Answer:
a. 2.959x10⁻²m
b. 5.327x10⁻⁴
c. 0.272%
d. 2718 PPM
Explanation:
A solution of 2.950x10⁻²M contains 2.950x10⁻² moles of Glycerol per Liter of solution. As the volume of the solution made was 1.000L, moles of glycerol are 2.950x10⁻².
a. molality: Molality is defined as the ratio between moles of solute (2.950x10⁻²) in kg of solvent. As there are 998.7mL of solvent and density is 0.9982g/mL, kg are:
998.7mL ₓ (0.9982g/mL) ₓ (1kg / 1000g) = 0.9969kg of solvent.
Molality: 2.950x10⁻² moles / 0.9969kg of solvent = 2.959x10⁻²m
b. Mole fraction is the ratio between moles of solute and total moles. Moles of water are:
998.7mL ₓ (0.9982g/mL) ₓ (1mol / 18.01g) = 55.35 moles of water.
Mole fraction glycerol:
2.950x10⁻² moles / (2.950x10⁻²moles + 55.35) = 5.327x10⁻⁴
c. Percent by mass Is the ratio by mass of solute and solution multiplied 100 times.
Mass of glycerol (Molar mass: 92.09g/mol):
2.950x10⁻² moles × (92.09g / mol) = <em>2.717g of glycerol</em>
Mass of water:
998.7mL ₓ (0.9982g/mL) = <em>996.9g of water.</em>
Percent by mass:
2.717g of glycerol / (996.9g of water + 2.717g) × 100 = 0.272%
d. Parts per million are defined as the ratio between mg of solute and kg of solution.
mg of 2.717g of glycerol are <em>2717mg</em>
kg of solution are (996.9g + 2.717g) / 1000 = <em>0.9996kg</em>
Parts per million:
2717mg / 0.9996kg = 2718 PPM
