|
|
|
Hot Pack Cold Pack.docx
Hot_Pack_Cold_Pack.docx
Showing 4-5 out of 5
Hot Pack Cold Pack.docx-Hot Pack/Cold Pack Intro :...
Hot_Pack_Cold_Pack.docx-Hot Pack/Cold Pack Intro : Hot
Hot Pack Cold Pack.docx-Hot Pack/Co...
Hot_Pack_Cold_Pack.docx-Hot Pack/Cold Pack Intro : Hot
Page 4
Table 4: Mass and Cost of Salts Used in 500 mL Cold and Hot Pack
MgSO
4
CaCl
2
LiCl
LiBr
KNO
3
NH
4
NO
3
KCl
NaC
2
H
3
O
2
q
water
(kJ)
102.5
102.5
102.5
102.5
-48.1
-48.1
-48.1
102.5
q
salt
(kJ)
-102.5
-102.5
-102.5
-102.5
48.1
48.1
48.1
-102.5
Moles
salt
1.33
6.03
3.20
2.36
1.57
2.10
3.40
7.43
Mass
salt
(g)
160
669
136
205
159
168
253
609
Total
Cost ($)
16.00
46.83
17.68
26.65
11.13
8.40
15.18
42.63
Using
q
water
for both the hot and cold experiments, the mass of salt that is necessary to change the
temperature of the water to the target point can found be found as well as the total price of salt. A
sample calculaon using CaCl
2
is given as follows:
q
water
=−
q
CaC l
2
,q
CaC l
2
=−
102.5
kJ
∆H
soln
=
q
CaC l
2
n
,
−
17
kJ
mol
=
−
102.5
kJ
n
,n
=
6.03
mol
m
CaC l
2
=
n × MW , m
CaC l
2
=
6.03
mol ×
110.98
g
mol
,m
CaC l
2
=
669
g
(
5)
TotalCost
=
m
CaC l
2
×
Cost
m
CaC l
2
,Total Cost
=
669
g×
$
0.07
g
,TotalCost
=
$
46.83
(
6
)
Discussion
:
The purpose of this experiment was to design a hot and cold pack using the dissoluon process
that common salts undergo in water. In choosing the salt that would provide for the best opon in
creang a commercially viable hot pack, magnesium sulfate appears to be the best opon because it is
not at all toxic as indicated by its unavailable LD
50
, is the cheapest “hot” salt, and provides the second
lowest mass to reach the target temperature when dissolved in 500 mL of water. The salt that appears
to offer the most commercially viable cold pack is potassium nitrate. Potassium nitrate is desirable due
to its comparavely low toxicity, low cost, and in providing the least amount of mass to aain the target
temperature of all “cold” salts in 500 mL of water. If these salts were to actually be used in a hot or cold
pack, the magnesium sulfate hot pack would only need to be labeled with precauonary advice
acknowledging the possibility of skin or eye irritaon. The potassium nitrate cold pack would need to be
Page 5
labeled with precauonary advice indicang that ingesng large amounts of potassium nitrate can be
harmful as well as the risk of explosion that is presented by igning or extensively heang the salt.
Although seemingly minimal, there are a few significant sources of error provided in this
experiment. The most prevalent source of error is the imperfect nature of the calorimeter. Since it is
impossible to contain all heat within the Styrofoam cup, the final temperature readings are lower than
expected for the “hot” salts and more than expected for the “cold” salts. Even though the technique of
extrapolaon was applied to the temperature graphs in aempt to make up for the amount of heat
gained from and lost to the surroundings, the temperature values are sll not exact and erroneous.
Error is also included in the actual mass of salt that was placed in soluon with the water because some
salt remained on the watch glass aſter the rest was inside the coffee cup. This is an issue because the
mass of the salt was measured prior to being placed in soluon. Aempts to overcome these sources of
error include using a more insulated calorimeter that would prevent the exchange of heat from the
system and surroundings, as well as applying a more precise method of introducing the salt into
soluon.
Aſter doing research about real world cold and hot packs and how they are made in industry, it
became apparent that magnesium sulfate and potassium nitrate were not the only commercially viable
salts used in hot and cold packs that were tested in this experiment. In reality, the use of calcium
chloride salt is also used in hot packs and as an ice melt ingredient. The other viable “cold” salt that is
widely used -maybe the most prevalent in the industry- is ammonium nitrate. Although the health
effects of this salt are widely recognized, it is sll a popular and effecve salt to use in instant cold packs.
Since the only consideraons that were taken into account in judging a hot/cold pack were the
temperature change of the water as an indicator of effecveness, toxicity, and cost, other possible
scenarios exist that may limit the usefulness of a parcular salt. These scenarios include the effects a salt
has on the environment over long periods of me, possible changes to the specific heat of the heated or
cooled soluon that limits the length of use, and the reacvity a salt has.
Ace your assessments! Get Better Grades
Browse thousands of Study Materials & Solutions from your Favorite Schools
Indiana University-Bloomi...
Indiana_University-Bloomington
School:
Principles_of_Chemistry_and_Biochemistry
Course:
Great resource for chem class. Had all the past labs and assignments
Leland P.
Santa Clara University
Introducing Study Plan
Using AI Tools to Help you understand and remember your course concepts better and faster than any other resource.
Find the best videos to learn every concept in that course from Youtube and Tiktok without searching.
Save All Relavent Videos & Materials and access anytime and anywhere
Prepare Smart and Guarantee better grades
Know more
Students also viewed documents
lab 18.docx
lab_18.docx
Course
Course
3
Module5QuizSTA2023.d...
Module5QuizSTA2023.docx.docx
Course
Course
10
Week 7 Test Math302....
Week_7_Test_Math302.docx.docx
Course
Course
30
Chapter 1 Assigment ...
Chapter_1_Assigment_Questions.docx.docx
Course
Course
5
Week 4 tests.docx.do...
Week_4_tests.docx.docx
Course
Course
23
Week 6 tests.docx.do...
Week_6_tests.docx.docx
Course
Course
106
