Editing Limiting reagent (section)

{{Short description|Chemical reactant totally consumed when the reaction is finished}}
{{refimprove|date=June 2015}}
[[File:Reagente limitante.svg|thumb|right|300px|Equal masses of iron (Fe) and sulfur (S) react to form iron sulfide (FeS), but because of its higher atomic weight, iron is the limiting reagent and once all the iron is consumed some sulfur remains unreacted]]
The '''limiting reagent''' (or '''limiting reactant''' or '''limiting agent''') in a [[chemical reaction]] is a [[reactant]] that is totally consumed when the chemical reaction is completed.<ref> {{cite book |last1=Olmsted |first1=John |last2=Williams |first2= Gregory M. |date=1997 |title=Chemistry: The Molecular Science|url=https://books.google.com/books?id=1vnk6J8knKkC |publisher=Jones & Bartlett Learning |page=163 |isbn=0815184506}}</ref><ref>{{cite book | author = Zumdahl, Steven S. | title = Chemical Principles | edition = 4th | location = New York | publisher = Houghton Mifflin Company | date = 2006 | isbn = 0-618-37206-7}}</ref> The [[amount of substance|amount]] of product formed is limited by this reagent, since the reaction cannot continue without it. If one or more other reagents are present in excess of the quantities required to react with the limiting reagent, they are described as ''excess reagents'' or ''excess reactants'' (sometimes abbreviated as "xs"), or to be in ''abundance''.<ref>{{cite book|title=Chemistry: Principles and Reactions|first1=William L.|last1= Masterton|first2= Cecile N. |last2=Hurley |edition =6|publisher =Cengage Learning|year=2008 |isbn =978-0-495-12671-3}}</ref>

The limiting reagent must be identified in order to calculate the [[yield (chemistry)|percentage yield]] of a reaction since the theoretical yield is defined as the amount of product obtained when the limiting reagent reacts completely. Given the balanced [[chemical equation]], which describes the reaction, there are several equivalent ways to identify the limiting reagent and evaluate the excess quantities of other reagents.