Questions: Reference the following balanced equation:
2 H2(g) O2(g) ... 2 H2O(g)
If you have 30.0 g of hydrogen gas burned in excess oxygen gas, how many moles of water can you theoretically make?
60 moles water
7.5 moles water
15 moles water
30 moles water
Transcript text: Reference the following balanced equation:
\[
2 \mathrm{H}_{2}(g) \quad \mathrm{O}_{2(g)} \quad \cdots \quad 2 \mathrm{H}_{2} \mathrm{O}_{(g)}
\]
If you have 30.0 g of hydrogen gas burned in excess oxygen gas, how many moles of water can you theoretically make?
60 moles water
7.5 moles water
15 moles water
30 moles water
Solution
Solution Steps
Step 1: Determine the Molar Mass of Hydrogen Gas
The molar mass of hydrogen gas (\(\mathrm{H}_2\)) is calculated as follows:
\[
\text{Molar mass of } \mathrm{H}_2 = 2 \times 1.008 \, \text{g/mol} = 2.016 \, \text{g/mol}
\]
Step 2: Calculate Moles of Hydrogen Gas
Using the given mass of hydrogen gas, calculate the number of moles:
\[
\text{Moles of } \mathrm{H}_2 = \frac{30.0 \, \text{g}}{2.016 \, \text{g/mol}} = 14.88 \, \text{moles}
\]
Step 3: Use Stoichiometry to Find Moles of Water
According to the balanced chemical equation:
\[
2 \mathrm{H}_2(g) + \mathrm{O}_2(g) \rightarrow 2 \mathrm{H}_2\mathrm{O}(g)
\]
The stoichiometric ratio of \(\mathrm{H}_2\) to \(\mathrm{H}_2\mathrm{O}\) is 1:1. Therefore, the moles of water produced will be equal to the moles of hydrogen gas used:
\[
\text{Moles of } \mathrm{H}_2\mathrm{O} = 14.88 \, \text{moles}
\]
Step 4: Determine the Closest Answer
The closest answer to 14.88 moles of water is 15 moles of water.