Answer & Explanation:write a conclusion of this documentit is enthalpy of combustion write 150-200 words and try to let it as simple as possible
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enthalpy of combustion
Objectives:
The objectives of this experiment are to gain a better understanding of enthalpy of
combustion, make connections between the number of carbons and the combustibility,
and find a linear relationship between different alcohols and number of present
carbons.
Background:
Living in a generation that is exorbitantly focused on health makes it inevitable to have
heard about “calories” before. However, it is important to note that the differences
between the 150 “calories” in a Twinkie and 150 calories in a science lab are huge. The
“calories” in a twinkie are actually Calories, or kilocalories, and are comprised of 1,000
scientific calories. A calorie in science is the amount of energy it takes to raise the
temperature of water by 1 degrees celsius. Using a few ordinary tools found in the lab,
an experiment can be set up to test the amount of energy required to raise the
temperature of water by a set number of degrees.
Materials:
-Digital thermometer
-Calorimeter
-Spirit lamp
-Methanol
-Ethanol
-Proponal
-Butanol
-Pentanol
Safety:
Methanol:
32.04g/mol
II- Acutely toxic if touched, consumed or inhaled.
VII- Fire and Explosion Hazard, ensure proper extinguishing gear is accessible
VIII- Safety glasses, gloves, and lab gear required.
Ethanol:
46.07 g/mol
II- irritant, flammable, and toxic
VII- Fire and Explosion Hazard, ensure proper extinguishing gear is accessible
VIII- Safety glasses, gloves, and lab gear required.
Proponal:
60.09g/mol
II- Irritant to skin, eyes, and respiratory system
VII- Fire and Explosion Hazard, ensure proper extinguishing gear is accessible
VIII- Safety glasses, gloves, and lab gear required.
Butanol:
74.12 g/mol
II- flammable, irritant, corrosive
VII- Fire and Explosion Hazard, ensure proper extinguishing gear is accessible
VIII- Safety glasses, gloves, and lab gear required.
Pentanol:
88.15 g/mol
II- flammable, irritant, do not inhale
VII- Fire and Explosion Hazard, ensure proper extinguishing gear is accessible
VIII- Safety glasses, gloves, and lab gear required.
Methods:
Set up your spirit lamp ensuring that there is 1.5 centimeters between base and
calorimeter. Use 30 mL of alcohol in your spirit lamp for each test. Measure the initial
weights of both the alcohols and the 150mL of water. Fill your calorimeter with 150 mL
of water. One everything is set up, burn the spirit lamp for five minutes with your first
alcohol inside of it to ensure that the wick is free of any previous substances. When the
five minutes are up, move your spirit lamp under the calorimeter. Place the thermometer
in the calorimeter. Agitating the water every ten seconds, watch the temperature of the
water until it has increased by 20 degrees celsius. After the temperature as increased
by 20 degrees, remove the spirit lamp from beneath the calorimeter, put out the flame,
and reweigh the remaining alcohol, being sure to record the final weight. Repeat this
two more times with the first alcohol, and then repeat the entire process with the
remaining alcohols.
Results
Methanol (32.04 g/mol)
Trials
Alcohol
Initial
Weight
Alcohol
Final
Weight
Consumed
Alcohol Weight
Water Initial
temperature
Water Final
temperature
1
21.84 g
14.31 g
7.53 g
20.8 °C
40.8 °C
2
14.31 g
6.36 g
7.95 g
21.2 °C
41.2 °C
3
22.93 g
14.83 g
8.1 g
21.4 °C
41.4 °C
Average
19.69 g
11.83 g
7.86 g
21.13 °C
41.13 °C
Theoretical ΔcH of methanol = 726.1 kJ/mol
o
Formula used to calculate the experimental enthalpy of combustion:
ΔcH = (mcΔT)/moles of alcohol
= (150g * 4.186J/(g*C)*20C) / (7.86g / 32.04 g/mol)
o
= 12558 J / 0.25 mol
= 51.19 kJ/mol
Ethanol (46.07 g/mol)
Trials
Alcohol
Initial
Weight
Alcohol
Final
Weight
Consumed
Alcohol Weight
Water Initial
temperature
Water Final
temperature
1
31.57 g
24.6 g
6.97 g
21.1 °C
41.1 °C
2
24.6 g
18.9 g
5.7 g
22.5 °C
42.5 °C
3
18.9 g
13.4 g
5.5 g
21.7 °C
41.7 °C
Average
25.02 g
18.97 g
6.05 g
21.77 °C
41.75 °C
Theoretical ΔcH of ethanol = 1366.8 kJ/mol
o
Formula used to calculate the experimental enthalpy of combustion:
ΔcH = (mcΔT)/moles of alcohol
= (150g * 4.186J/(g*C)*20C) / (6.05g / 46.07 g/mol)
= 12558 J / 0.13 mol
= 95.63 kJ/mol
o
Butanol (74.12 g/mol)
Trials
Alcohol
Initial
Weight
Alcohol
Final
Weight
Consumed
Alcohol Weight
Water Initial
temperature
Water Final
temperature
1
24.27 g
19.47 g
4.8 g
23.9 °C
43.9 °C
2
19.47 g
14.35 g
5.12 g
22.6 °C
42.6 °C
3
23.91 g
18.95 g
4.96 g
22.8 °C
42.8 °C
Average
22.40 g
17.59 g
4.96 g
23.1 °C
43.1 °C
Theoretical ΔcH of butanol = 2676 kJ/mol
o
Formula used to calculate the experimental enthalpy of combustion:
ΔcH = (mcΔT)/moles of alcohol
= (150g * 4.186J/(g*C)*20C) / (4.96 /74.12 g/mol)
= 12558 J / 0.067mol
= 187.66 kJ/mol
o
Pentanol (88.15 g/mol)
Trials
Alcohol
Initial
Weight
Alcohol
Final
Weight
Consumed
Alcohol Weight
Water Initial
temperature
Water Final
temperature
1
24.91 g
20.13 g
4.78 g
24.2 °C
44.2 °C
2

3

Average
24.91 g
20.13 g
4.78 g
24.2 °C
44.2 °C
Theoretical ΔcH of pentanol = 3330.63 kJ/mol
o
Formula used to calculate the experimental enthalpy of combustion:
ΔcH = (mcΔT)/moles of alcohol
= (150g * 4.186J/(g*C)*20C) / (4.78g /88.15 g/mol)
= 12558 J / 0.054 mol
= 231.59 kJ/mol
o
R^2 Value of Experimental line = 0.99993
R^2 Value of Theoretical line = 0.99998
Discussion
The values calculated in the results show that the experimental values vary greatly from
the theoretical values. This was expected. The heat generated by the combustion
appears to be lower in the experimental values, but this is likely not the case.What is
most likely happening is that the heat is being lost to the environment, or absorbed by
the instruments used, such as the calorimeter and stand.
The graph also indicates a difference in the slopes of the theoretical and experimental
lines. This is not seen as an error, as the example graph provided to us had this factor.
It is possible that the alcohols used lose more heat to the environment if they have a
higher ΔcH as the heat cannot be absorbed fast enough. But this is just a hypothesis
and remains to be verified.
o
As shown by our r^2 values, our data within the experimental line is very consistent, but
there are some sources of error outside of that. The loss of some of the heat produced
and the differences between the experimental and theoretical values, for example,
indicate a source of error. To achieve results closer to those pictured by the theoretical
values, the experiment should be redone in a closed system to avoid loss of energy. It is
very unlikely, however, that perfect values can be replicated in our laboratory setting.
Other changes that we would perform if the experiment was redone are: reduction of
water to speed up the process and the addition of an automatic stirrer to avoid errors
that may happen due to inconsistent stirring.

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