Question

a solution of 12.5 g of an unknown solute in 170g water gave a boiling point elevation of 0.63 K. Calculate the molar mass of the solute ( Given that Kb =0.53 K Kg mol-1)​

Answer 1

A solution of 12.5 g of an unknown solute in 170 g water gave a boiling point elevation of 0.63 K. So the molar mass of solute is 61.85 g mol^-1.

1) Given information in question-

    mass of solution $W_{B}$ =12.5g

    mass of water   $W_{A}$ = 170g = 0.170 kg

    Boiling temperature Δ$T_{b}$ =0.63 K

                $K_{b} =0.53 Kg mol^-1$

     molar mass of solute = ?

2) findind molar mass of solute

             molar mass of solute Δ$M_{B} = \frac{K_{b}*W_{B}  }{DT_{b} *W_{A} }$

                        $M_{B} = \frac{0.53*12.5}{0.63*0.170} \\M_{B} = 61.85 g mol^-1$