Question #a4a55
1 Answer
(c)
Explanation:
To solve this problem involving freezingpoint depression, we can use the equation
Where

#DeltaT_f# is the change in freezing point temperature (a positive quantity, although the temperature decreases) 
#m# is the molality of the solution, equal to the moles of solute per kilogram of solvent (we'll find this) 
#i# is the van't Hoff factor of the solute, which is given as#1# (it is this value for basically all nonelectrolytes) 
#K_f# is the molal boiling point constant of the solvent, which is given for water as#1.86# #m//""^"o""C"#
We have to find the molality of the sucrose solution.
The number of moles can be found using the given molar mass (
And there are
So the molality is
Now, plugging in our known values, we have
So option (c) is the correct answer. I was taught that the
And since the freezing point lowers, this value is what you would subtract from the normal freezing point of water (
And the new freezing point of the solution is thus