IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry - pl tell me abt limiting reagnts in a reaction...how 2 solve such problm....giv eg

santosh05

pl tell me abt limiting reagnts in a reaction...how 2 solve such problm....giv eg

mukundmadhav

Limiting reagent in a reaction is that reactant that runs out first. So when it's concentration becomes 0, reaction stops. Give an example, and I'll tell how to solve..

santosh05

2h2 + o2-------->2h2o
h is 1oo g n o is 100 g......u hav 2 fin out quantity of watr...pl xpln wat u write

mukundmadhav

Here first you find the moles of each reactant
Now the reactants will react in the ration 2:1
If the number of moles of H2 is more than twice the number of moles of O2, then O2 will run out first, and there will be some remaining H2. The number of moles of H2O formed in this case will be twice the moles of O2 present
If the number of moles of H2 is less than twice the number of moles of O2, then H2 will run out first, and there will be some O2 remaining.
Number of moles of water formed will be equal to the number of moles of H2

In the first case oxygen is the limiting reagent, because it controls the extent to which the raection goes, and in the second case it is Hydrogen
With your numbers, O2 is the limiting reagent because only 5.6 moles of O2 are there while 50 moles of H2 are there
So 11.2 moles of water will be formed

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