Anna Xu
Lab 9 Chemistry
Ms. Nakai
Double Replacement Reactions Lab
Problem:
Will the correct ratio between two compounds create the most precipitate?
Hypothesis 1:
If the correct ratio between CaN and NaO is 1:1, than the solution that has that ratio
will be the most precipitate.
Hypothesis 2:
If the correct ratio between Pb(N)3 to NaI is 1:2, than the solution that has that ratio
will be the most precipitate
Experimental Method:
Safety goggles, aprons, and latex gloves were used and chemicals weren’t
dumped into the sink. Before starting the experiment, a table was made to organize
the data, a laptop was prepared to take pictures, and the correct ratios between
different compounds were found by using a balance. In the experiment, we will be
looking for evidence showing precipitate. The independent variable is the different
ratios and the dependent variable is the amount of precipitate. The independent ratio
needs to be balanced, otherwise the experiment isn’t valid.
Before doing the experiment, we balanced out the following equations in order
to determine the correct ratio.
Ca (NO3)2 + Na2 C2O4  Ca C2O4 +Na NO3
The correct ratio is 1:1.
Pb (NO3)2 + 2(Na I)  Pb I2 + 2(Na NO3)
The correct ratio is 1:2
Procedure and Materials: On Lab sheet attached below
Anna Xu
Lab 9 Chemistry
Ms. Nakai
Data Collection:
Table 1
Ratio of CaNO3 to NaC2O4
1 to 9
2 to 8
3 to 7
4 to 6
5 to 5
6 to 4
7 to 3
8 to 2
9 to 1
Color
milky white
more milky white
more milky white
more milky white
more milky white
less milky white
less milky white
less milky white
less milky white
Odor
no odor
no odor
no odor
no odor
no odor
no odor
no odor
no odor
no odor
Precipitate
Little precipitate
More precipitate
More precipitate
More precipitate
Quite precipitate
Less precipitate
Less precipitate
Less precipitate
Little precipitate
other
gas is released
gas is released
gas is released
gas is released
gas is released
gas is released
gas is released
gas is released
gas is released
Table 2
Ratio of Pb(NO3)2 to
NaI
1 to 9
2 to 8
3 to 7
4 to 6
5 to 5
6 to 4
7 to 3
8 to 2
9 to 1
Color
turns solid yellow
turns solid yellow
turns solid yellow
turns solid yellow
turns solid yellow
turns solid yellow
turns solid yellow
turns solid yellow
turns solid yellow
Odor
no odor
no odor
no odor
no odor
no odor
no odor
no odor
no odor
no odor
Precipitate
Little precipitate
More precipitate
Quite precipitate
Quite precipitate
Less precipitate
Less precipitate
Less precipitate
Less precipitate
Little precipitate
other
gas is released
gas is released
gas is released
gas is released
gas is released
gas is released
gas is released
gas is released
gas is released
Anna Xu
Lab 9 Chemistry
Ms. Nakai
Data Processing:
Pictures 1:
Gathering materials
Dropping in Calcium
Nitrate
Dropping in Sodium Oxalate
Testing Precipitate
Looking for heat
Flipping the solution upside
down
Pictures 2
Dropping Sodium Iodide
into lead Nitrate
Dropping Sodium Iodide
into lead Nitrate
Dropping Sodium Iodide
into lead Nitrate
Completing the dropping
process
Testing Precipitate
Flipping the solution upside
down
Anna Xu
Lab 9 Chemistry
Ms. Nakai
Evaluation:
My hypothesis was correct. When the perfect ratio is balanced, the solution
becomes very precipitate. My results in the first test seem to show that the ratio of
1:1, shown when we mixed 5 drops of Calcium Nitrate and Sodium Oxalate, was the
most precipitate compared to all of the other solutions. In the second test, the solution
with the ratio closest to the perfect ratio, 3 drops of Lead Nitrate to two drops of
Sodium Iodide, was the most precipitate compared to the others.
The reason that the solution will become more precipitate when the perfect
ratio is formed is because the two solutions bond together better. They then leave the
left over solution that can’t bond due to not having the correct ratio at the top of the
test tube.
When dropping in any of the liquids, water or chemicals, not everybody was
watching and counting, therefore there could be some areas that weren’t as precise as
other areas, which causes the accuracy to lower. Also, not all of the drops were
exactly the same size. There could have been larger drops and smaller drops.
Because of the human mind’s lack of perfection, it would take many human
minds to make sure that everything was done accurately. If one of the substances had
an extra drop of water or a different chemical, it would create inaccurate results. If
some of the drops weren’t as large or as small as other drops, it would also create
inaccurate results.
If I were to do this experiment another time, I would have many people
watching and making sure the number of drops was accurate. I also would have one
person do the drops because the amount of pressure used to squeeze a bottle is
different for everyone.