Deicer Lab
Abstract
Through three different experiments we were to find the quality of NaCl as a deicer. These
experiments included testing the freezing point depression of NaCl in solution at two different
concentrations, testing for the H of an aqueous NaCl solution, and combining NaCl with MgCl2
in an aqueous solution to test for freezing point depression. Through these various experiments
we found NaCl to be the best deicer for our region due to its proficient freezing point
depression
and
its
cost
efficiency.
Introduction
As scientists we were given the task to find the overall effectiveness of NaCl as a deicer. In
choosing the best deicer we are comparing NaCl to KCl, MgCl2, and CaCl2. We believed NaCl to
be the best deicer as it is well know that NaCl is quite commonly used in the United States as a
deicer on roads and sidewalks during the winter. To determine whether or not NaCl is the best
deicer we administered three days of separate experiments. These experiments helped us to
find our deicer’s maximum freezing point depression, its H, and its overall efficiency as a deicer.
The information obtained through these experiments is crucial to public safety during the
winter as the ability to melt ice on roads can be the difference in saving someone’s life. Also, to
have an efficient deicer that is proficient in the conditions needed, and is economically savvy
for whoever is supplying the salt for these roads is essential when testing for deicing quality.
There has been a lot of work done previously to find the most efficient deicer. We have been
using salt to control snow and ice on roadways since 1930. However, we are now looking into
the environmental effects of salts as deicers along with other potentially harmful effects. One
current study is looking into the corrosive effects of salts on our vehicles. Experimental
Our experiments began on day one by filling a 400ml beaker with ice and an arbitrary amount
of rock salt in order for our ice bath to reach sub-zero degree temperatures. We then measured
10ml of deionized water using a 10ml graduated cylinder and combined 0.25g NaCl with the
water in a test tube. The test tube was then submerged in the ice bath. Using logger pro with
the temperature probe the temperature probe was inserted into the aqueous solution and the
freezing point was recorded when ice crystals are detected. We repeated these steps two more
times and repeated them three more times with 0.50g NaCl and 10ml of deionized water.
As we moved on to our day two experiments we were to find the H of solution of NaCl and
deionized water. We did this by constructing a calorimeter using the pink foam provided and a
piece of paper to cover it. A 400ml beaker was filled with deionized water and was heated up
until using a hot plate. We began with a set value of 5ml of room temperature water and
arbitrary amounts of hot water being added into the calorimeter together. Using logger pro
with a temperature probe we were able to find the final temperature of the two combined
liquids in the calorimeter. The calorimeter was covered with a piece of paper and a hole was cut
in the middle in order for the temperature probe to fit in the calorimeter. These steps were
repeated two more times using the other volumes of hot water. We then measured another
10ml of deionized water, recorded the initial temperature using the temperature probe with
logger pro, and mixed 0.50g of NaCl with the water into a test tube. The final temperature of
the
aqueous
solution
was
recorded
and
repeated
two
more
times.
On day 3 we first decided to test the freezing point depression of a supersaturated solution of
NaCl in 10ml deionized water. We attempted this and quickly concluded that this was not
obtainable under lab conditions as the theoretical freezing point of this solution is around -22C.
We then concocted mixture of 0.25g of NaCl and 0.25g MgCl2 in 10ml of deionized water. We
repeated the steps used in day 1 with our new solution and the final temperature were
recorded. These steps were repeated two more times using the same concentrations.
Results
&
Discussion
Day
One
Results
Trial| Volume H2O(ml)| Grams NaCl| Molarity of Solution| Final Freezing temperature(C)|
Theoretical Change in Temperature(C)| 1| 10| 0.255| 0.436| -1.5| -0.45|
2|
10|
0.255|
0.436|
-1.2|
-0.45|
3|
10|
0.250|
0.428|
-1.2|
-0.44|
1|
9.9|
0.502|
0.868|
-3.6|
-0.89|
2|
9.9|
0.499|
0.863|
-3.2|
-0.88|
3|
10|
0.503|
0.861|
-3.3|
-0.88|
Calculations
for
Day
One
Tf=(mass
solute)(i)(molarity
of
solution)
Sample
Calc:
(.512)(2)(.863)=.8837
Molality=mols
solute/kg
of
solution
Sample Calc: 0.499gNaCl/mm NaCl (58.44g)=.00854mol=> .00854mol/.0099kg=.863M Analysis
Day
One
Through our data acquisition on day one our predicted values for the change in temperature of
our NaCl solution in water was slightly off. This was most likely due to recording the freezing
temperature sometime after the precise moment of the solution freezing. However, we
predicted that as we doubled our concentration of NaCl in solution the freezing point
depression would also double which is consistent with our results. Through our day one
experiments we were able to better understand the ability of NaCl as a deicer by understanding
how the freezing point depression changes based on concentration. We could further test these
results
by
testing
with
different
concentrations
of
NaCl.
Day
2
Results
Trial| Volume Room Temperature Water (ml)| Volume Hot Water (ml)| Temperature Initial
Room Temp Water(C)| Temperature Initial Hot Water (C)| Temperature Initial Calorimeter (C) |
Temperature Final Waters Combined| Heat Capacity of Calorimeter| 1| 5| 5.5| 22.3| 100.2|
23.3|
56.3|
9.06|
2|
3|
5|
5|
7.9|
8.1|
22.7|
21.8|
100.1|
99.7|
21.9|
22.6|
64.4|
64.7|
7.24|
6.86|
Trial| Mass NaCl(g)| Volume H2O(ml)| Temperature Initial H2O (C)| Temperature Final Solution
(C)|
1|
0.503|
9.9|
21.9|
21.1|
2|
0.501|
9.9|
22.9|
22.0|
3|
0.502|
10|
22.5|
21.5|
H
5.37|
average
KJ/mol|
Ccal
Average|
7.72|
Calculations
Day
2
Qwater+Qsalt+Qcal=
H
Qwater,
Qsalt
=mc
T
Qcal=Ccalx
T
Analysis
Day
2
We found our H to be positive. However, our H was slightly off of what we predicted but was
still fairly close. We predicted the H to be the key numerical value of how well NaCl will work as
a deicer. However, we found the effectiveness of our deicer to be based on the amount of ions
dissolved in water, not helping NaCl’s case as it only breaks into two ions where as something
like CaCl2 breaks into three. We could improve our results by carrying out the same experiment
with a more efficient calorimeter and not using paper to cover it.
Day
3
Results
Trial| Volume H2O (ml)| Mass NaCl(g)| Mass MgCl2(g)| Mol NaCl| Mol MgCl2| Molality of
Solution| Final Temperature(C)| 1| 10| 0.255| 0.258| .00436| .00271| 0.707| -2.6|
2|
9.9|
0.252|
0.251|
.00431|
.00264|
0.702|
-2.8|
3|
10|
0.253|
0.254|
.00432|
.00267|
0.699|
-3|
Calculations
Day
3
For
Molality,
see
day
one
calculations.
Analysis
Day
3
We began day three by testing the freezing point of a supersaturated solution of NaCl in
deionized water. After waiting twenty minutes we concluded the solution will never freeze
given lab conditions. In order for the solution to freeze, it would need to get to around -22C.
When adding 0.250g of NaCl and 0.250g MgCl2 to 10ml of deionized water we expected the
freezing point depression to be higher than that of just NaCl due to the vant’hoff factor.
However, this was not the case as the average freezing point depression for the two
compounds together was about 2.8C and that of just NaCl was 3.4C. This difference could be
due to human error when pouring the salt into test tubes or when observing the precise time of
freezing for the solution. We could further test our results by testing NaCl with other
compounds
of
other
Vant’hoff
factors.
Conclusion
Through our various experiments we determined NaCl to be the best deicer, especially for our
region. From our day one experiments we were able to conclude that as you double the
concentration of NaCl in solution, the freezing point depression also doubles. Also, the
immensity of the freezing point depression was very high for such little concentrations of NaCl
used. Through day two we determined our H to be around +5.37, which compared with the
theoretical of +3.87, gives us a percent error of 38.75%. The percent error is fairly significant
and was possibly due to loss of heat when transferring liquids as well as using a piece of paper
to cover the calorimeter. Lastly, through our day three experiments we determined that it was
not obtainable to determine the freezing point of a supersaturated solution of NaCl in water
under lab conditions. We looked the value of it up and found a supersaturated solution of NaCl
is able to melt ice all the way down to -22.5C, which makes it ideal for our region as it seldom
gets colder than that in Minnesota. As we proceeded to test a solution of 0.25g of NaCl with
0.25g of MgCl2 in water we found the freezing point depression to be lower than that of just
0.50g NaCl in solution concluding NaCl a better deicer by its ‘self. Also, NaCl is fairly inexpensive
and can be bought for 1-2$ for a Kg when purchased in high quantities. One downfall of the
NaCl as a deicer is the environmental factor. NaCl is Corrosive, damages concrete, and can
destroy vegetation. However, in areas like the city the environmental aspect is not much of a
factor. Even though the environmental factors of NaCl when being used a deicer aren’t too
great, the efficiency of NaCl is so proficient both cost wise and in its overall effectiveness as a
deicer that it outweighs the contradictions of its environmental factors. Therefore, NaCl is the
best deicer. This is important due to the need for salt to deice roads as it is a huge safety risk
without it. Not only do we want the salt to be proficient but to be cost efficient too as pertain
to
the
qualities
of
NaCl
as
a
deicer.
References
"CORROSIVE EFFECTS OF DEICING SALTS ON AUTOMOBILES - Transport Research International
Documentation - TRID." CORROSIVE EFFECTS OF DEICING SALTS ON AUTOMOBILES - Transport
Research International Documentation - TRID. N.p., n.d. Web. 07 Mar. 2013. "Deicing." The
Environmental Literacy Council -. N.p., n.d. Web. 07 Mar. 2013. "Melting Snow & Ice WithÂ
Salt." About.com Chemistry. N.p., n.d. Web. 07 Mar. 2013.