Find the amount of sucrose required.

Question

What mass of sucrose(C₁₂H₂₂O₁₁)of molar mass 342g is required to make 2.5 kg of 0.25 molal aq. solution ?

Answer 1

1 molal  aqueous solution of glucose contains 1kg water and 1 mole or 342 gm glucose.

So 0.25 molal solution will contain 342×0,25=85,5gm glucose in 1kg water.

Hence 1.0855kg 0.25 molal solution contains 0.0855 gm glucose.

So 2.5kg 0.25 molal aq solution will contain  0.0855×2.5/1.0855 kg glucose = 0.197kg glucose