U3-2-4 - Excess Flashcards
Part of the Getting the Most from Reactants topic from Unit 3 of Higher Chemistry, Chemistry in Society
1
Q
Excess reactant
A
A reactant of which we have more than the reaction requires
more than the molar ratio requires
2
Q
Limiting reactant
A
A reactant which is not in excess
not enough of it for all of the other reactant to get used up
3
Q
Which reactant is used in calculations:
excess or limiting?
A
Limiting
4
Q
Which kind of reactant should be used in excess: cheap or expensive?
A
Cheap
So that all of the expensive reactant gets used up
5
Q
Why would we add an excess of a reactant?
A
Any one of:
* so that all of the other reactant gets used up
* reactant in excess is cheaper than the other reactant(s)
* if adding excess acid/alkali, may need acidic/alkaline pH in mixture after reaction.
