Limiting Reagent Worksheet
Directions: On a separate sheet of paper, work each of the following problems. I provide clues along the
way. Make sure that you show your work for each problem, and circle your final answer if it is a
calculation.
1.
First, a really simple problem. A person wants to make ham and cheese sandwiches for a picnic.
Each sandwich (Br2Hm3Ch) will be made from two slices of bread (Br), three slices of ham (Hm)
and one piece of cheese (Ch). Write this as a balanced equation.
2.
Using the above equation, if this person has 42 slices of bread, 57 slices of ham, and 29 slices of
cheese, how many sandwiches can be made? How much of the other ingredients will be left over?
So, which substance is completely used up? (That substance will be called the limiting reagent, or
limiting reactant. The limiting reactant is completely used up during a reaction, and this
determines how much of the product can be formed.)
3.
Now for the actual chemistry problems…Suppose you know that sodium chloride can be produced
from the reaction of sodium metal with chlorine gas. Write this as a balanced equation. Check
with me to make sure this is right, because it will affect your answers to questions 4 - 7 after this.
4.
First, a couple regular stoichiometry problems. If you want to make 82.59 g of sodium chloride,
how many grams of each reactant are you going to need?
5.
If you have 25.82 g of sodium metal, how much chlorine should you use to make a complete
reaction?
6.
Now for a limiting reagent problem. If you mix 59.0 g of sodium with 59 g of chlorine gas, which
of these two will be completely used up? (This is called the limiting reactant.) How much of the
excess reactant (the other one that isn’t used up) will be left over? How much sodium chloride
SHOULD be produced? (This amount is called the theoretical yield…the amount of product that
should be produced, based on your calculation. We learned a bit about this in your stoichiometry
lab.)
7.
Based on problem number six, you finish the reaction and measure the amount of NaCl that you
actually have, and the balance says 90.59 g of NaCl, (This number is called the Actual Yield…the
amount of product actually produced.) Using the theoretical yield from problem 6, and the actual
yield from this problem, calculate the percent yield. The formula for percent yield is:
% yield =
actual yield
theoretical yield
x 100
8.
For a reaction of 25 grams copper (II) chloride with 25 grams aluminum, identify the limiting
reactant, calculate the amount (in grams) of the excess reactant left over, and calculate the grams
of each product produced.
9.
OK, only one more. A person has 50 grams of barium chloride and 70 grams of silver (I) nitrate.
How many grams of silver (I) chloride can be produced? Along the way, identify the limiting
reactant and the amount (in grams) of excess reactant left over.