Question

calculate mole fraction of hcl in solution of hcl containing 24.8%of hcl by mass

Answer 1

HCl is 24.8% by mass solution..... ie. 24.8 g HCl in 100 g of water.
So, mass of HCl= 24.8g and mass of water = 100-24.8 = 75.2 g.
 Molar masses are -   HCl = 36.5 g/mol  and water - 18 g/mol
Therefore, no. of  moles of HCl = ( mass of HCl ) /  molar mass of HCl = 24.8/36.5 =  0.68 moles
                  no. of  moles of water = ( mass of water ) / molar mass of water = 75.2 / 18 = 4.18 moles
Hence mole fraction of HCl =  (no. of moles of HCl ) / total no of moles of HCl and water
                                              =  (0.68) / (0.68+4.18) = (0.68) / (4.86)
                                             =  0.139
Hence , mole fraction of HCl in the given solution is 0.139.

Answer 2

0.1399(approx.)

Given:

Percentage by mass of hcl  = 24.8 %

To Calculate:

Mole fraction of the HCl solution

Solving:

Let us assume the solution to be of 100 grams

Mass of solute here it is HCl = 24.8 grams

Calculating the mass of solvent = 100 - 24.8

= 75.2 grams

Calculating the molecular mass of HCl

= 1 g x 1 + 35.5 g x 1

= 36.5 g

Calculating the number of moles of solute

(HCl)

= Given Mass / Molecular Mass

= 24.8 g / 36.5 g

= 0.6795 mol

Calculating the molecular mass of water solvent:

(H2O)

= 1 g x 2 + 16 g x 1

= 2 + 16

= 18 g

Number of moles of water which is the solvent:

= Given Mass / Molecular Mass

= 75.2 g / 18 g

= 4.178 mol

Calculating the total number of moles =

nA + nB

= 4.178 mol + 0.6795 mol

= 4.8575 mol

Mole fraction of HCl which is the solute:

= nB/nA + nB

= 0.6795 / 4.8575

= 0.1399

Therefore, the mole fraction of HCl is 0.1399(approx.)