Wood and oxygen are two reagents required to keep a campfire burning.
Identify the limiting and excess reagents when:
a) The fire dwindles over time.
b) A carbon dioxide fire extinguisher puts out the flame
In a chemical reaction all the reactants taking part in the reaction are required in a definite ratio. For the reaction to go on all the reactants are required. It is not possible for any reaction to proceed if one of the reactants gets exhausted.
The chemical substance that is completely consumed is referred to as the limiting reagent.
When wood reacts with oxygen, there are many hydrocarbons taking part in the reaction that leads to the formation of carbon dioxide and water.
In the case where the fire dwindles over time, the limiting reagent is the wood. It is the wood getting exhausted that leaves nothing for the oxygen to react with.
On the other hand, when the reaction is put out with a carbon dioxide extinguisher, there is wood left that can take part in the reaction but the oxygen supply required for the reaction is cut off. Here oxygen in the limiting reagent.