Question

Calculate the molar concentration of a riboflavin (376.37 g/mol) solution made from (1.1x10^2) mg dissolved up to (6.500x10^2) mL.

Answer 1

To calculate the molar concentration \( C \) of the riboflavin solution, we can use the formula:

\[
C = \frac{n}{V}
\]

where:
- \( n \) is the number of moles of riboflavin,
- \( V \) is the volume of the solution in liters.

**Step 1: Convert mass from mg to grams.**

Given mass of riboflavin = \( 1.1 \times 10^2 \) mg

\[
1.1 \times 10^2 \, \text{mg} = 110 \, \text{mg} = 110 \times 10^{-3} \, \text{g} = 0.110 \, \text{g}
\]

**Step 2: Calculate the number of moles of riboflavin.**

The number of moles \( n \) can be calculated with the formula:

\[
n = \frac{\text{mass}}{\text{molar mass}}
\]

Substituting the values:

\[
n = \frac{0.110 \, \text{g}}{376.37 \, \text{g/mol}} \approx 0.000292 \, \text{mol}
\]

**Step 3: Convert volume from mL to liters.**

Given volume = \( 6.500 \times 10^2 \) mL

\[
6.500 \times 10^2 \, \text{mL} = 650.0 \, \text{mL} = 650.0 \times 10^{-3} \, \text{L} = 0.6500 \, \text{L}
\]

**Step 4: Calculate the molar concentration \( C \).**

Now we can use the number of moles and volume to find the concentration:

\[
C = \frac{n}{V} = \frac{0.000292 \, \text{mol}}{0.6500 \, \text{L}} \approx 0.000449 \, \text{mol/L} \, \text{or} \, 0.449 \, \text{mM}
\]

Thus, the molar concentration of the riboflavin solution is approximately:

\[
\boxed{0.000449 \, \text{mol/L}} \, \text{or} \, \boxed{0.449 \, \text{mM}}
\]