Question

Calculate the molarity and molality of a solution of 50 grams of ethanol, C2H5OH (density = 0.789 g/mL) which is dissolved in 200 mL of water (density = 1.00 g/mL).​​

Please show all work with the correct answer. Thank you!!!

Answer 1

In this question, solvent is water and solute is ethanol

molecular weight of ethanol = 46.06 g

moles of ethanol = given weight/ mol. weight

                         = 50/ 46.06 =1.0855 moles

volume of ethanol = mass/ density

                          = 50/0.789 = 63.371 mL

Total volume of solution = 63.371 + 200 = 263.371 mL = 0.263371L

Molarity = moles/Volume in litre

             = 1.0855/0.263317 = 4.1215 M

now , mass of water = density*volume

                              = 1*200 = 200gm = 0.2

molality = moles of solute/weight of solvent in Kg

             = 1.0855/0.2

              = 5.4275m