Stoichiometry
•
Purposes: to explore single displacement and double displacement reactions; to learn
about the basis of stoichiometry, i.e. the quantitative nature of chemical equations, and
the experimental basis of numerically balancing equations.
Note: you will predict the products of various single and double displacement reactions, as
well as write and balanced formula equations for each reaction.
•
Hypothesis
1
•
Materials
Chemicals
Hardware
Part I
Single
displacement
reactions
Zinc, metal
Aluminum, metal
Copper, metal
Magnesium, metal
Hydrochloric acid 1M
Nitric acid 1M
Sulfuric acid 1M
24-well micro-plate
Forceps
Pipette
Part II
Double
displacement
reactions
0.1 M solutions of…
Group A:
Copper (II) Nitrate
Nickel (II) Nitrate
Lead (II) Nitrate
Cobalt (II) nitrate
nitric acid
silver nitrate
aluminum nitrate
iron (III) nitrate
96-well micro plate
Pipettes
Group B:
Sodium carbonate
Sodium sulfate
Ammonium hydroxide
Sodium chloride
EDTA
Sodium Iodide
Sodium thiocyanate
Sodium chromate
Sodium dichromate
Sodium hydroxide
Demineralized water
Part III
Reaction
coefficients of
double
displacement
reactions
Lead nitrate 0.1M
Sodium iodide 0.1M
Demineralized water
Calcium nitrate 0.1M
Sodium oxalate 0.1M
96-well micro-plate
Pipettes (3)
White paper
Black paper
Toothpicks
2
•
Procedures
1. Part 2
1.1. Place the 24-well micro plate on a piece of white paper, and label the rows and columns
as below with the formula of the acids across the top and the metals along the side.
Hydrochloric
Nitric
Sulfuric
Al
Zn
Cu
Mg
1.2. Using forceps, place a piece of Al metal in each cell in row 1. *The Al strip should be
sanded and wiped clean first. Continue by placing a piece of Zn in each cell in row 2, a
piece of Cu in each cell in row 3, and a piece of Mg in each cell in row 4. The metal
pieces should be ½” long
1.3. Predict what products might be formed when each acid is carefully added to each cell in
columns 1, 2, and 3. Before adding the acids, not only predict the possible products of
each combination, but also write and balance a formula equation representing each
combination. Record this information in Table 1a.
1.4. Now verify your predictions by adding 6 drops of hydrochloric acid to each well in
column 1. Observe and record your observations in Table 1b. After rinsing the pipette,
transfer 6 drops of nitric acid to each well in column 2. Again record your observations
in Table 1. Lastly, after again rinsing the pipette, transfer 6 drops of sulfuric acid to each
well in column 3. Record your observations in table 1c. Did all react? If not, can you
suggest a reason why not?
1.5. Write a completed and balanced equation for all the reactions that did occur. Record this
information in Table 1b. Indicate whether a gas, a precipitate, heat or color change
occurred as the indication of reactivity. Also note where no noticeable change place. Do
you think time would have an effect on the reactivity of these combinations? What might
be done to encourage reactivity?
3
Data tables for part 1
Table 1a: predictions
Will the reaction take
place?
Predict the products
Al +
hydrochloric
acid
Zn +
hydrochloric
acid
Cu +
hydrochloric
acid
Mg +
hydrochloric
acid
Al + nitric acid
Zn + nitric acid
Cu + nitric acid
Mg + nitric acid
Al + sulfuric
acid
Zn + sulfuric
acid
Cu + sulfuric
acid
Mg + sulfuric
acid
4
Table 1b: observations
Observations
Al + hydrochloric acid
Zn + hydrochloric acid
Cu + hydrochloric acid
Mg + hydrochloric acid
Al + nitric acid
Zn + nitric acid
Cu + nitric acid
Mg + nitric acid
Al + sulfuric acid
Zn + sulfuric acid
Cu + sulfuric acid
Mg + sulfuric acid
5
Table 1c: balanced chemical equations
Balanced chemical equation
Al + hydrochloric acid
Zn + hydrochloric acid
Cu + hydrochloric acid
Mg + hydrochloric acid
Al + nitric acid
Zn + nitric acid
Cu + nitric acid
Mg + nitric acid
Al + sulfuric acid
Zn + sulfuric acid
Cu + sulfuric acid
Mg + sulfuric acid
6
2. Part 2: double displacement reactions
2.1. The objective of this experiment is to mix each of the reagents listed above from
Group A, with each of the reagents from Group B. Arrange the 9-well micro plate so
that the lettered rows are on the left and the numbered columns are at the top.
2.2. Place 4 drops of copper (II) nitrate in each of the numbered wells in row A. after rinsing
your pipette, fill the wells in Row B with 4 drops of nickel (II) nitrate. Rinse your pipette
again and continue in a similar manner using all of the solutions from Goup A.
2.3. When all of the rows have been given the particular reagent assigned from Gropup A,
begin to add 4 drops of each of the reagents from Group B, one reagent to each column.
Rinse your pipette between samples so that contamination does not occur. For example,
sodium carbonate is added to each well in column 1; sodium sulfate is added to each of
the wells in column 2, and so on. In this way each of the compounds in Group A is
mixed with each of the compounds in Group B.
2.4. In Table 2a below, record any combination which showed any form of reactivity and
indicate the form of that activity (e.g., gas, precipitate, color change, etc.)
2.5. In Table 2b, write and balance a double displacement equation for each of the
combinations that showed any type of reactivity. You will have to predict the products,
as in Part 1.
7
Table 2a.Observations
Sodium
Sodium
carbonate sulfate
Ammonium
hydroxide
Sodium
chloride
EDTA
Sodium
iodide
Sodium
Sodium
thiocyanate chromate
Sodium
Sodium
Demineraldichromate hydroxide ized water
A. Nickel (II)
Nitrate
B. Lead (II)
Nitrate
C. Cobalt (II)
Nitrate
D. Nitric Acid
E. Silver
Nitrate
F. Aluminum
nitrate
G. Iron (III)
Nitrate
8
Table 2b: balanced chemical equations
Balanced chemical equation
A. Nickel (II) Nitrate
Nickel (II) Nitrate +
Sodium carbonate
Nickel (II) Nitrate +
Sodium sulfate
Nickel (II) Nitrate +
Ammonium hydroxide
Nickel (II) Nitrate +
Sodium chloride
Nickel (II) Nitrate +
EDTA
Nickel (II) Nitrate +
Sodium iodide
Nickel (II) Nitrate +
Sodium thiocyanate
Nickel (II) Nitrate +
Sodium chromate
Nickel (II) Nitrate +
Sodium dichromate
Nickel (II) Nitrate +
Sodium hydroxide
Nickel (II) Nitrate +
Demineralized water
B. Lead (II) Nitrate
Lead (II) Nitrate +
Sodium carbonate
Lead (II) Nitrate +
Sodium sulfate
Lead (II) Nitrate +
Ammonium hydroxide
Lead (II) Nitrate+
Sodium chloride
Lead (II) Nitrate +
EDTA
9
Lead (II) Nitrate +
Sodium iodide
Lead (II) Nitrate +
Sodium thiocyanate
Lead (II) Nitrate +
Sodium chromate
Lead (II) Nitrate +
Sodium dichromate
Lead (II) Nitrate +
Sodium hydroxide
Lead (II) Nitrate +
Demineralized water
C. Cobalt (II) Nitrate
Cobalt (II) Nitrate +
Sodium carbonate
Cobalt (II) Nitrate +
Sodium sulfate
Cobalt (II) Nitrate +
Ammonium hydroxide
Cobalt (II) Nitrate +
Sodium chloride
Cobalt (II) Nitrate +
EDTA
Cobalt (II) Nitrate +
Sodium iodide
Cobalt (II) Nitrate+
Sodium thiocyanate
Cobalt (II) Nitrate +
Sodium chromate
Cobalt (II) Nitrate +
Sodium dichromate
Cobalt (II) Nitrate +
Sodium hydroxide
Cobalt (II) Nitrate +
Demineralized water
D. Nitric Acid
10
Nitric Acid + Sodium
carbonate
Nitric Acid + Sodium
sulfate
Nitric Acid +
Ammonium hydroxide
Nitric Acid + Sodium
chloride
Nitric Acid + EDTA +
Sodium iodide
Nitric Acid + Sodium
thiocyanate
Nitric Acid + Sodium
chromate
Nitric Acid + Sodium
dichromate
Nitric Acid + Sodium
hydroxide
Nitric Acid +
Demineralized water
E. Silver Nitrate
Silver Nitrate + Sodium
carbonate
Silver Nitrate + Sodium
sulfate
Silver Nitrate +
Ammonium hydroxide
Silver Nitrate + Sodium
chloride
Silver Nitrate + EDTA
Silver Nitrate + Sodium
thiocyanate
Silver Nitrate + Sodium
chromate
Silver Nitrate + Sodium
dichromate
11
Silver Nitrate + Sodium
hydroxide
Silver Nitrate +
Demineralized water
F. Aluminum nitrate
Aluminum nitrate +
Sodium carbonate
Aluminum nitrate +
Sodium sulfate
Aluminum nitrate +
Ammonium hydroxide
Aluminum nitrate +
Sodium chloride
Aluminum nitrate +
EDTA
Aluminum nitrate +
Sodium iodide
Aluminum nitrate +
Sodium thiocyanate
Aluminum nitrate +
Sodium chromate
Aluminum nitrate +
Sodium dichromate
Aluminum nitrate +
Sodium hydroxide
Aluminum nitrate +
Demineralized water
G. Iron (III) Nitrate
Iron (III) Nitrate +
Sodium carbonate
Iron (III) Nitrate +
Sodium sulfate
Iron (III) Nitrate +
Ammonium hydroxide
Iron (III) Nitrate +
Sodium chloride
12
Iron (III) Nitrate +
EDTA
Iron (III) Nitrate +
Sodium iodide
Iron (III) Nitrate +
Sodium thiocyanate
Iron (III) Nitrate +
Sodium chromate
Iron (III) Nitrate +
Sodium dichromate
Iron (III) Nitrate +
Sodium hydroxide
Iron (III) Nitrate +
Demineralized water
13
3. Reaction coefficients
3.1. The objective of this exercise is to help you understand the concept of the balancing
coefficient.
3.2. Place the 96-well micro plate on the black paper. (Note the numbering on the plate. The
wells have numbered columns 1-12 left to right, and rows A to H top to botrtom.) add 4
drops of water to each of the top row of wells. This will be the row to sue through the
experiment.
3.3. Add 1 drop of calcium nitrate to well #1, 2 drops to #2, 3 drops to #3, and so on until
you finish with well #90. Rinse your pipette.
3.4. With a clean pipette, repeat the procedure above, adding drops of socium oxalate to the
wells in the same manner, BUT IN REVERSE ORDER. That is, 1 drop of socium
oxalate is added to well #9, 2 drops to well #8, 3 drops to well #7 and so on until #1
contains 9 drops of the sodium oxalate solution.
3.5. Mix each of the wells with a toothpick. Allow five minutes for a completed reaction to
occur.
3.6. While waiting, calculate and record the ratios from each of the wells in table 3a, using
the following formula:
Ratio = # for the drops of calcium nitrate / # drops of sodium oxalate
3.7. Which of the wells has the largest amount of precipitate?
What is the ratio of coefficients in the balanced equation?
How does this ratio compare to the ratio you found by experimentation?
3.8. Write a balanced formula equation for the reaction. How does your calculated ratio
compare to the ratio found by experimentation?
3.9. Repeat the procedure in 3.2-3.8, with the following changes
3.9.1. Use white paper to set the micro plate on.
3.9.2. Add 4 drops of water to each of the top row of wells.
3.9.3. Add lead nitrate to each well in the row starting with well #1 and proceeding to
the right (take care to add the correct number of drops to each well, as instructed in
step #3.
3.9.4. Figure the ratio of reactants as follows, and record them in row 1 of table 3:
ratio = #drops of lead nitrate : # drops of sodium iodide
3.9.5. Write a balanced formula equation for the reaction.
3.9.6. Again, which of the wells has the largest amount of precipitate?
What is the ratio of coefficients in the balanced equation?
How does this ratio compare to the ratio you found by experimentation?
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1
2
3
4
5
6
7
8
9
Ratio s of
calcium nitrate
: sodium
oxalate
Ratios of lead
nitrate :
sodium iodide
15