Question

1. Determine the molality of a solution prepared by dissolving 4.95 g of potassium chloride in 70 g of water. Enter your answer to 2 decimal places

2. Determine the molality of a solution of benzene dissolved in toluene (methylbenzene) for which the mole fraction of benzene is 0.132.   Give your answer to 2 decimal places.

3. How many moles of solute particles are present in 7.89 mL of 0.458 M K₂SO₄? When you have your answer, take the LOG (base 10) of your answer and enter it with 2 decimal places.

Answer 1

molality = number of moles of solute/mass of solvent in kg

molar mass of kcl=74.55g

so 1mole kcl = 74.55 g of kcl

so 4.95 g of kcl= [1mol/74.55 g]*4.95=0.066 mols

mass of water = 70g= 0.07kg

molality= 0.066/0.07 kg =0.94 m