How many moles of oxygen gas [tex]\(\left( O_2 \right)\)[/tex] are needed to completely react with 54.0 g of aluminum?

[tex]\[
4 \text{Al} + 3 \text{O}_2 \rightarrow 2 \text{Al}_2 \text{O}_3
\][/tex]

Let's set up the conversions first.

What goes in the green box?

[tex]\[
\begin{tabular}{l|c|c}
54.0 g \text{Al} & {[?]} & {[]} \\
\hline
& {[?]} & {[]} \\
\end{tabular}
\][/tex]

Options:
1. 4 mol Al
2. 3 mol O[tex]\(_2\)[/tex]
3. 26.98 g Al



Answer :

To find the number of moles of oxygen gas ([tex]\(O_2\)[/tex]) needed to react with 54.0 grams of aluminum ([tex]\(Al\)[/tex]), we can follow these steps:

1. Calculate the number of moles of aluminum:
First, we'll convert the mass of aluminum to moles using the molar mass of aluminum. The molar mass of [tex]\(\text{Al}\)[/tex] is 26.98 g/mol.

[tex]\[ \text{Moles of Aluminum} = \frac{\text{Mass of Aluminum}}{\text{Molar Mass of Aluminum}} = \frac{54.0 \text{ g}}{26.98 \text{ g/mol}} \][/tex]

It comes out to approximately 2.0015 moles of aluminum.

2. Determine the mole ratio from the balanced chemical equation:
The balanced chemical equation is:
[tex]\[ 4 \text{Al} + 3 \text{O}_2 \rightarrow 2 \text{Al}_2\text{O}_3 \][/tex]
From this equation, we see that 4 moles of [tex]\(\text{Al}\)[/tex] react with 3 moles of [tex]\(\text{O}_2\)[/tex].

Therefore, the mole ratio of [tex]\(\text{Al}\)[/tex] to [tex]\(\text{O}_2\)[/tex] is:
[tex]\[ \frac{3 \text{ moles} \, \text{O}_2}{4 \text{ moles} \, \text{Al}} = 0.75 \][/tex]

3. Calculate the moles of oxygen gas needed:
Using the number of moles of aluminum and the mole ratio, we can find the moles of [tex]\(\text{O}_2\)[/tex] needed.

[tex]\[ \text{Moles of Oxygen Gas} = \text{Moles of Aluminum} \times \text{Mole Ratio} = 2.0015 \text{ moles Al} \times 0.75 \][/tex]

This calculation gives us approximately 1.5011 moles of oxygen gas.

Therefore, 1.5011 moles of oxygen gas ([tex]\(O_2\)[/tex]) are needed to completely react with 54.0 grams of aluminum ([tex]\(\text{Al}\)[/tex]).

To fill in the conversion factors in the given table:

[tex]\[ \begin{tabular}{l|c|c} 54.0 g Al & \boxed{\text{1 mole Al}} & \boxed{\text{26.98 g Al}} \\ \hline & \boxed{\text{3 moles O}_2} & 4 moles Al \\ \end{tabular} \][/tex]

Here, the green box should contain "26.98 g Al", as it is the molar mass of aluminum.