Question

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

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

Answer 1

The correct option is C $0.01M$

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