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

The Correct Option is C

To find the concentration of the urea solution, we need to determine the molarity. Molarity (M) is defined as the number of moles of solute per liter of solution. The steps are as follows:

1. Determine the number of moles of urea from the given number of molecules:

The formula to convert molecules to moles is:

\text{Number of moles} = \frac{\text{Number of molecules}}{\text{Avogadro's number}}

Where Avogadro's number is 6.022 \times 10^{23} molecules/mole.

2. Calculate the moles of urea:

\text{Number of moles} = \frac{6.02 \times 10^{20}}{6.022 \times 10^{23}} \approx 1 \times 10^{-3} \text{ moles}

3. Calculate the molarity of the solution:

The given solution has a volume of 100 mL, which is equivalent to 0.1 \text{ L}.

Molarity is given by:

M = \frac{\text{Number of moles}}{\text{Volume in liters}}

Substituting the known values:

M = \frac{1 \times 10^{-3}}{0.1} = 0.01 \text{ M}

4. Conclude:

Therefore, the concentration of the urea solution is 0.01 \text{ M}, which matches the correct option.