Using the enthalpies of reaction computed in the lab and the value given for the enthalpy of formation of liquid water, show the Hess's Law determination of the enthalpy of formation of solid magnesium oxide. Show your work. If you are including a scan of your handwritten work, it must be legible.
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
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Room Temperature
Reactant
Trial Number
Mass of reactant (from data)
Moles of reactant (calculate)
Initial time (ti) (from graph)
Initial Temperature (Ti)
(from the graph)
Linear Curve fit slope (m)
(from the graph)
Linear Curve fit intercept (b)
(from the graph)
Final Temperature (T)
(calculate from linear fit data)
AT = T₁-Ti
awater
calorimeter
arxa
AHrxn
26.0°C
Mg(s) + ½ O₂ (g) → MgO (s)
Mg
0.2578 g
1
0.0106 mol
33.5 s
24.3°C
37.23 °C
37.06 °C
12.8 °C
5355.52 J
(5.36 kJ)
128 J
Mg
-5483.52 J
2
0.2551 g
0.0105 mol
41.05 s
29.055 °C
41.72 °C
41.46 °C
12.41 °C
5192.344 J
(5.192 kJ)
-0.005191 °C/s -0.006452 °C/s -0.003932 °C/s -0.003809 °C/s
124.1 J
MgO
-5316.4 J
3
0.4939 g
0.0123 mol
46.52 s
29.791 °C
33.51 °C
33.33 C
3.54 °C
1481.136 J
(1.48 kJ)
35.4 J
-1516.5 J
Use the following to determine the enthalpy of formation of magnesium oxide:
Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)
MgO (s) + 2HCl (aq) → MgCl₂ (aq)+ H₂O (1)
H₂(g) + ½O2 (g) → H₂O (1)
0.5033 g
MgO
0.0125 mol
32.47 s
31.5714 °C
35.27 °C
35.15 °C
3.59 °C
1502.056 J
(1.50 kJ)
35.9 J
-1538.0 J
-517.3 kJ/mol -506.3 kJ/mol -123.3 kJ/mol -123.0 kJ/mol
AH = (calculated in the experiment)
AH = (calculated in the experiment)
AH=285.8 kJ/mol
AH = (determine using Hess's Law)](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F15544970-1f2f-481d-bf68-5c90fa85fc68%2F3b315c63-c9ed-487f-a1b6-431cd6501a58%2Frhz10f_processed.png&w=3840&q=75)
![Calculations:
1. Using the enthalpies of reaction computed in the lab and the value given for the enthalpy of formation of
liquid water, show the Hess's Law determination of the enthalpy of formation of solid magnesium oxide.
Show your work. If you are including a scan of your handwritten work, it must be legible.
2. Compare the value you calculated with the actual value (-601.8 kJ/mol). Show your determination of
percent error. Use the standard equation for this: |
%error
|actual value — experimental value|
|actual value|
x 100%](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F15544970-1f2f-481d-bf68-5c90fa85fc68%2F3b315c63-c9ed-487f-a1b6-431cd6501a58%2F7mhrfjb_processed.png&w=3840&q=75)
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