Alexander Huang
Nakai Lab Science 9
Double Displacement Ratios Lab Report
Initial Problem:
What ratio of two ionic compounds will create a final product with the best
possible properties?
Hypothesis:
If an ionic compound is mixed with an equal amount of a second ionic compound
(a 1-to-1 ratio), then the two compounds will react in the best possible way to
form two new substances because when there is a 1-to-1 ratio between two
compounds in double replacement, all parts of both compounds take place in the
reaction.
Experimental Method:
After a brief study of ratios and double displacement over the Internet, the
hypothesis was formed based on a series of personal observations and factual
evidence.
Using resources given by the lab instructor and supervisor, data on the
procedure of a double displacement reaction were discovered. Double
displacement reactions occur when two substances—covalent or ionic
compounds consisting of two different types of elements or molecules—that
tend to react with each other and mixed together. One of the elements in each
compound breaks off and attaches onto the other in a “displacement” act. The
result is two new substances with completely different properties. The common
formula for a double displacement reaction is as follows:
AB + CD  AD + CB
When considering the double displacement formula, understand that each letter
represents an element, molecule or compound (for example, Oxygen [O], air [O2],
or Nitrate [NO3]). Therefore, in total, there are four variables: A, B, C and D.
After an analysis of the double displacement formula combined with an
understanding of ratios, it seems evident that if one places a single element in
each of the variables, then the result will yield absolutely no remainder. For
example, mathematically, if one were to put a 1 into each variable, the end result
will end up being as the reactants, thus balancing out perfectly. Thus the
hypothesis was created.
Additional information needed in the experiment lied within the concept of
balancing equations. According to the Law of Conservation of Mass, matter can
be neither created nor destroyed. This means that there must be the same
amount of elements in the reactant(s) and the product(s). Balancing an equation
refers to the act of adding coefficients to compounds in order to achieve the
same amount of elements in both sections yet still prove the chemical reaction
correct.
Alexander Huang
Nakai Lab Science 9
The lab experiment will involve two sub-experiments between two ionic
compounds: Calcium Nitrate and Sodium Oxalate, and Lead Nitrate and Sodium
Iodide.
In the hypothesis and the
overall experiment, the
ratio is the independent
variable, and the reaction
is the dependent variable.
This indicates that during
the experiment, the ratio
will be changing the
result of the reaction (if
there is a change).
The control of this
experiment is each of the
four compounds by
Calcium Nitrate before Sodium Oxalate was added to the
themselves. Each control experiment. It looks just like water from this point of view.
had about the same
chemical properties from human perspective; they each had generally a clear
color, it had no odor, and it was at room temperature. It is important to know
what the original properties of the substance looks like when determining the
effectiveness of a chemical reaction, so controls are used. Due to conservation
purposes, the controls were not dropped directly into any well.
In order to prove that a chemical reaction indeed occurred when two of the
above compounds mixed together, a basic “Evidence for Chemical Reactions” list
was used in conjunction with the experiment. The list is as follows:
Evidence for Chemical Reactions







A gas is released.
An insoluble substance is produced.
A permanent color change is observed.
A heat energy change is noted.
(exothermic reaction: releases heat)
(endothermic reaction: absorbs heat)
(Light is emitted)
Before the experiment, is it expected that each experimenter should equip
themselves with safety goggles and aprons in order to ensure well-being during
the experiment (should anything go wrong). It would also be wise to understand
the chemical formula of each compound:
Calcium Nitrate: Ca(NO3)2
Sodium Oxalate: Na2C2O4
Lead Nitrate: Pb(N3)2
Sodium Iodide: NaI
Alexander Huang
Nakai Lab Science 9
As said above, the experiment will be composed of two parts: the mixing of
Calcium Nitrate and Sodium Oxalate, and the mixing of Lead Nitrate and Sodium
Iodide. During the experiment, four drops of demineralized water will be placed
into nine different wells. Then, one compound (so, in the first experiment,
Calcium Nitrate) is dropped using a pipette from left to right, with one drop into
the first well, two drops into the second well, continuing in this fashion until nine
drops are dropped into the 9th well. Then, the second compound (following
Calcium Nitrate, Sodium Oxalate) will follow the same dropping pattern as the
first compound, except that it will be dropped in reverse order (meaning one
drop in the 9th well, two drops in the 8th well, etc). The ending result will be nine
different wells with nine different ratios of the two compounds.
Procedure:
The above image was taken directly from the official experiment sheet. Please
note that the experiment requires only one sheet of white paper and one sheet of
black paper, but nine toothpicks (for best results). There needs to be a minimum
of seventy-four drops of water (a 250mL bottle of de-mineralized water would
be more than enough).
The procedure is as follows:
1. Take the black sheet of paper and place it on the lab table. Place the 96well micro plate on top of the black paper.
2. Add four drops of de-mineralized water to the first row’s nine wells using
a pipette.
3. Using a second pipette, take one drop of Calcium Nitrate and add it to the
first well (1A). Then add two drops of Calcium Nitrate to Well 2, three to
Well 3 and so on until you add nine drops to Well 9.
4. With a third pipette, use the same manner to add drops of Sodium Oxalate
into wells, except in reverse order. That means one drop of Sodium
Oxalate into Well 9, two drops in Well 8 and so on until you add nine
drops to Well 1.
5. Mix each of the wells with a toothpick (for best results use one toothpick
per well, so no excess molecules are added to any well).
6. While waiting for the reaction to complete, make a table of the ratios from
each of the wells (1:9 for the first well, 2:8 for the second, etc).
Alexander Huang
Nakai Lab Science 9
7. After five minutes, examine wells. Write observations and evidence for
each ratio.
8. Make a table of the ratios, the observations and the evidence for Calcium
Nitrate and Sodium Oxalate.
9. Balance the reaction, which is Ca(NO3)2 + Na2Ca2O4  CaC2O4 + NaNO3
and keep note of the ratio of the coefficients of the balanced equation.
The procedure for the second experiment (the one with Lead Nitrate and Sodium
Iodide) is very similar:
10. Take the white sheet of paper and place it on the table. Place the 96-well
micro plate on top of the white paper.
11. Add four drops of de-mineralized water to the second row’s nine wells
with a clean pipette.
12. Using a second pipette, take one drop of Lead Nitrate and add it to the
first well (1B). Use the pattern in Step 3 above; add one drop of Lead
Nitrate to the first well, two to the second, and so on until nine drops are
added to Well 9.
13. With the third pipette, take a drop of Sodium Iodide and add it to Well 9.
Follow the pattern in Step 4; add one drop of Sodium Iodide to the ninth
well, two to eighth, and so on until nine drops are added to the first well.
14. Write observations and evidence for each of the ratios in the second
experiment.
15. Make a table of ratios, observations and evidence for Lead Nitrate and
Sodium Iodide.
16. Balance the reaction, which is Pb(N3)2 + NaI  PbI2 + NaNO3, and keep
note of the ratio of the coefficients of the balanced equation.
No stirring is needed for the second experiment, but waiting a while for the
reaction to complete is suggested.
Alexander Huang
Nakai Lab Science 9
Data Collection
In the above table, the different ratios of each well are shown, with observations
in the “Evidence” section and conclusions in the “Observations” section. Take
note that in each ratio, the first number refers to the drops of Calcium Nitrate in
the overall compound, while the second number refers to the number of drops of
Sodium Oxalate.
According to the graph, it
appears that the properties
of the substance remain
exactly the same – every well
was cohesive, milky white,
and foggy, with a precipitate
formed and its temperature
colder than the reactants.
The only noticeable
difference between each
ratio is each property’s
intensity within the
substance.
The equation Ca(NO3)2 +
The results of Calcium Nitrate and Sodium Oxalate –
milky, foggy substances that do not fall when flipped
upside down – just like the Dairy Queen™ Blizzard!
Alexander Huang
Nakai Lab Science 9
Na2Ca2O4  CaC2O4 + NaNO3 could be balanced out by simply adding the
coefficient “2” after NaNO3. With that coefficient in place, the equation abides by
the Law of Conservation of Mass.
For the ratios of the second table, the first number is the number of drops of
Lead Nitrate into a given well, while the second drop is the number of drops of
Sodium Iodide into a given well.
Much like the first experiment, the properties of each ratio was not different, but
in different intensities. As seen in the photo, each substance is yellow, opaque,
and cohesive, but the tone of each yellow is slightly different depending on its
ratio.
For the balancing of the second equation (Pb(NO3)2 + NaI  PbI2 + NaNO3), it
was discovered that there needs to be a coefficient in front of NaI and NaNO3 to
abide by the Law of Conservation of Mass.
The result of the mixing of Lead Nitrate and Sodium Iodide in the
second row of the microplate (the first row still containing the first
experiment). Looks like this is how they make LEGO™s.
Alexander Huang
Nakai Lab Science 9
Data Processing
It is absolutely vital to remember the overall aim of the experiment while
processing the data. The experiment’s purpose is to see which ratio of ionic
compounds will create the most complete reaction in the double displacement
reaction. The experiment is more about observations, patterns and ratios than
exact numbers, trends and other mathematical equations.
According to the Evidence for Chemical Reactions list, a reaction has occurred
within all wells of the first experiment because the color has been changed, a
temperature change is apparent, and a precipitate was formed (not shown in the
image).
It is evident that all properties remain the same. However, as said in the
description of the table, each ratio of the experiment had a different intensity of
the reaction. For now, it is believed that the biggest reaction is the most complete
reaction, because it made the most out of it with the same number of drops (each
well had a total of ten drops in it). Looking at the observations made during the
experiment and the image of the experiment itself, it is apparent that the middle
three wells (the 4:6 ratio, 5:5 ratio, and 6:4 ratio, or wells 4, 5 and 6) are the
milkiest and foggiest. However, in well #5 (5:5 ratio), the substance is so foggy to
the point of nearly being opaque; thus, from the naked eye, the ratio 5:5 – which
can be simplified to a 1:1 ratio – is the most complete reaction.
This assumption can be confirmed by looking into the double displacement
equation of Calcium Nitrate and Sodium Oxalate. The double displacement
formula for Calcium Nitrate and Sodium Oxalate is given: Ca(NO3)2 + Na2Ca2O4 
CaC2O4 + NaNO3. During the experiment, it was discovered by adding the
coefficient “2” in front of NaNO3, the equation would be balanced. Thus the ratio
of the first experiment is 1:1  1:2. A 1:1 ratio is the closest ratio to match this
balanced equation.
The second experiment is a chemical reaction because of a permanent color
change. The change in color is considered a chemical change in this experiment
because it is difficult to mix two clear substances together and physically obtain
a yellow color.
The result of the Lead Nitrate and Sodium Iodide experiment is very much like
the result of the Calcium Nitrate and Sodium Oxalate one. It’s a bit difficult to see
it in the image, but the 5:5 ratio (5th well) has the darkest tone of yellow among
the others.
The chemical equation for Lead Nitrate and Sodium Iodide (Pb(NO3)2 + NaI 
PbI2 + NaNO3) is balanced by adding the coefficient 2 in front of NaI and NaNO3.
This makes the ratio of the second experiment 1:2  1:2. This shows that the
total amount of molecules in the experiment (each number is a molecule)
Alexander Huang
Nakai Lab Science 9
remains the same (3), meaning that if a 1:1 ratio were to occur, it would close to
a perfect reaction.
Evaluation
The hypothesis is proven correct because in both sub-experiments, the 1-to-1
ratios had the best reaction among all nine ratios.
The original hypothesis of the experiment was that if there were equal amounts
of drops from both ionic compounds in a double displacement experiment, then
the reaction would yield the biggest and best results. According to the data taken
from the experiment, the 1-to-1 ratio had the most intense change in properties
(see Tables 1 and 2, ratio 5:5). The processed results of the experiment also
seem to show that among all nine possible ratios, the 1-to-1 ratio yields the best
reaction. This assumption is proven by the balancing of equations and the
discovery of the ratios of the coefficients in each formula. The results of the
experiment and the processed data both prove the hypothesis correct.
It seems straightforward to assume that one drop of a substance will mix with
exactly another drop of a second substance, and the balancing of the equation
proves it. In the first Calcium Nitrate and Sodium Oxalate experiment, a 1:1 ratio
creates the perfect reaction, as there is one drop of both compounds mix
together perfectly to form three molecules. In the second experiment, there is a
1:2 ratio, which would roughly translate to a 3.33:6.67 reaction (out of 10
drops). The closest to achieve this “perfect” ratio as a whole number still lies
within the 1:1 threshold. Thus, it is safe to conclude that a 1:1 ratio would
generally give the best reaction.
Some of the mistakes that have been made during the experiment was that the
procedure was done only once, the pipettes were not thoroughly cleaned, and
the wells were not all stirred properly. The procedure’s results were quite
similar in properties; it took close observations to tell a difference. Perhaps this
is the general case in the experiment, but verification would be ideal. In addition,
the pipettes were not thoroughly cleaned after the first experiment was
completed, meaning that excess Calcium Nitrate, Sodium Oxalate or water
molecules may have altered the second experiment. Lastly, it took around thirty
seconds to one minute before one experimenter discovered the failure to stir
each well with a toothpick. This could have resulted in some errors in data
collection.
The design of the experiment could have been a lot more organized and wellconstructed. Some of the mistakes made during the experiment could easily have
been avoided, such as properly cleaning the pipettes between each experiment.
The 96-well microplate has eight rows; with these eight rows, it is possible to
conduct eight experiments, or a maximum of four recreations. The experiment
could also have been expanded to a total of eleven drops instead of nine.
The understanding of double displacement reactions and ratios flourished
during and after experiment. It allowed experimenters to learn the art of
Alexander Huang
Nakai Lab Science 9
balancing equations, the idea of double displacement reactions, and the
implementation of ratios into science.