Question

$6.02 \times 10^{20}$ molecules of urea are present in 100 mL of its solution. The concentration of solution is :-

• A. 0.1 M
• B. 0.02 M
• C. 0.01 M
• D. 0.001 M

Answer 1

Answer: (C)

Number of moles $=\frac{\text { number of molecules }}{\text { NA }}$ $=\frac{6.02 \times 10^{20}}{6.02 \times 10^{23}}=10^{-3} mol$
Molar conc $=\frac{ n \times 1000}{ V _{\text {solution }}( mL )}=\frac{10^{-3} \times 1000}{100}$
Molar conc. $=0.01 M$