Question

How many grams of sucrose will I add to the water (0.100 L) in order to make the 3 molal solution.

Answer 1

Answer:

mass = 102.69 g of sucrose

Explanation:

First, you need to use the correct expression of molality (m) which is the following:

m = moles / kg solvent    (1)

According to the exercise, we need to get the grams, in other words, the mass of the sucrose. To get the mass, we need the moles and molecular weight of sucrose and use the following expression:

moles = mass / MM    (2)

Now, if we replace (2) in (1) we have:

m = mass / MM * kg solvent   (3)

From here, we solve for the mass and then:

mass = m * MM * kg solvent (4)

Now, then density of water is 1 kg/L, so, the volume of the water will be the same as it's mass, and the molality is 3 m. The molecular weight of the sucrose is (according to several sources) 342.3 g/mol. Replacing all the data in (4) we have:

mass = 3 mol/kg * 0.1 kg * 342.3 g/mol

mass = 102.69 g of sucrose

Hope this helps