FEB 18, 2015
SNC 2DI-03
CHCI
[Your Name]
Partners: [Your Partner(s)]
Teacher: Mr. C. Busch
INV # The Effect of the Mass of Reactants on the
Mass of Products using Iron Nitrate and Sodium
Hydroxide
Purpose:
The purpose of this investigation is to…
Question:
Does changing the mass, in grams (g), of the reactants have an effect on the
mass (g) of the products of a chemical reaction, using iron nitrate solution and
sodium hydroxide solution?
Hypothesis:
If the mass of the reactants is successively increased, then the mass of the
products will increase more than the reactants when a precipitate is formed,
but less than the reactants when a gas is formed. These results are expected
because…
or
If the mass of the reactants is successively increased, then the mass of the
products will increase by the same amount such that the mass of reactants is
always equal to the mass of the products, because the same atoms are
rearranged from reactants into products.
Variables:
 The independent variable is the mass of the reactants of a chemical reaction.
 The dependent variable is the mass of the products of the reaction.
 Important controlled variables include the: type of chemical reaction,
temperature, reaction chamber, states of reactants (and products). The type
of reaction will be controlled by using the same reactants for each trial: iron
nitrate solution and sodium hydroxide solution. The temperature will be
kept the same by conducting the reaction at room temperature. The reaction
chamber will be kept sealed. The same chemicals will be used for all
reactions, so the states will also stay the same for each trial. Similarly, a
graduated cylinder will be used for volume measurements.
Materials:
 16 mL iron (III) nitrate solution
 50 mL sodium hydroxide solution
 250 mL Erlenmeyer flask
 10mL test tube (that fits inside the 250 mL flask)
 safety goggles
 rubber stopper (to fit the 250 mL flask)
 electronic balance
 10 mL graduated cylinder
 thermometer
 waste container
 paper towels
 ruler
Method/Procedure:
1. Put on safety goggles, as sodium hydroxide is corrosive.
2. Using a thermometer, measure the temperature of the room.
3. Using the graduated cylinder, add 10 mL of sodium hydroxide into the
flask.
4. Rinse the graduated cylinder thoroughly with tap water and dry it with a
paper towel.
5. Using the graduated cylinder, add 4 mL iron nitrate into the test tube,
and place the test tube gently into the flask.
6. Place the stopper securely in the flask.
7. Observe and record the physical properties of the solutions.
8. Using the electronic balance, measure the mass of the reactants
(including the equipment). Record the mass in grams.
9. Tip the flask so that the solutions mix.
10. Using the electronic balance, measure the mass of the products
(including the equipment). Record the mass in grams.
11. Observe and record the physical properties of the products.
12. Empty the flask and test tube into the waste container, thoroughly rinse
the equipment with tap water and dry it with paper towels.
13. Repeat steps 3-12 for a total of 3 trials, by recording two other groups’
data.
14. Repeat step 3-13, but add 20 mL of sodium hydroxide into the flask.
15. Repeat step 3-13, but add 8 mL of iron nitrate solution into the test tube
and add 20 mL of sodium hydroxide into the flask
16. Using a thermometer, measure the temperature of the room.
Observations
Table 1. Physical Properties of Reactants and Products Before and After
Mixing
Before mixing (Reactants)
Physical
Properties
After mixing
(Products)
iron nitrate
sodium
hydroxide
State
liquid
liquid
liquid & solid
Colour
orange-yellow
colourless
orange-brown
Clarity
clear
clear
cloudy
Room
Temperature (oC)
22
22
Table 2. Masses of Reactants and Products Before and After Mixing Different
Volumes of Reactants
Mass (g)
Reactants (and
Products (and
apparatus)
apparatus)
Volume of iron nitrate
solution (mL)
Volume of sodium
hydroxide solution
(mL)
Trial
#
4
10
1
146.5
146.5
4
10
2
166.1
166.1
4
10
3
166.1
166.2
4
4
4
20
20
20
1
3
157.4
174.8
176.8
157.5
174.6
176.8
8
20
1
161.3
161.3
8
20
2
180.9
180.9
8
20
3
180.6
180.6
2
Analysis:
Sample calculation (for 4 mL of iron (III) nitrate and 10 mL of sodium
hydroxide):
mean mass =
=
mass1 +mass2 +mass3
number of masses
146.5𝑔+166.1𝑔+166.1𝑔
3
= 159.6 𝑔
Table 3. Mean masses of reactants and products before and after mixing
Mean Mass (g)
Mean volume of iron
nitrate (mL)
Mean volume of
sodium hydroxide
(mL)
Reactants (and apparatus)
Products (and
apparatus)
4
10
159.6
159.6
4
20
169.7
169.6
8
20
174.3
174.3
See Figure 1 (page 8) for a scatterplot of the mean mass of reactants versus
products.
See Figure 2 (page 9) for a bar graph comparing the mean masses of reactants
and products.
Figure 1. Mean Masses of Reactants vs.
Products for Iron (III) Nitrate Mixed
with Sodium Hydroxide
Mean Mass of Products (g)
176
174
172
170
168
166
164
162
160
158
155
160
165
170
175
Mean Mass of Reactants (g)
180
Figure 2. Mean Masses of Reactants and Products
for Different Starting Volumes of Iron (III) Nitrate
and Sodium Hydroxide
Reactants
200
Products
180
160
Mean Mass (g)
140
120
100
80
60
40
20
0
14
24
28
Total Volume of Reactants (mL)
Questions:
1. After the reaction, the clarity change indicated that a precipitate formed;
furthermore, the formation of the orange-brown solid indicated a colour
change.
2. The mean masses for all three volumes had the products 0.1g less than
the reactants. However, we would consider this difference insignificant
compared to the overall mass of the reactants, especially considering
experimental errors that may occur, such as transfer of water or dirt from
hands to the flask between mass measurements.
3. iron nitrate + sodium hydroxide  iron hydroxide + sodium nitrate
Conclusion:
The mass of the reactants is the same as the mass of the products for chemical
reactions. The small difference between reactants and products (0.1 g) is not
significant compared to the size of the overall mass, as is evident in Figure 2,
where for all volumes the bars appear the same size for reactants and
products. Furthermore, Figure 1 shows an equal increase in product mass for
increased reactant mass.
As is evident from the masses, the atoms of reactants simply rearrange into
product substances, which can be represented by the following balanced
chemical equation:
Fe(NO3)3(aq) + 3 NaOH(aq)  Fe(OH)3(s) + 3 NaNO3(aq)
Hence, the mass is the same before and after the reaction because all the atoms
from the reactants are accounted for in the products.
Evaluation:
There is a watermark on the electronic balance, so the flask may have had
water on it when the mass was measured. If the flask has less water from when
the reactants were measured to when the products were measured, then the
products mass would appear lower than it should be. The flask should be dried
on the outside after being rinsed before performing the next reaction.
This investigation’s method did not include a reaction that produces a gas,
which may create a difference in mass between reactants and products. A
sealable metal container with a screw-top lid should be used for such a
reaction involving, for example, hydrochloric acid and sodium bicarbonate as
reactants.
Reference:
Dickinson, Tom. 2009. ON Science 10. McGraw-Hill Ryerson. Whitby. p160165,172