Question

a. suppose you have been asked to make 2 liters of sucrose syrup at a concentration of 15% w/v how many grams of sucrose would you add?
b. assuming that 1 gram of water is 1 mL of water, what is the molality (m) of the sucrose in the solution question a?

Answer 1

a)

concentration = 15 % (w / v)

volume of syrup = 2 L

15 g of sucrose in --------- 100 mL of solution

?? g                     --------> 2 L solution

mass of sucrose = 2 x 1000 x 15 / 100

mass of sucrose add = 300 g

b)

moles of sucrose = 300 / 342.3 = 0.876

mass of water = 2000 g - 300 g = 1700 g

                       = 1.7 kg

molality = moles / mass of solvent in kg

             = 0.876 / 1.7

molality = 0.52 m