The molality of a urea solution in which 0.0100 g of urea, NH22CO  is  added  to  0.3000  dm3 of water at STP is

Molality=moles  of  the  solutemass of the  solvent  in  kgMoles of ureanurea  =  0.0100g60 g mol−1Mass  of  1000  mL  of  solution  =  volume  ×  density                    =300  mL ×  1gmL                 ∵    1  dm3  =  1000  mL                      =300  gMass of  solvent=300  g−0.0100  g=299.9  g=0.2999  kgMolality=0.010060  ×  0.2999  =  5.55 ×  10−4  mol  kg−1