Question

Assume the sucrose solution was at a 50% (w/v) solution and 5 liters were made. (assume 1 mL = 1g)

A) What is the initial molatiy of this solution?

B) The sucrose is hydrolyzed. What is the molaity of the new solution in the hydrolyzed sucrose solution?

Answer 1

Ans :

A)

The volume of solution 5 liters

Now since the solution is 50% (w/v) , the amount of sucrose in it will be 2.5 kg = 2500 g

Number of moles = given mass / molar mass

= 2500 / 342.2965

= 7.3 mol

Mass of solvent = mass of solution - mass of sucrose

= 5 - 2.5 = 2.5 kg

Molality = mol / mass of solvent in kg

= 7.3 / 2.5

= 2.92 m

B) The sucrose hydrolyses into glucose and fructose

So now there are double number of moles of solute.

Total number of moles = 2 x 7.3

= 14.6 mol

Molality = 14.6 / 2.5

= 5.84 m