Calculate the molality of a solution prepared by dissolving 31.6 g of Fe2O3 in 750. g of water
Someone must have made this up out of thin air!
It won't dissolve in water; however, if it would the molarity would be done this way. AND we must assume 75 g of water = 75 mL AND we must assume no volume change upon adding the Fe2O3.
mols = grams/molar mass
M = moles/L soln.
0.007
To calculate the molality of a solution, you need to know the mass of the solute and the mass of the solvent. In this case, the solute is 31.6 g of Fe2O3, and the solvent is 750. g of water.
Molality (m) is defined as the number of moles of solute per kilogram of solvent. Therefore, we need to convert the mass of the solute and solvent into moles.
First, let's convert the mass of Fe2O3 into moles. To do this, we need to know the molar mass of Fe2O3, which can be found in the periodic table.
The molar mass of Fe2O3 is calculated as follows:
(2 × atomic mass of Fe) + (3 × atomic mass of O)
= (2 × 55.845 g/mol) + (3 × 16.00 g/mol)
= 111.69 g/mol + 48.00 g/mol
= 159.69 g/mol
Now, we can calculate the number of moles of Fe2O3:
moles of Fe2O3 = mass of Fe2O3 / molar mass of Fe2O3
= 31.6 g / 159.69 g/mol
= 0.1977 mol
Next, we need to convert the mass of water into kilograms:
mass of water = 750. g = 0.750 kg
Finally, we can calculate the molality (m):
molality (m) = moles of solute / kilograms of solvent
= 0.1977 mol / 0.750 kg
= 0.2636 mol/kg
Therefore, the molality of the solution prepared by dissolving 31.6 g of Fe2O3 in 750. g of water is 0.2636 mol/kg.