Question

Calculate the mass of solute required to make an iron(III) chloride solution containing 2.58x102 g of water that has a boiling point of 111 °C Express your answer using three significant figures. I AED * O2 ? Submit Request Answer

Answer 1

Original boiling point of water is 100 oC
Here boiling point is 111 oC

So, elevation in boiling point is 11 oC'

i for FeCl3 is 4 as it dissociates into 1 Fe3+ and 3 Cl-

use:
delta Tb = i*Kb*mb
11.0 = 4.0*0.512 *mb
mb= 5.3711 molal


m(solvent)= 258 g
= 0.258 kg

use:
number of mol,
n = Molality * mass of solvent in Kg
= (5.371 mol/Kg)*(0.258 Kg)
= 1.386 mol

Molar mass of FeCl3,
MM = 1*MM(Fe) + 3*MM(Cl)
= 1*55.85 + 3*35.45
= 162.2 g/mol

use:
mass of FeCl3,
m = number of mol * molar mass
= 1.386 mol * 1.622*10^2 g/mol
= 2.248*10^2 g
Answer: 225 g