Question

Given 2H2 + O2 --> 2H2O. How many moles of oxygen are required to react completely with 1.2 grams of hydrogen to form water?
Responses

0.3 mol
0.3 mol

4 mol
4 mol

0.5 mol
0.5 mol

1.2 mol
1.2 mol

Answer 1

To determine how many moles of oxygen are required to react completely with 1.2 grams of hydrogen to form water, we can follow these steps:

1. **Calculate the number of moles of hydrogen (H2)**:
The molar mass of H2 (hydrogen gas) is approximately 2.02 g/mol (since hydrogen has a molar mass of about 1.01 g/mol and there are 2 atoms in H2).

\[
\text{Moles of } H2 = \frac{\text{mass of } H2}{\text{molar mass of } H2} = \frac{1.2 \text{ g}}{2.02 \text{ g/mol}} \approx 0.594 \text{ mol}
\]

2. **Use the stoichiometry of the reaction**:
The balanced equation is:
\[
2H2 + O2 \rightarrow 2H2O
\]
From the equation, we see that 2 moles of H2 react with 1 mole of O2. Therefore, the mole ratio of H2 to O2 is 2:1.

To find the required moles of O2, we can use the ratio:
\[
\text{Moles of } O2 = \frac{0.594 \text{ moles } H2}{2} = 0.297 \text{ mol}
\]

This can be approximated as 0.3 mol when rounded.

3. **Conclusion**:
Therefore, the answer is **0.3 mol** of O2 is required to react completely with 1.2 grams of H2 to form water.