The density of a 3.37m mgcl2 (fw = 95.21) is 1.25 g/ml. calulate the molality, mass/mass percent, and mass/volume percent. so far this is what i have, but i cannot get the correct values for the mass of the solution to even begin to figure out the volume.

Answer : The molality, mass/mass percent, and mass/volume percent are, 0.0381 mole/Kg, 25.67 % and 32.086 % respectively.

Solution : Given,

Density of solution = 1.25 g/ml

Molar mass of (solute) = 95.21 g/mole

3.37 M magnesium chloride means that 3.37 gram of magnesium chloride is present in 1 liter of solution.

The volume of solution = 1 L = 1000 ml

Mass of (solute) = 3.37 g

First we have to calculate the mass of solute.

Now we have to calculate the mass of solution.

Mass of solvent = Mass of solution - Mass of solute = 1250 - 320.86 = 929.14 g

Now we have to calculate the molality of the solution.

The molality of the solution is, 0.0381 mole/Kg.

Now we have to calculate the mass/mass percent.

The mass/mass percent is, 25.67 %

Now we have to calculate the mass/volume percent.

The mass/volume percent is, 32.086 %

Therefore, the molality, mass/mass percent, and mass/volume percent are, 0.0381 mole/Kg, 25.67 % and 32.086 % respectively.

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

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