Question

If the mass percentage of urea is 25% (w/w) in
aqueous solution, then the molality of urea in the
solution will be (Molecular weight of urea = 60)
(1) 5.56 m
(2) 2.28 m
(3) 4.25 m
(4) 6.15 m​

Answer 1

Answer:

so 25 % by mass means 25g of urea is present in 100 g of solution

moles of urea = 25/60

=5/12

mass of solute = 25g

mass of solution=100g

mass of solute + solvent = mass of solution

so mass of solvent = 100-25=75g

molalitu = moles of solute × 1000/ mass of solvent(gram)

= 5/12×1000/75

= 5.5m