Hemoglobin, a protein in red blood cells, carries $\mathrm{O}_{2}$ from the lungs to the body's cells. Iron (as ferrous ion, Fe $^{2+} )$ makes up 0.33 mass $\%$ of hemoglobin. If the molar mass of hemoglobin is $6.8 \times 10^{4} \mathrm{g} / \mathrm{mol},$ how many $\mathrm{Fe}^{2+}$ ions are in one molecule?

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An iron ore sample contains $\mathrm{Fe}_{2} \mathrm{O}_{3}$ together with other substances. Reaction of the ore with CO produces iron metal:

$$

\mathrm{Fe}_{2} \mathrm{O}_{3}(s)+\mathrm{CO}(g) \longrightarrow \mathrm{Fe}(s)+\mathrm{CO}_{2}(g)

$$

(a) Balance this equation.

(b) Calculate the number of grams of CO that can react with 0.350 $\mathrm{kg}$ of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ .

(c) Calculate the number of grams of Fe and the number of grams of $\mathrm{CO}_{2}$ formed when 0.350 $\mathrm{kg}$ of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ reacts.

(d) Show that your calculations in parts (b) and (c) are consistent with the law of conservation of mass.

Iron oxide ores, commonly a mixture of FeO and $\mathrm{Fe}_{2} \mathrm{O}_{3},$ are given the general formula $\mathrm{Fe}_{3} \mathrm{O}_{4}$ . They yield elemental iron when heated to a very high temperature with either carbon monoxide or elemental hydrogen. Balance the following equations for these processes:

$$

\begin{array}{c}{\mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{H}_{2}(g) \longrightarrow \mathrm{Fe}(s)+\mathrm{H}_{2} \mathrm{O}(g)} \\ {\mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{CO}(g) \longrightarrow \mathrm{Fe}(s)+\mathrm{CO}_{2}(g)}\end{array}

$$

When aluminum is mixed with iron (III) oxide, iron

metal and aluminum oxide are produced, along with a

large quantity of heat. What mole ratio would you use

to determine moles of Fe if moles of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ is known?

\begin{equation}

\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{s})+2 \mathrm{Al}(\mathrm{s}) \rightarrow 2 \mathrm{Fe}(\mathrm{s})+\mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{s})+ heat\end{equation}