Question

How many moles are in 7 milligrams of Carbon-14?

Answer 1

To find the number of moles in a given mass of an element, we can use the formula:

\[
\text{Number of moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}}
\]

1. **Convert the mass from milligrams to grams**:
\[
7 \text{ mg} = 7 \times 10^{-3} \text{ g} = 0.007 \text{ g}
\]

2. **Determine the molar mass of Carbon-14**:
The molar mass of Carbon-14 (C-14) is approximately 14.01 g/mol.

3. **Calculate the number of moles**:
\[
\text{Number of moles} = \frac{0.007 \text{ g}}{14.01 \text{ g/mol}} \approx 0.000499 \text{ moles}
\]

So, the number of moles in 7 milligrams of Carbon-14 is approximately **0.000499 moles** or **4.99 × 10^-4 moles**.