Objective
Using a chemical reaction between iron and copper(II)
chloride, determine the number of (a) moles of iron that
react and (b) moles of copper produced. Brief Overview
The chemical reaction to be used is this:
Fe(s) + CuCl2(aq) ---> FeCl2(aq) +
Cu(s)
This reaction has a 1:1 mole ratio between iron used and
copper produced. The iron will be provided by two iron nails.
The copper will initially be in the form of Cu2+
ions in solution. (That's what the "aq" means above.)
The iron nails and an empty beaker will be weighed before
the reaction takes place. The nails will be cleaned after the
reaction ceases and then re-weighed. We expect their weight
to go down. The beaker, containing copper metal, will have
the solution decanted and the copper will be washed. Then it
will be dried before weighing.
Once we have the mass of iron used and copper produced, we
will be able to determine the moles of each. With the mole
values, we will be able to verify the ratio of 1:1. Materials List
Equipment
Reagents
250 mL beaker
copper(II) chloride
stirring rod
two iron nails
electric hot plate
10 mL of 1-molar hydrochloric acid
sandpaper
distilled water
electronic balance
Procedure I. Preliminary Steps
Obtain two iron nails and a small piece of sandpaper.
Sand the nails shiny and set them aside. Clean up any
sanding dust on the table with a slightly damp paper
towel.
Use the balance to weigh both nails. Do them together,
not separately and record the mass in the data table.
Using a pencil (no pen please!!) write group member's
names (initials are OK) on the empty 250-mL beaker.
Zero the balance. Weigh the beaker on the balance and
record this value in the data table.
II. Experimental Steps
Part One: Reacting the iron and copper(II) chloride
Put one moderately heaping spoonful of
copper(II) chloride into the 250-mL beaker
Put about 50 mL of
distilled water into the 250-mL beaker. Note: this amount
is approximate. Use the beaker markings (read from the
bottom up) to guide you. Gently swirl the beaker to
hasten solvation.
Place the two nails (nail head down, pointy end up) into
the solution. As you do this, watch the nail surface
closely. Observe the reaction for 2-3 minutes
With more distilled water, fill the beaker to the 150 mL
mark, reading from the bottom up. As the water is added
(slowly enough to have no splashes), use the nails to
stir the solution to dissolve any remaining
CuCl2. Observe the nails for 2-3 minutes.
Allow the nails to sit in the copper(II) chloride
solution undisturbed until next week.
Part Two: cleaning the copper produced
Handle the two nails by the exposed portion, however do
not remove them yet from the solution. Shake off the
copper adhering to the nails. The copper will settle to
the bottom. Rub the two nails together to scrape off as
much copper as possible.
Pull the nails out of the solution and rinse them off,
keeping the rinse water in the beaker. DO NOTrinse
off the nails into the sink. Rinse only with distilled
water.
Set the nails aside on a paper towel and allow to air
dry, then weigh them on the electronic balance. Record
the value in your data table.
Decant the liquid in the beaker while
keeping the solid copper in the beaker. Decant means to pour off a liquid while the solid remains
in the container. Here is how you do it:
Start the water gently running in the sink; it does
not need to be running hard.
Hold a stirring rod in one hand and the beaker in the
other. Use the stirring rod to help keep the copper in the beaker. One person should do the decanting, not two.
Slowly pour the liquid off while trying to keep the
solid undisturbed
Do not pour off the last 5 mL of solution. (The last very small amount). In this
manner, you will minimize the loss of solid during
decanting. Please realize you will lose some solid,
the point is to minimize it.
Add about 20 mL of distilled water to the copper and the remaining 5 mL of water, swirl and let the copper settle. Decant into the sink. Repeat this procedure.
Use the electric hot plate to dry off your copper by boiling off the remaining water. Be careful not to start oxidizing the copper by heating it too long after it is dry!
Part Three: weighing the copper produced
When dry, remove from the heat, allow to cool off and
weigh on the triple beam balance. Record the value in
your data table.
III. Clean-up Steps
With a damp paper towel, clean the copper out of the
beaker. Wrap the copper in more paper towel and throw it
in the trash. Rinse your beaker out with tap water and
leave upside down and wet on the lab table.
Dry the surface of the table and discard all used paper
towels. Return the nails to the box.
Data Table
two iron nails (before)
g
two iron nails (after)
g
250-mL beaker (empty)
g
250-mL beaker (dry copper)
g
DiscussionWrite your answers on a separate piece of paper and reproduce your data table there. Keep this lab packet for future reference.
Determine the grams of iron lost by the nails.
Determine the grams of copper produced.
Calculate the ratio of grams of iron lost to grams of copper produced. (Divide the grams of iron lost by the grams of copper produced).
Calculate moles of iron lost by nails.
Calculate moles of copper produced.
Calculate the molar ratio of iron lost to
copper produced. (Divide the moles of iron lost by the moles of copper produced).
Which of the two ratios that you calculated reflects the chemical relationship shown in the equation at the beginning of this lab?
Why do chemists use moles instead of mass to determine the relationship between chemicals in a reaction?