Question

Reaction of 2.0 L of hydrogen gas with 1.0L of oxygen gas yields 2.0L of water vapor. All gases are at the same temperature and pressure. Show how these data support the idea that oxygen gas is a diatomic molecule. Must we consider hydrogen to be a diatomic molecule to explain these results?

Short answer

Yes, the hydrogen must be considered a diatomic molecule to explain the results.

Step-by-step solution

Gases

All gases are at the same temperature and pressure. So the volumes can be considered equivalent to the moles of gas reaction. 2.0L of hydrogen gas reacts with 1.0L of oxygen gas to give 2.0L of water vapor.

Explanation of formula

The water vapor has the formula: ${\text{H}}_{\text{2}}\text{O}$

One volume of water has one atom of oxygen. We obtain two volumes of water from one volume of oxygen. So, this supports the idea that oxygen gas is a diatomic molecule that splits into individual atoms during the formation of water.

Conclusion

We can also see that one volume of hydrogen gives one volume of water vapor and one volume of water vapor contains two atoms of hydrogen. Hence, hydrogen must be considered a diatomic molecule to explain the results.