Question

Determine the mass of 6.29% AlF3 solution that contains 7.92 g of F-.

Answer 1

Molar mass of F = 19 g/mol

mass of F = 7.92 g

we have below equation to be used:

number of mol of F,

n = mass of F/molar mass of F

=(7.92 g)/(19 g/mol)

= 0.4168 mol

This is number of moles of F

one mole of AlF3 contains 3 mole of F

we have below equation to be used:

number of moles of AlF3 = number of moles of AlF3 / 3

= 0.4168 / 3

= 0.1389

Molar mass of AlF3 = 1*MM(Al) + 3*MM(F)

= 1*26.98 + 3*19.0

= 83.98 g/mol

we have below equation to be used:

mass of AlF3,

m = number of mol * molar mass

= 0.1389 mol * 83.98 g/mol

= 11.67 g

This is 6.29 % of mass of solution

use:

mass % of AlF3 = Mass of AlF3*100 /mass of solution

6.29 = 11.67*100/mass of solution

mass of solution = 186 g

Answer: 186 g