6.022*10^20 molecules of urea is present in 100 ml solution.the concentration of urea solution is

if 6.022x10^23 molecules of urea are dissolved in 1 litre then concentration = 1M/litre
so 6.022x10^20are dissolved in 1litre = 1x6.022x10^20/6.022x10^23= 1x10^-3M/ litre
when this amount is dissolved in 100 ml = 1x10^-3x1000/100 = 1x10^-2M
so concentration = 0.01M answer

This quantity given in question can be written as 1*10^-3 moles of urea.
Now in 100 ml solution no. of moles of urea = 1*10^-3
So in 1000 ml of solution no. of moles of urea = 1*10^-2
i.e. in 1 L solution no. of moles of urea = 1*10^-2.

Hence concentration=0.01 moles /liter = 0.01 M

the concentration is 0.01 mol/litre.