Question

A solution of glucose in water is labelled as `10 "percent" w//w`, what would be the molality and mole fraction of each component in the solution? If the density of the solution is `1.2 g mL^(-1)`, then what shall be the molarity of the solution?

Answer 1

10% (w/w) solution of glucose means that 10 g of glucose is present in 100 g of solution or 90 g of water.
(a) Calculation of molality
Mass of glucose `=10 g`
Moles of glucose `=10/180=0.0556`
Molar mass of glucose `=180`
Mass of water `=90 g`
Molality `=("Moles of glucose")/("Mass of water") xx 1000`
`=0.0556/90xx1000`
`=0.618 m`
(b) Calculation of molarity
Moles of glucose `=0.0556`
Volume of solution `=("Mass")/("Density")`
`=100/1.20=0.83 ml`
Molarity `=("Moles of glucose")/("Volume of solution") xx1000`
`=0.0556/0.83xx1000`
`=0.0669 M`