Le Chatelier's Equilibrium Lab
20 points
Purpose:
To illustrate the
properties of Le Chatelier's Principles of Equilibrium
Pre-Lab
Questions: (4 points)
1. If a reaction is endothermic, what should
you do to the reaction to
shift
the equilibrium to favor the products?
a. Heat it b.
Cool it
2. If a reaction is exothermic, what should you
do to the reaction to shift the equilibrium to
favor
the products? a. Heat it.
b. Cool it.
3. Several ways to favor the products of a
reaction is to (select the TWO
correct
answers): a.
add more reactants b. add more products c. remove reactants
d. remove products.
4. Name at least two visual indications you can see during a reaction to see if a
reaction is
shifting
to favor either the products or the reactants.
5. Name at least four things you can do to affect the rate at which a reaction
occurs.
6. How would you write the Keq for the
following reaction:
Fe3+(aq)
+ SCN- (aq) <----> FeSCN2+ (aq) (FeSCN2+ Is a Dark Red Color.)
7. How would you write the Keq for
the following reaction:
Co(H2O)62+
(aq) + 4Cl- (aq) + energy
<------> CoCl42-
(aq) + 6H2O(l)
8. Is the reaction in pre-lab question #7 endo
or exothermic?
9. If the Keq value for the equation
in #7 is 1.75 L4/mole4, does that mean
the equilibrium of
this reaction favors the products or
favors the reactants?
Materials:
Plastic
Well Plate
White
Sheet of Paper
MicroPipette USE
THE MICROPIPETTE IN PROCEDURE PART II ONLY!!!!!!!!!!!!
Procedure
Part I:
1. In four empty wells of the well plate, place
enough FeCl3 and KSCN to fill the wells
to
about 1/2 full. Use an equal amount of
drops of FeCl3 as you do KSCN.
2. To each of these four wells, add 5-6 drops
of the following chemicals: (add only
one
type
of each chemical to each well).
IMPORTANT: REMEMBER WHICH WELL
GOT
WHICH
CHEMICAL ADDED TO IT!!!!!!!!!!!!!!!
Iron
(II) nitrate
Potassium
Bromide
Sodium
Carbonate
Sodium
Hydroxide
3. Record the color change after the addition
of each one of these chemicals in your data
table. The choices you will have for color change
are: "Turns
yellowish/clear", "Turns More
Red",
"No
Change"
4. Rinse all of this down the sink and dry out
your well plates.
Data
Table: (2 point)
Chemical
added Color Change
Iron (II) nitrate _______________
Potassium Bromide _______________
Sodium Carbonate _______________
Sodium Hydroxide _______________
Questions: (6 points)
1. Which one(s) of these chemicals that you
added made the reaction shift more to the
right?
2. Why did this/these chemicals shift the
reaction to the right?
3. What visual clue did you have that the
reaction was shifting to the right?
4. Look at page 900 (or p. 427 Table 14-1) and
explain why the other chemicals did
what
they did to this reaction: (these are
the chemicals which either caused "No Change" or
"Turns
yellowish/clear".) Show your
answers as you see them written below - use a full sentence.
Name of Chemical: Why did it
have this effect?
______________________
___________________________________
______________________ ____________________________________
______________________ ____________________________________
Procedure
Part II:
1. Make an ice water bath in a 150 mL
beaker.
2. Make a hot water bath in a 150 mL beaker on
a hot plate.
3. Fill one well plate well 1/2 way full with
CaCl2 pellets.
4. Add enough Cobalt (II) chloride to the same
well to fill it almost to the tippy top.
5. Use your plastic pipette to stir the
solution until all of the CaCl2 pellets are dissolved in the
solution.
6. If your solution is now purple, you can go
on to step #7. If it is still pink,
please add some more CaCl2
until the solution is
purple.
7. Draw up the entire contents of the well into
the micropipette BULB. This means that
the entire contents of
the well plate should
be in the BULB of the pipette, not the stem.
8. Submerge the bulb of the micropipette
alternately into the hot water and the cold water. Record the color
change you get in the
hot water vs. the color change you get in the cold water on your data table.
Data
Table: (2 point)
Color
of solution in Hot Water:
______________________
Color
of solution in Cold Water:
______________________
Questions: (6 points)
1. Use the information provided
in the pre-lab to determine which color is associated with which chemical.
Chemical Color
Co(H2O)6
2+(aq) ___________
CoCl4
2-(aq) ___________
2. COPY THE FOLLOWING SENTENCE
EXACTLY AS YOU SEE IT HERE ONTO YOUR LAB WRITE UP. SIMPLY CHOOSE THE CORRECT WORDS WHERE UNDERLINED AND BOLDED:
“The Keq of this reaction is 1.75 L4/mole4
at room temperature. This means that
the reaction favors the PRODUCTS/REACTANTS
at room temperature. Since the color of
the solution at room temperature was PURPLE/PINK,
we know that Co(H2O)6
2+(aq)/ CoCl4 2-(aq)
was the chemical of that color because that chemical is on the PRODUCTS/REACTANTS side.”
3. Use the sentence format you
see in question #2 to answer this: How
did the placement of the word “energy” in the original balanced equation help
you determine which chemical belonged with which particular color as you
performed the experiment? (example
answer: “Because “energy” is on
the…………………..etc”).