What is a limiting reactant?

Hint :We know that the Limiting reagents are defined as the substances which are entirely consumed in the completion of a chemical reaction. They are also referred to as limiting reactants or limiting agents. According to the stoichiometry of chemical reactions, a fixed amount of reactants is necessary for the reaction to complete.

Complete Step By Step Answer:
When a reaction occurs there is the formation of products and there are many factors that can be used to decide the amount of the formation of the product. So, one of the factors is limiting reagent in the reaction. There are two parts in the reaction or specifically saying on the reactant side. These are excess reagents and limiting reagents. The one which is more in quantity even after the products are formed in excess reagent and the one which is completely used in the reaction, whose quantity decides the quantity of product formed in the reaction, is called the limiting reagent.
There are two ways for how to calculate limiting reagent. One method is to find and compare the mole ratio of the reactants that are used in the reaction. Another method is to calculate the grams of products produced from the quantities of reactants in which the reactant which produces the smallest amount of product is the limiting reagent.
Consider a combustion reaction (methane): $ C{{H}_{4\left( g \right)}}+2{{O}_{2\left( g \right)}}\to C{{O}_{2\left( g \right)}}+2{{H}_{2}}{{O}_{\left( g \right)}} $
There is lots of oxygen in the atmosphere; there is limited methane in your gas bottle. Clearly, here methane is the limiting reagent. Many problems require us to identify the limiting reagent. If we have a stoichiometric equation, most of the time the limiting reagent is easily designated.

Note :
Remember that for finding the limiting and excess reagent in the reaction, the reaction must be balanced. If the reaction is not balanced, the number of moles of the reactants will be wrong which is used for finding the limiting reagent.