Hr.: ___
Name: _____________________________________
Relating Moles to Coefficient of a Chemical Equation
Unit 9 – Moles Lab 1
Pre-Lab Discussion
The mole is defined as Avogadro’s number (6.02x1023) of particles. These particles may be atoms, molecule, formula
unit, ions, electrons, etc. The concept of the mole is very important, especially when dealing with quantities of solids or
liquids, molar masses are used. The molar mass of a substance is the mass, in grams, of 1 mole of particles of that
substance. When calculating quantities of gases, molar volumes are used. The molar volume is the volume occupied by 1
mole of a gas at STP.
Chemical reactions are represented by balanced chemical equations. Proper interpretation of an equation
provides a great deal of information about the reaction it represents and about the substances involved in the reaction.
For example, the coefficients in a balanced equation indicated the number of moles of each substance. Thus, the ratio of
moles of a substance to moles of any other substance in the reaction can be determined at a glance.
In this experiment, iron filings will be added to an aqueous solution of copper (II) sulfate. A single replacement
reaction will take place, the products being iron (II) sulfate and copper metal. The balanced equation for this reaction is:
Fe(s) + CuSO4(aq)  FeSO4(aq) + Cu(s).
The quantities of iron and copper sulfate used as reactants will be such that the copper sulfate will be in excess.
Thus, the iron will be the limiting factor in determining the number of moles of products that will be formed. As the
equation shows, the number of moles of copper produced should be equal to the number of moles of iron reacted.
This experiment should aid in the understanding of balanced equations and single replacement reactions
Pre-Lab Questions
1. Classify the reaction that will be performed in this lab session.
2. What is an aqueous solution?
3. How do we know that the number of moles of copper produced should be the same as the number of moles of
iron that reacted?
Purpose
Find the ratio of moles of a reactant to moles of a product of a chemical reaction. Relate this ratio to the coefficients of
these substances of the balanced equation for the reaction.
Equipment
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Balance
2 beakers, 100 mL
Graduated cylinder, 50 mL
or 100 mL
Bunsen burner
Ring stand
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Materials
Iron ring
Wire Gauze
Beaker tongs
Glass stirring rod
Safety glasses
Copper sulfate crystals (CuSO4)
Iron filings (Fe)
Safety
Tie back long hair and secure loose clothing when working with a hot plate. Always wear safety glasses when working in
the lab.
Procedure
1. Measure out 8.0 grams of copper sulfate crystals (CuSO4) and add these to a clean, dry beaker. Record
this mass as (a) in your data table.
2. Measure 50.0 mL of water in a graduate cylinder and add it to the crystals in the beaker.
3. Set up a Bunsen burner and ring stand as shown by your teacher. Heat the mixture in the beaker over
the flame using a low setting. DO NOT ALLOW THE LIQUID TO BOIL! While one partner continues to
step 4, the other partner should do step 5.
4. Continue heating and stir the mixture until all of the crystals are completely dissolved. Once all the
crystals are dissolved, USE BEAKER TONGS to remove the beaker from the ring stand and set aside on a
paper towel.
5. Using the balance, measure precisely 2.24 grams of iron filings. Use a weigh boat to hold your sample.
Record this mass as (b) in the data table.
6. Add the iron filings, small amount at a time, to the hot copper sulfate solution. Stir continuously. After
all the iron has been added and the mixture is stirred, allow the beaker to sit for 10 minutes while the
reaction proceeds. Record your observations as (e) in the data table.
7. Decant the liquid into a clean 100 mL beaker as shown below. Be careful not to disturb the solid at the
bottom of the beaker.
8. Add about 10 mL of water to the solid in the 100 mL beaker. Stir vigorously in order to wash off the
solid. Let the solid settle and decant the liquid again.
9. Heat the beaker over a flame for about 4 -- 5 minutes, or until most of the water has boiled off. Using
beaker tongs, set the beaker on a paper towel to cool.
10. Find the mass of a clean weigh boat. Record this mass as (c) in your data table.
11. Scrap as much of your copper product onto the weigh boat. Try not to get any of the water on the
weigh boat.
12. Find the mass of the weigh boat and the copper metal. Record this mass as (d) in your data table.
Observations and Data
a. Mass of copper sulfate
a. _____________________________
b. Mass of iron filings
b. _____________________________
c. Mass of empty weigh boat
c. _____________________________
d. Mass of weigh boat + copper
d. _____________________________
e. Visual observations:
Calculations
Use the following information, as needed, to carry out the calculations. Show all work in the space provided.
𝑚𝑎𝑠𝑠 (𝑔)
# 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 =
𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠
Molar mass for Fe = 55.85 g
Molar mass for Cu = 63.45 g
1. Find the mass of the copper produced:
𝑑−𝑐
2. Find the number of moles of copper produced:
3. Find the number of moles of iron reacted:
4. Find the whole number ratio
𝑚𝑜𝑙𝑒𝑠 𝑖𝑟𝑜𝑛
𝑚𝑜𝑙𝑒𝑠 𝑐𝑜𝑝𝑝𝑒𝑟
Conclusions and Questions
1. How does the ratio found in calculation #4 compare to the ratio of the coefficients of the same two metals in the
balanced equation for the reaction?
2. How many moles of copper sulfate are used to produce the solution in this experiment? Why do you think this
amount of copper sulfate is said to be “in excess”?
3. Explain why the iron is the limiting factor in this experiment.
4. A general description of the single replacement reaction in this experiment is:
metal + salt in solution  “new” metal + “new” salt solution.
Give a balanced equation for another example of this type of single replacement reaction.
5. Give a general description of another type of single replacement reactions.
6. Consider the reaction:
Cu(s) + 2 AgNO3(aq)  2 Ag(s) + Cu(NO3)2(aq)
If 2 moles of copper metal reacts, how many moles of silver metal will be produced?