Concepts of Limiting & Excess Reactants are so commonly tested in school exams as well as ‘O’ Levels Chemistry examinations. However, many students seemed to have very weak foundation of the essential concepts surrounding it.
Before we even visit any question, it is important to understand the definition of both reactants.
Limiting Reactant:
– The reactant that is completely used up in a chemical reaction
– It determines or limits the amount of products formed in a reaction
Excess Reactant:
– The reactant that are not used up in a chemical reaction
– There is always an excess at the end of the reaction, stays unreacted
Example:
Reaction of hydrogen gas with chlorine according to the equation below:
H2 (g) + Cl2 (g) → 2HCl (g)
We can see that 1 mole of H2 reacts with 1 mole of Cl2 to form 2 moles of HCl
Scenario A: When 1 mole of H2 added to 1 mole of Cl2
Results: 2 moles of HCl are [Read more…] about O Level Chemistry: Mole Calculations – Limiting & Excess Reactants