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Question:

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

0.02 M

0.1 M

0.01 M

0.001 M

Solution:

The concentration of the solution is the ratio of the number of moles of urea to (volume in L) of solution.
The number of mols can be obtained from the ratio of the number of molecules to the Avogadro's number.
M = \frac{No of moles of substance}{Volume in Litre} = \frac{no. of particles}{N_A \times Volume in L}
M = \frac{6.02 \times 10^{20}}{6.02 \times 10^{23} \times \frac{100}{1000}} = 0.01 M
Thus, the concentration of the solution is 0.01 M.
Hence, the correct option is B