Limiting and Excess Reactants
Unit 8 Pages 8-9
Learning Target:
I can perform stoichiometric calculations involving limiting reagents.
Criteria for Success:
I can define limiting reactant.
I can define excess reactant.
I can use stoichiometry calculations to determine the identity of a limiting and/or excess reactant in a chemical reaction.
Limiting and Excess Reactants
A. The _______________________ ___________________ is the reactant that limits the amounts of the other reactants
that can combine and the amount of product that can form in a chemical reaction.
B. The ____________________ _________________ is the substance that is not used up completely in a reaction.
Guided Practice
1. Silicon dioxide is usually quite unreactive but reacts readily with hydrogen fluoride according to the following
balanced equation.
SiO2(s) + 4HF(g) → SiF4(g) + 2H2O(l)
If 2.0mol of HF are exposed to 4.5mol of SiO2, which is the limiting reactant?
A. SiO2
B. HF
C. SiF4
D. H2O
2-4. The black oxide of iron, Fe3O4, occurs in nature as the mineral magnetite. This substance can also be made in the
laboratory by the reaction between red-hot iron and steam according to the following balanced equation.
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
2. When 36.0g of H2O is mixed with 167g of Fe, which is the limiting reactant?
A. Fe
B. H2O
C. Fe3O4
D. H2
3. What mass in grams of black iron oxide is produced?
4. What mass in grams of excess reactant remains when the reaction is complete?
Independent Practice
5-8 Some rocket engines use a mixture of hydrazine, N2H4, and hydrogen peroxide, H2O2, as the propellant. The reaction
is given by the following balanced equation.
N2H4(l) +2H2O2(l) → N2(g) + 4H2O(g)
5. Which is the limiting reactant in this reaction when 0.750mol of N2H4 is mixed with 0.500mol of H2O2?
A. N2H4
B. H2O2
C. N2
D. H2O
6. How much of the excess reactant, in moles, remains unreacted?
7. How much N2, in moles is formed?
8. How much H2O, in moles is formed?
9-11. Zinc and sulfur react to form zinc sulfide according to the following balanced equation.
8Zn(s) + S8(s) → 8ZnS(s)
9. If 2.00mol of Zn are heated with 1.00mol of S8, identify the limiting reactant.
A. Zn
B. S8
C. ZnS
10. How many moles of excess reactant remains?
11. How many moles of the product are formed?
12-14. Carbon reacts with steam, H2O, at high temperatures to produce hydrogen and carbon monoxide.
12. If 2.40mol of carbon are exposed to 3.10mol of steam, identify the limiting reactant.
A. C
B. H2O
C. H2
D. CO
13. What mass of H2 is formed?
14. What mass of CO is formed?