Question

A solution was prepared by dissolving 125.0 g of KCl in 275 g of water. Calculate the mole fraction of KCl. (The formula weight of KCl is 74.6 g/mol. The formula weight of water is 18.0 g/mol.)

Answer 1

Answer:

The mole fraction of $KCl$ is $N_{KCl}=0.099$

Explanation:

Generally number of mole is mathematically represented as

                   $n = \frac{mass}{Molar mass }$

 The number of mole of  $KCl$ is

               $n_{KCl} = \frac{mass \ of \ KCl}{Molar\ mass \ of \ KCl }$

                   $n_{KCl} = \frac{125}{74.6}$

                            $=1.676 \ moles$

 The number of mole of  $H_2O$ is

         $n_{H_2O} = \frac{mass \ of \ H_2O}{Molar\ mass \ of \ H_2O }$

         $n_{H_2O} = \frac{275}{18}$

                   $= 15.28 \ moles$

Mole fraction of     $N_{KCl}= \frac{n_{KCl}}{n_{KCl} + n_{H_2O}}$

                                        $= \frac{1.676}{15.28 +1.676}$

                                        $N_{KCl}=0.099$

Answer 2

Answer:

The mole fraction of KCl is 0.13

Explanation:

no of moles of KCl (n KCl)    = W/G.F.Wt

                                                = 135/74.6  

                                                = 1.81moles

no of moles of H2O (nH2O) = W/G.F.Wt

                                              = 225/18   = 12.5 moles

mole fraction of KCl ( XKCl)   = nKCl/nKCl + nH2O

                                                = 1.81/(1.81+12.5)

                                                 = 1.81/14.31  

      The mole fraction of KCl is   = 0.13