Question

Calculate the number of moles of methanol in 5 litres of its 2 m solution if the density of solution is 0.981 kg (Molar mass of methanol=32.0g `mol^(-1)`.

Answer 1

2 m solution of methanol means that 2 moples of methanol are dissoved in 1 kg (1000g) of water. Mass of methnol `(CH_(3)OH)` in 2 moles`=(2mol)xx(32.0gmol^(-1))=64.0kg`
Dencity of solution =`0.981kgL^(-1)`
Volume of solution `= (Mass)/(Density)=((1.064kg))/(0.981kgL^(-1))=1.085L`
Now, 1.085 L of solution contain methanol =2mol
5.0L of soultion contain mehanol`=((2mol))/((1.085L))xx(5.0L)=9.22` mol.