1. 12.3
Limiting Reactant
If a carpenter had two tabletops and seven table legs, he could only build one table. The number of table legs is the
limiting factor.
In chemistry, the amount
of product made in a
chemical reaction is
limited by the amount of
one of the reactants.
Print 1-2,4-7

2. 12.3
In a chemical reaction, an insufficient amount of one of the reactants will limit the amount of product that forms.
limiting reactant:
the reactant that determines the amount of product that can be formed.

3. Limiting and Excess Reagents
12.3
Limiting and Excess Reagents
The “recipe” calls for 3 molecules of H2 for every 1 molecule of N2 . In this particular experiment, H2 is the limiting reagent and N2 is in excess.

4. Limiting and Excess Reagents
12.3
Limiting and Excess Reagents
The “recipe” calls for 3 molecules of H2 for every 1 molecule of N2 . In this particular experiment, H2 is the limiting reagent and N2 is in excess.
excess
limiting

5. To determine which is the LR:
12.3
To determine which is the LR:
convert both reactants to mol of same product
the one that makes less product is the LR

6. Determining Limiting Reactant
12.2
Determining Limiting Reactant
Which is the limiting reactant when
48.0 g Mg is reacted with 108 g HCl?
Mg HCl → MgCl2 + H2
1 mol Mg
24.31 g Mg
1 mol H2
1 mol Mg
48.0 g Mg x x =
1.97 mol H2
1 mol HCl
36.46 g HCl
1 mol H2
2 mol HCl
108 g HCl x x =
1.48 mol H2
HCl is limiting 6

7. Determining Limiting Reactant
12.2
Determining Limiting Reactant
How many grams CO2 can be formed from
2.70 mol C2H4 is reacted with 6.30 mol O2?
C2H O2 → 2 CO H2O
2 mol CO2
1 mol C2H4
2.70 mol C2H4 x =
5.40 mol CO2
2 mol CO2
3 mol O2
6.30 mol O2 x =
4.20 mol CO2
44.01 g CO2
1 mol CO2
4.20 mol CO2 x =
185 g CO2 7

8. HNO3: 63.02 g/mol NO2: 46.01 g/mol H2O: 18.02 g/mol Quick Quiz!
1. In the reaction,
3 NO2 + H2O  2 HNO3 + NO
how many grams of HNO3 can form when 1.00 g of NO2 and 2.25 g of H2O are reacted?
0.913 g
0.667 g
15.7 g
1.37 g
HNO3: g/mol
NO2: g/mol
H2O: g/mol

9. Quick Quiz.
2. How many grams of H2O can be formed from g O2 and 2.97 mol H2?
2 H2 + O2  2 H2O
30.0 g
27.0 g
54.0 g
13.5 g