Question

A solution of Iron (III) chloride is made to be 1.541 m, and 1.457 M in water. Calculate the density of the solution and percent by mass Iron (III) chloride.

Answer 1

Given that the molality of the Iron(III) chloride solution = 1.541 mol /kg water

1.541 mol
`FeCl_(3)`is present per L solution

Calculating mass of
`FeCl_(3)` from 1.541 mol:

`1.541mol FeCl_(3)*(162.20gFeCl_(3))/(1mol FeCl_(3)  )=  249.95 g FeCl_(3)`

Mass of solvent = 1 kg
`*(1000g)/(1kg)=1000g solvent`

Total mass of the solution = 1000 g + 249.95 g = 1249.95 g solution

Density of the solution =
`(1249.95g)/(1000mL)= 1.25g/mL`

Molarity of the solution = 1.457 mol/L solution

Calculating mass of
`FeCl_(3)` from 1.457 mol:

`1.457mol FeCl_(3)*(162.20gFeCl_(3))/(1mol FeCl_(3)  )=  236.3 g FeCl_(3)`

Volume of the solution = 1 L *
`(1000mL)/(1L) =1000mL`

Mass of solution =
`1000mL*(1.25g)/(mL) =1250 g solution`

Mass percentage of
`FeCl_(3)`in the solution =
`(236.3g FeCl_(3) )/(1250 g solution) *100 =18.9 %`

Therefore density of the solution is 1.25 g/mL

Mass percent of the solution is 18.9 %