A 50.0 g solution (density = 1.12 g/mL) of potassium fluoride is placed in an evaporating...

A 50.0 g solution (density = 1.12 g/mL) of potassium fluoride is placed in an evaporating dish and the
solvent is evaporated, leaving 8.10 g of solid behind. Calculate the concentration of the solution in units of
a) mass percentage
b) molarity
c) molality

Solutions

Expert Solution

given
mass of solution= 50 g
density of solution = 1.12 g/ml
mass of solute = 8.10g
mass % = mass of solute/Total mass of solution *100
= [8.10 g/50 g]*100 = 16.2 %

Answer 16.2%
**********************
volume of solution = mass/density = 50 g/1.12 g/ml
=44.643 ml = 0.044643 l

molar mass of solute KF = 58.10 g/mol

molarity = mass of solute/molar mass of solute*volume of solution in L
= 8.10 g/58.10 g/mol*0.044643 l
molarity= 3.123 M
**************************
mass of solvent = 50 g- 8.10 g= 41.9 g = 0.0419 kg
molality = mass of solute/molar mass of solute*mass of solvent in Kg
= 8.10 g/58.10 g/mol*0.0419 Kg
molality= 3.327 m
**********************

queen_honey_blossom answered 1 year ago

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