Answer
There are $1.97 \times 10^{-3}$ moles in a 300 mg tablet, which means there are $1.19 \times 10^{21}$ $Fe^{2+}$ ions.
Work Step by Step
1. Calculate the molar mass $(FeSO_4)$:
55.85* 1 + 32.07* 1 + 16.00* = 151.92g/mol
2. Calculate the number of moles $(FeSO_4)$
** 300 mg = $300 \times 10^{-3}$ g = 0.300 g
$n(moles) = \frac{mass(g)}{mm(g/mol)}$
$n(moles) = \frac{ 0.300}{ 151.92}$
$n(moles) = 1.97\times 10^{- 3}$
3. Find the amount in moles of $Fe^{2+}$ ions:
** Each $FeSO_4$ has 1 $Fe^{2+}$ ion, so the ratio is 1 to 1.
$1.97 \times 10^{-3} mol (FeSO_4) \times \frac{1 mol (Fe^{2+})}{1 mol (FeSO_4)} = 1.97 \times 10^{-3} mol (Fe^{2+})$
4. Calculate the number of $Fe^{2+}$ ions:
$1.97 \times 10^{-3} mol (Fe^{2+}) \times \frac{6.022 \times 10^{23} ions (Fe^{2+})}{1 mol (Fe^{2+})} = 1.19 \times 10^{21}$ ions $Fe^{2+}$.
