If the density of methanol is 0.793 kg L–1, what is its volume needed for making 2.5 L of its 0.25 M solution?

Q- 12 If the density of methanol is 0.793 kg L–1, what is its volume needed for making 2.5 L of its 0.25 M solution?

Answer
Molar mass of methanol (CH3OH) = (1 × 12) + (4 × 1) + (1 × 16)
                                                  = 32 g mol–1
                                                  = 0.032 kg mol–1   (divide by 1000 to convert in Kg )
Molarity of methanol solution=0.793 Kg L-1/ 0.032 Kg mol -1
                                            = 24.78 mol L–1
 

(Since density is mass per unit volume)
Applying,
                     M1V1                      =                    M2V2
               (Given solution)                 (Solution to be prepared)
(24.78 mol L–1) V1= (2.5 L) (0.25 mol L–1)V1
                     V1 = 0.0252 L   (multiply by 1000 to convert in ml )
                          = 25.22 mL