Calculate the mass of urea (NH_(2)CONH_(2)) required to prepare 2.5 kg of 0.25 molal aqueous solution.

Calculate the mass of urea (NH_(2)CONH_(2)) required to prepare 2.5 kg

1.	Calculate the mass of urea (NH_(2)CONH_(2)) required to prepare 2.5 kg of 0.25 molal aqueous solution.
Answer» Solution :Molality of solution `= ("Mass of UREA/MOLAR mass of urea")/("Mass of water in kg.")` Molality of solution `=0.25 m=("0.25 mol kg"^(-1))` Molar mass of urea `(NH_(2)CONH_(2))=2xx14+1xx12+1xx16+4xx1=60 "g mol"^(-1)` Mass of solvent (water) = 2.5 kg `("0.25 mol kg"^(-1))=("Mass of urea")/(("60 g mol"^(-1))XX("2.5 kg"))` Mass of urea `=("0.25 mol kg^(-1))xx("60 g mol"^(-1))xx(2.5 kg)` `= 38.5 g`.