How do you determine molality of a substance, when given density, molarity, and molar mass?
I understand how to solve the problem if I am given a volume for the substance, but I dont understand how to calculate it with the given information.
Density= 1.17g/ml
M=0.464
Molar mass=144.6g/mol
m=?
The I learned was, D*V(ml)=M will give me to volume in grams, then I can move on to solving for # of mols.
Any tips or advice is greatly appreciated.
Answers
Suzanne
Thank you very much
Some Body
Density is mass per volume (g/mL). Molarity is moles of solute per liter of solution. Molar mass is moles per gram. Molality is moles of solute per kilogram of solvent. The simple way to solve this is to assume a volume of 1 L. The mass of 1 L of solution is: 1.17 g/mL * 1000 mL/L * 1 L = 1170 g The mass of solute is: 0.464 mol/L * 1 L * 144.6 g/mol = 67.1 g So the mass of solvent is: 1170 g - 67.1 g = 1102.9 g = 1.10 kg The moles of solute are: 0.464 mol/L * 1 L = 0.464 mol So the molality is: 0.464 mol / 1.10 kg = 0.421 mol/kg
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