number of moles in solution for this type of determination. Freezing-point depression is equal to where T is the change in temperature, is the molal freezing-point- depression constant, and m is the molality in moles of solute per mass of solvent. Osmotic pressure is equal to II MRT where 11 is the osmotic pressure, R 0.08206 L-atm/(K-mol). T is temperature, and M is molarity in moles per liter of solution

Explanation / Answer

Osmotic pressure = concentration * R * T
0.138 = Concentration * 0.08206 * ( 28 + 273.15 )

Concentration = 0.00558 mol/L

Moles of subunit = 0.00558 * 2.00 / 1000 = 0.0000112 mol

Mass / molar mass = 0.0000112

0.140 / 0.0000112 = molar mass

Therefore,

Molar mass of protein = 12535 g/mol

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