Question

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

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

Answer 1

The Correct Option is B

To find the concentration of the solution, we must determine the molarity, which is defined as the number of moles of solute per liter of solution. The steps to find this are as follows:

1. The given number of urea molecules is 6.02 \times 10^{20}.
2. The molar mass of urea (NH₂CONH₂) is approximately 60 g/mol, and 6.022 \times 10^{23} molecules of any substance are equivalent to 1 mole (Avogadro's number).
3. Calculate the number of moles of urea:

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

1. It is given that this amount of urea is dissolved in 100 mL of solution. Convert this volume into liters:

\text{Volume in liters} = \frac{100}{1000} = 0.1 \text{ L}

1. Now, calculate the molarity of the solution using the formula:

\text{Molarity} = \frac{\text{Number of moles of solute}}{\text{Volume of solution in liters}}

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

Therefore, the concentration of the solution is 0.01 M. This matches the second option provided.