6.02×1020 molecules of urea are present in 200 mL of its solution. The concentration of urea solution is (N0=6.02×1023mol-1)

Molarity (mol L-1)=Moles of soluteVolume of solution (in L)6.02×1023 molecules of urea = 1 mole ∴6.02×1020 molecules of urea =6.02×10206.02×1023=1×10-3mol200 ml = 0.20 LMolarity =1×10-30.20=0.005M