How to calculate volume of gas produced in a chemical reaction?
Answers
TL;DR There is twice the amount of SO3 produced compared to oxygen, thus the volume will be twice as much as oxygen. Therefore 8.4 litres of SO3 will be produced.
Since SO2 is in excess, the amount of SO3 produced will be twice as the amount of moles of oxygen. So if there is originally x moles of oxygen gas, 2x moles of SO2 is produced. It is important to note that temperature and pressure remain constant throughout the reaction.
Note one of gas laws state, the same number of moles of any gaseous substance will have the same volume at constant temperature and pressure. So x moles of SO3 will hold the same volume as x moles of oxygen gas, so 4.2 litres.
Now there is also another gas law which states that the volume of a gas is directly proportional to the number of moles of the substance. So 2x moles of SO3 will have twice the volume of x moles of SO3. Therefore the volume of 2x moles of SO3 will be 8.4 moles.
Therefore the answer is 8.4 litres