Questions: You measured that 0.219 grams of FeSO4 · 7 H2O were added to the Erlenmeyer flask. Calculate how many moles of FeSO4 · 7 H2O were added to the Erlenmeyer flask. Hint: You calculated the molar mass to be 278 g / mol. Use this to convert 0.219 g to moles.

Calculate the number of moles of \(\mathrm{FeSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}\) added to the Erlenmeyer flask.

Determine the given mass of \(\mathrm{FeSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}\).

The given mass is \(0.219 \, \text{g}\).

Use the molar mass to convert grams to moles.

The molar mass of \(\mathrm{FeSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}\) is \(278 \, \text{g/mol}\). Use the formula:
\[ \text{moles} = \frac{\text{mass}}{\text{molar mass}} = \frac{0.219 \, \text{g}}{278 \, \text{g/mol}} \]
Calculating this gives:
\[ \text{moles} = 0.000788 \, \text{mol} \]

\(\boxed{0.000788 \, \text{mol}}\)

\(\boxed{0.000788 \, \text{mol}}\) of \(\mathrm{FeSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}\) were added to the Erlenmeyer flask.