Solution: We know that
The molarity of a solution is defined as M = number of moles of solute/ Volume of solution (in litres) = (mass of solute/ molar mass of solute)X (1/ Volume of solution (in litres)
Let x g of methanol (molar mass = 32g) be required to prepare a 0.25 Molar solution of methanol.
Therefore we have 0.25 = (x/32) X (1/2.5)
x = 20g = 0.02 Kg
Now density = Mass/ Volume
We are given that the density of methanol is 0.793 KgL-1.
Therefore, Volume = Mass/ Density = 0.02/0.793 = 0.025 Litres
Therefore 0.025 Litres of methanol would be required.