The Enthalpy Change of a Chemical Reaction, homework help
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The Enthalpy Change of a Chemical Reaction
Experiment 1
1.Record the following for each of the three trials:
·Trial 1
|
a |
Mass of the empty calorimeter (g) 18.6g |
|
b |
Initial temperature of the calorimeter (°C) 21.5°C |
|
c |
Maximum temperature in the calorimeter from the reaction (°C) 35.0°C |
|
d |
Calculate ΔT by subtracting (b) from (c) (°C) ΔT = Tmaximum – Tinitial 35.0°C-21.5°C=13.5°C |
|
e |
Mass of the calorimeter and its contents after the reaction (g) 68.74g |
|
f |
Calculate the mass of the contents of the calorimeter (g) by subtracting (a) from (e) 68.74g-18.6g=50.14g |
|
g |
Calculate the moles of Mg reacted (MW = 24.305 g/mole) ? 50mL of 1M HCI is 50/1000×1=0.05 .15/24.305=.006g/mole |
·Trial 2
|
a |
Mass of the empty calorimeter (g) 18.6g |
|
b |
Initial temperature of the calorimeter (°C) 21.5°C |
|
c |
Maximum temperature in the calorimeter from the reaction (°C) 44.0°C |
|
d |
Calculate ΔT by subtracting (b) from (c) (°C) ΔT = Tmaximum – Tinitial 44.0°C-21.5°C=22.5°C |
|
e |
Mass of the calorimeter and its contents after the reaction (g) 68.83g |
|
f |
Calculate the mass of the contents of the calorimeter (g) by subtracting (a) from (e) 68.83-18.6=50.23 |
|
g |
Calculate the moles of Mg reacted (MW = 24.305 g/mole) .25/24.305=.010g/mole |
·Trial 3
|
a |
Mass of the empty calorimeter (g) 18.6g |
|
b |
Initial temperature of the calorimeter (°C) 21.5°C |
|
c |
Maximum temperature in the calorimeter from the reaction (°C) 52.9°C |
|
d |
Calculate ΔT by subtracting (b) from (c) (°C) ΔT = Tmaximum – Tinitial 52.9°C-21.5°C=31.4°C |
|
e |
Mass of the calorimeter and its contents after the reaction (g) 68.92g |
|
f |
Calculate the mass of the contents of the calorimeter (g) by subtracting (a) from (e) 68.92g-18.6g=50.32 |
|
g |
Calculate the moles of Mg reacted (MW = 24.305 g/mole) .35/24.305=.014g/mole |
2.Calculate the heat released into the solution for the 3 reactions, according to the formula:
|
qreaction= (Ccal * ΔT) + (mcontents* Cpcontents* ΔT) |
3.
Assume Cpcontents= Cpwater= 4.18 J/g °C
|
a |
Trial 1 (J) (4.18J/g°C)(68.74g)(35.0°C-21.5°C)= 3878.9982 J/g°C |
|
b |
Trial 2 (J) (4.18J/g°C)(68.83g)(44.0°C-21.5°C)= 6473.4615 J/g°C |
|
c |
Trial 3 (J) (4.18J/g°C)(68.92g)(52.9°C-21.5°C)= 9045.88784 J/g°C |
4.Find the molar heat of reaction for each experiment in units of kilojoules / (mole of Mg) by dividing the heat of reaction (converted to kJ by dividing by 1000) by the moles of Mg used.
|
a |
Trial 1 (kJ/mol) |
|
b |
Trial 2 (kJ/mol) |
|
c |
Trial 3 (kJ/mol) |
5.Calculate and record the average molar heat of reaction from the three results:
