Question

Define limiting reagent. Use an analogy to explain the concept.



2.5 g of Methane (CH4) is burned in chamber containing 5 g of oxygen. Is the combustion complete?



Give two situations that could cause a percent yield to be less than 100%.




In solution, 2 g of Calcium Chloride is reacted with 5 g of Lead (IV) Nitrate as illustrated in the reaction below. A precipitate is formed and filtered out. The mass of the precipitate is 1.2 g. Determine the percent yield.

2 CaCl2 (aq) + Pb(NO3)4 (aq) 2 Ca(NO3)2 (aq) + PbCl4 (s)

Answer 1

A limiting reagent is a reactant in a chemical process which will dictate how much of the products can be formed.

Consider a combustion reaction (of say methane):

$CH_4(g)+2O_2(g)→CO_2(g)+2H_2O(g)$

There is lots of oxygen in the atmosphere; there is limited methane in your gas bottle. Clearly, here methane is the limiting reagent.

$CH_4(g)+2O_2(g)→CO_2(g)+2H_2O(g)$

methane present in moles = 2.5/16

oxygen present = 5/32

if we the moles of both the reactants are equal

but here stohiometric coefficient of oxygen is 2 which means oxygen will be consumed twice than that methane hence oxygen will be the limiting reagent here and the amount of product formed will depend oxygen