Question

A solution of glucose `("molar mass"= 180g mol^(-1))` in water is labelled as 10% (by mass). What would be the molarity and molality of the solution? Given that the density of the solution is `1.2g mL^(-1)`.

Answer 1

Calculaition of glucose=10g
Mass of solution = 100g
Mass of water`= (100-10)`=90g=0.09 kg
Molar mass of glucose=`180gmol^(-1)`
Molality of solution (m)`=("Mass of glucose"//"Molar mass of glucose")/("Mass of solvent in kg")`
`=((10g)//(180"g mol"^(-1)))/((0.09kg))=0.62" mol kg"^(-1)=0.62m`
Calculation of molarity of soluion
Mass of solution =100g
Density of soulution `=1.2 gmL^(-1)`
Volume of solution`=((100g))/((1.2gmL^(-1)))=83mL=0.083L`
Molarity of soution (M) `= ("Mass of glucose"//"Molar mass of glucose")/("Volume of soultion in litres")`
=`=((10g)//(180gmol^(-1)))/((0.083L))=0.67molL^(-1)=0.67 M`