Question

A salt solution is found to contain 18.5% Strontium chloride (SrCl₂) by mass. Calculate te mole fractions of SrCl₂ and H₂o. Also calculate the number of Cl atoms in 150 grams of the solution.

Answer 1

molar mass of SrCl₂    = 158.53 g/mole

now, in 100 gm solution 18.5 gm of SrCl₂ is present and (100-18.5) g of H2O is present.

so moles of SrCl₂ = 18.5/158.53 =0.116

moles of H2O = 81.5/18 = 4.52

now,

mole fraction of SrCl2 =0.116/(0.116+4.52)

                                  = 0.025

and mole fraction of H2O = 1-0.025

                                        = 0.975

2)

in 150 grams of solution

mass of SrCl2 = 1.5*18.5 = 27.75 g

moles of Cl = 2* moles of SrCl2

             =   2* 27.75/158.53

            = 0.35

atoms of Cl = 6.023*10^23 * 0.35

              =   2.1 *10^23 atoms