Question

The molality of a solution that is made by dissolving a certain mass of ethanol in 85.4 g of water is 0.950 m. How many moles of ethanol were dissolved? Use mc028-1.jpg. 0.0811 mol 0.0899 mol 11.1 mol 81.1 mol

Answer 1

The moles of  ethanol   is 0.0811 moles

calculation

molarity  = moles of solute/ Kg   of  the solvent

where;

ethanol  is the  solute while water   is the solvent

Molarity = 0.950 M

moles of the solute = ? moles

Kg  of the  solvent = 85.4 /1000 =0.0854 Kg

make moles of  solute the subject of the formula  by  multiplying both side of the formula by Kg of the solvent

moles  of solute =  molarity x Kg  of the solvent

= 0.950  x 0.0854 = 0.0811 moles

Answer 2

Molality = moles of solute /mass of solvent in kg = moles of solute x1000/mass of solvent in gm. Moles of solute = molality x mass of solvent /1000 = 0.95x85.4/1000= 0.0811moles.