6.02x 10²⁰ molecules of urea are present in 100 mL of its solution. The concentration of solution is

Given number of molecules of urea $=6.02\times {10}^{20}$
$\therefore$Number of moles $=\frac{6.02\times {10}^{20}}{6.02\times {10}^{23}}=1\times {10}^{-3}\mathrm{mol}$
Volume of the solution $=100\mathrm{mL}=\frac{100}{1000}\mathrm{L}=0.1\mathrm{L}$
Concentration of urea solution (in mol L^-1)
                                 $\begin{array}{r}=\frac{1\times {10}^{-3}}{0.1}=1\times {10}^{-2}{\mathrm{molL}}^{-1}\\ =0.01\mathrm{mol}/\mathrm{L}\text{ or }\mathrm{M}\end{array}$