Determination of the Specific Heat of an Unknown Metal and Heat of Reaction by Hesss Law
Introduction to Heat, Specific Heat, & Heat of Reaction:
1) Heat (q) can be defined as the flow of energy into and out of a system due to a temperature difference between the thermodynamic system and its surroundings.
2) Heat energy will flow from the region of higher temperature to the region of lower temperature until thermal equilibrium has been reached.
a. At thermal equilibrium, the temperature of the two regions will be equal at any one time.
3) The formula for heat is as follows: q = s ( m ( ?t
a. q = heat, s = specific heat, m = mass, ?t = change in temperature.
i. Specific heat for water = 4.184 J/g ( oC.
b. Specific heat = the quantity of heat required to raise the temperature of one gram of a substance, one degree Celsius (or Kelvin) at constant pressure.
i. Specific heats are characteristic for that substance at 25oC and constant pressure.
Unknown Metal
Specific Heat (J/(g(oC))
Aluminum
0.901
Iron
0.450
Lead
0.128
Copper
0.387
4) In chemical reactions, heat is often transferred from the system to its surroundings, or vice versa.
a. The substance or mixture of substances under study in which a change occurs is called the thermodynamic system (or just the system.)
b. The surroundings are everything around that thermodynamic system that can interact.
5) The sign of q is very important!
a. If q is positive, heat is absorbed by the system.
i. This process is described as endothermic.
b. If q is negative, heat is released from the system.
i. This process is described as exothermic.
6) The heat of reaction is the value of q required to return a system to the given temperature at the completion of a reaction.
7) The enthalpy of reaction (?Hrxn) is an extensive property of a system that can be used to obtain the heat absorbed/evolved in a reaction at a given temperature and pressure.
a. If at constant pressure, the qp can be determined from the following formula: ?Hrxn = qp.
Introduction to Hesss Law:
1) Hesss law of heat summation states that for a chemical equation that can be written as the sum of two or more steps, the enthalpy change for the overall equation is the sum of the enthalpy changes for the individual steps.
2) Example Calculation:
a. Unknown: 2 CaCO3(s) ( 2 CaO(s) + 2 CO2(g) ?H = ?
b. Known:
i. Ca(s) + C(s) + 3/2 O2(g) ( CaCO3(s) ?Ho1 = 1208 kJ
ii. C(s) + O2(g) ( CO2(g) ?Ho2 = 393.5 kJ
iii. Ca(s) + ½ O2(g) ( CaO(s) ?Ho3 = 635.0 kJ
c. Step 1: Flip Equation #1 (and the sign of ?Ho1)
i. CaCO3(s) (Ca(s) + C(s) + 3/2 O2(g) ?Ho1 = (1208 kJ)
d. Step 2: Cancel Like Terms and Add ?Ho
i. CaCO3(s) ( Ca(s) + C(s) + 3/2 O2(g) ?Ho1 = +1208 kJ
ii. C(s) + O2(g) ( CO2(g) ?Ho2 = 393.5 kJ
iii. Ca(s) + ½ O2(g) ( CaO(s) ?Ho3 = 635.0 kJ
iv. CaCO3(s) ( CaO(s) + CO2(g) ?Horxn = +179.5 kJ
e. Step 3: Multiply by Entire Equation by 2 & ?Horxn
i. 2(CaCO3(s) ( CaO(s) + CO2(g)) ?Horxn = 2(+179.5 kJ)
f. Final Answer:
i. 2 CaCO3(s) ( 2 CaO(s) + 2 CO2(g) ?Horxn = +359 kJ
Substances to include in the Table of Chemical and Physical Properties:
Include the molar mass and safety information for: zinc, zinc oxide, hydrochloric acid.
Determination of the Specific Heat of an Unknown Metal:
1) Place about 400. mL of tap water into a 600 mL beaker and place onto a hotplate.
a. Heat up the water to the boiling point.
2) While waiting for the water to boil, obtain an unknown metal cylinder and determine the mass on an ANALYTICAL balance.
a. Record this mass in the data table attached.
3) Place the metal cylinder into a dry test tube and clamp the tube into the boiling such that the metal cylinder is below surface.
a. The metal should NOT be in direct contact with the water.
4) Obtain the mass of two clean and dried empty Styrofoam cups with the top on an ANALYTICAL balance.
a. These two cups should be stacked on top of one another and the top should have a hole in it to facilitate the use of your thermometer.
b. This set of Styrofoam cups will function as your calorimeter.
5) Add 50.0 mL of deionized water to the calorimeter and obtain the mass on an ANALYTICAL balance.
a. Ensure that no water is clinging to the sides of the Styrofoam cups.
6) Measure the stable temperature of the boiling water to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
a. Record measurement in data table.
b. This temperature is not just that of your water, but of your metal cylinder as well.
7) Measure the stable temperature of the deionized water in the calorimeter to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
a. Record measurement in data table.
8) Remove the clamped test tube and quickly transfer ONLY the heated metal cylinder into the calorimeter.
a. Ensure that you do not transfer any boiling water into the calorimeter.
b. Ensure that you do not allow any of the deionized water from inside the calorimeter to splash out.
9) Replace the top and gently stir the mixture with the thermometer.
10) Record the final temperature in the calorimeter after stabilization to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
11) Following this measurement, remove the metal and thoroughly dry.
12) Repeat this experiment for a second trial.
a. Use 60.0 75.0 mL of deionized water in the calorimeter for this trial.
Procedure for Heat of Reaction by Hesss Law:
1) Obtain the mass of two clean and dried empty Styrofoam cups with the top on an ANALYTICAL balance.
b. These two cups should be stacked on top of one another and the top should have a hole in it to facilitate the use of your thermometer.
c. This set of Styrofoam cups will function as your calorimeter.
2) Measure out 75.0 mL of 6.0 M HCl and carefully transfer into preweighed calorimeter.
a. Be extremely careful when handling the hydrochloric acid solution; it is very caustic.
3) Obtain the mass of the set of cups with the cap on top containing the hydrochloric acid solution.
4) Measure the temperature of the acid solution to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
5) Obtain approximately 0.65g of elemental Zn (preferably the powdered form).
a. Record the mass on an ANALYTICAL balance.
6) Add the metal to the calorimeter, replace the top, and gently stir the mixture with the thermometer.
7) Record the final temperature in the calorimeter after stabilization to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
8) Following this measurement, place the solution in the appropriate waste container and completely dry the set of cups.
9) Repeat this experiment with 75.0 mL of 6.0 M HCl and 1.20 g of zinc oxide.
Clean Up:
1) All water solutions can be disposed of down the sink.
2) All hydrochloric acid solutions should be placed in the appropriate waste container for neutralization.
Sample Data Table for the Specific Heat of an Unknown Metal:
a) Unknown metal cylinder number/letter: ________
b) Mass of unknown metal cylinder in grams:
Trial 1: ________ Trial 2: ________
c) Mass of Styrofoam cups with top in grams:
Trial 1: ________ Trial 2: ________
d) Mass of Styrofoam cups with top plus deionized water in grams:
Trial 1: ________ Trial 2: ________
e) Mass of deionized water in grams (d c):
Trial 1: ________ Trial 2: ________
f) Stable temperature of boiling water/metal cylinder (oC):
Trial 1: ________ Trial 2: ________
g) Stable temperature of boiling water/metal cylinder (K):
Trial 1: ________ Trial 2: ________
h) Stable temperature of water before metal addition (oC):
Trial 1: ________ Trial 2: ________
i) Stable temperature of water before metal addition (K):
Trial 1: ________ Trial 2: ________
j) Stable temperature of water after metal addition (oC):
Trial 1: ________ Trial 2: ________
k) Stable temperature of water after metal addition (K):
Trial 1: ________ Trial 2: ________
l) Amount of heat gained (in Joules) by the deionized water:
Trial 1: ________ Trial 2: ________
m) Amount of heat lost (in Joules) by the metal cylinder:
Trial 1: ________ Trial 2: ________
n) Specific heat of unknown metal (J/g(oC):
Trial 1: ________ Trial 2: ________ Average: ________
o) Identity of unknown metal:
Trial 1: ________ Trial 2: ________
Sample Data Table Heat of Reaction by Hesss Law:
Part 1: Elemental Zinc
a) Balanced equation: ______________________________________
b) Mass of Styrofoam cups with top in grams: _____________
c) Volume of hydrochloric acid solution in milliliters: _____________
d) Mass of Styrofoam cups with top plus HCl solution in grams: ____________
e) Mass of HCl solution in grams (d b): _____________
f) Density of HCl solution in g/mL (e/c): _____________
g) Heat capacity for HCl solution: 3.86 J/g(oC
h) Temperature of HCl solution before metal addition (oC): _____________
i) Temperature of HCl solution before metal addition (K): _____________
j) Mass of zinc (Zn) metal in grams: _____________
k) Moles of zinc (Zn) metal (j/Mm): _____________
l) Temperature of HCl solution after metal addition (oC): _____________
m) Temperature of HCl solution after metal addition (K): _____________
n) Temperature change of HCl solution in oC (l h): _____________
o) Heat (q) of the HCl solution in Joules (g ( (e+j) ( n): _____________
p) Heat (q) of the reaction in Joules (o): _____________
q) Molar heat of reaction for Zn reaction in J/mole (p/k): _____________
r) Molar heat of reaction for Zn reaction in kJ/mole (q/1000): ___________
Part 2: Zinc Oxide
a) Balanced equation: ______________________________________
b) Mass of Styrofoam cups with top in grams: _____________
c) Volume of hydrochloric acid solution in milliliters: _____________
d) Mass of Styrofoam cups with top plus HCl solution in grams: ____________
e) Mass of HCl solution in grams (d b): _____________
f) Density of HCl solution in g/mL (e/c): _____________
g) Specific heat for HCl solution: 3.86 J/g(oC
h) Temperature of HCl solution before oxide addition (oC): _____________
i) Temperature of HCl solution before oxide addition (K): _____________
j) Mass of zinc oxide in grams: _____________
k) Moles of zinc oxide (j/Mm): _____________
l) Temperature of HCl solution after oxide addition (oC): _____________
m) Temperature of HCl solution after oxide addition (K): _____________
n) Temperature change of HCl solution in oC (l h): _____________
o) Heat (q) of the HCl solution in Joules (g ( (e+j) ( n): _____________
p) Heat (q) of the reaction in Joules (o): _____________
q) Molar heat of reaction for zinc oxide reaction in J/mol (p/k): __________
r) Molar heat of reaction for zinc oxide reaction in kJ/mol (q/1000): ______
Part 3: Hesss Law for the Heat of Formation of ZnO:
Unknown Reaction: Zn(s) + ½ O2(g) ( ZnO(s) ?H = ?
a) Balanced equation for elemental zinc: ____________________________
b) Molar heat of reaction for Zn reaction: _____________
c) Balanced equation for zinc oxide: ________________________________
d) Molar heat of reaction for Zn oxide reaction: _____________
e) Balanced equation for synthesis of water: H2(g) + ½ O2(g) ( H2O(l)
f) Molar heat of reaction for synthesis of water: 285.8 kJ/mol
g) Experimental value for heat of formation of ZnO(s): _____________
h) True value for heat of formation of ZnO(s)*: _____________
i) Percent error for heat of formation of ZnO(s): _____________
Barnett & Jones
General Chemistry-I Lab
s = q/(m ( ?t)
(Derived from q = s ( m ( ?t)
PAGE
3
General Chemistry I Lab Barnett
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Lab9-DeterminationoftheSpecificHeatofanUnknownMetalandHeatofReactionbyHesssLawSummer2016-1.doc
Home>Chemistry homework help>lab9
Determination of the Specific Heat of an Unknown Metal and Heat of Reaction by Hesss Law
Introduction to Heat, Specific Heat, & Heat of Reaction:
1) Heat (q) can be defined as the flow of energy into and out of a system due to a temperature difference between the thermodynamic system and its surroundings.
2) Heat energy will flow from the region of higher temperature to the region of lower temperature until thermal equilibrium has been reached.
a. At thermal equilibrium, the temperature of the two regions will be equal at any one time.
3) The formula for heat is as follows: q = s ( m ( ?t
a. q = heat, s = specific heat, m = mass, ?t = change in temperature.
i. Specific heat for water = 4.184 J/g ( oC.
b. Specific heat = the quantity of heat required to raise the temperature of one gram of a substance, one degree Celsius (or Kelvin) at constant pressure.
i. Specific heats are characteristic for that substance at 25oC and constant pressure.
Unknown Metal
Specific Heat (J/(g(oC))
Aluminum
0.901
Iron
0.450
Lead
0.128
Copper
0.387
4) In chemical reactions, heat is often transferred from the system to its surroundings, or vice versa.
a. The substance or mixture of substances under study in which a change occurs is called the thermodynamic system (or just the system.)
b. The surroundings are everything around that thermodynamic system that can interact.
5) The sign of q is very important!
a. If q is positive, heat is absorbed by the system.
i. This process is described as endothermic.
b. If q is negative, heat is released from the system.
i. This process is described as exothermic.
6) The heat of reaction is the value of q required to return a system to the given temperature at the completion of a reaction.
7) The enthalpy of reaction (?Hrxn) is an extensive property of a system that can be used to obtain the heat absorbed/evolved in a reaction at a given temperature and pressure.
a. If at constant pressure, the qp can be determined from the following formula: ?Hrxn = qp.
Introduction to Hesss Law:
1) Hesss law of heat summation states that for a chemical equation that can be written as the sum of two or more steps, the enthalpy change for the overall equation is the sum of the enthalpy changes for the individual steps.
2) Example Calculation:
a. Unknown: 2 CaCO3(s) ( 2 CaO(s) + 2 CO2(g) ?H = ?
b. Known:
i. Ca(s) + C(s) + 3/2 O2(g) ( CaCO3(s) ?Ho1 = 1208 kJ
ii. C(s) + O2(g) ( CO2(g) ?Ho2 = 393.5 kJ
iii. Ca(s) + ½ O2(g) ( CaO(s) ?Ho3 = 635.0 kJ
c. Step 1: Flip Equation #1 (and the sign of ?Ho1)
i. CaCO3(s) (Ca(s) + C(s) + 3/2 O2(g) ?Ho1 = (1208 kJ)
d. Step 2: Cancel Like Terms and Add ?Ho
i. CaCO3(s) ( Ca(s) + C(s) + 3/2 O2(g) ?Ho1 = +1208 kJ
ii. C(s) + O2(g) ( CO2(g) ?Ho2 = 393.5 kJ
iii. Ca(s) + ½ O2(g) ( CaO(s) ?Ho3 = 635.0 kJ
iv. CaCO3(s) ( CaO(s) + CO2(g) ?Horxn = +179.5 kJ
e. Step 3: Multiply by Entire Equation by 2 & ?Horxn
i. 2(CaCO3(s) ( CaO(s) + CO2(g)) ?Horxn = 2(+179.5 kJ)
f. Final Answer:
i. 2 CaCO3(s) ( 2 CaO(s) + 2 CO2(g) ?Horxn = +359 kJ
Substances to include in the Table of Chemical and Physical Properties:
Include the molar mass and safety information for: zinc, zinc oxide, hydrochloric acid.
Determination of the Specific Heat of an Unknown Metal:
1) Place about 400. mL of tap water into a 600 mL beaker and place onto a hotplate.
a. Heat up the water to the boiling point.
2) While waiting for the water to boil, obtain an unknown metal cylinder and determine the mass on an ANALYTICAL balance.
a. Record this mass in the data table attached.
3) Place the metal cylinder into a dry test tube and clamp the tube into the boiling such that the metal cylinder is below surface.
a. The metal should NOT be in direct contact with the water.
4) Obtain the mass of two clean and dried empty Styrofoam cups with the top on an ANALYTICAL balance.
a. These two cups should be stacked on top of one another and the top should have a hole in it to facilitate the use of your thermometer.
b. This set of Styrofoam cups will function as your calorimeter.
5) Add 50.0 mL of deionized water to the calorimeter and obtain the mass on an ANALYTICAL balance.
a. Ensure that no water is clinging to the sides of the Styrofoam cups.
6) Measure the stable temperature of the boiling water to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
a. Record measurement in data table.
b. This temperature is not just that of your water, but of your metal cylinder as well.
7) Measure the stable temperature of the deionized water in the calorimeter to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
a. Record measurement in data table.
8) Remove the clamped test tube and quickly transfer ONLY the heated metal cylinder into the calorimeter.
a. Ensure that you do not transfer any boiling water into the calorimeter.
b. Ensure that you do not allow any of the deionized water from inside the calorimeter to splash out.
9) Replace the top and gently stir the mixture with the thermometer.
10) Record the final temperature in the calorimeter after stabilization to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
11) Following this measurement, remove the metal and thoroughly dry.
12) Repeat this experiment for a second trial.
a. Use 60.0 75.0 mL of deionized water in the calorimeter for this trial.
Procedure for Heat of Reaction by Hesss Law:
1) Obtain the mass of two clean and dried empty Styrofoam cups with the top on an ANALYTICAL balance.
b. These two cups should be stacked on top of one another and the top should have a hole in it to facilitate the use of your thermometer.
c. This set of Styrofoam cups will function as your calorimeter.
2) Measure out 75.0 mL of 6.0 M HCl and carefully transfer into preweighed calorimeter.
a. Be extremely careful when handling the hydrochloric acid solution; it is very caustic.
3) Obtain the mass of the set of cups with the cap on top containing the hydrochloric acid solution.
4) Measure the temperature of the acid solution to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
5) Obtain approximately 0.65g of elemental Zn (preferably the powdered form).
a. Record the mass on an ANALYTICAL balance.
6) Add the metal to the calorimeter, replace the top, and gently stir the mixture with the thermometer.
7) Record the final temperature in the calorimeter after stabilization to the nearest tenth to hundredth of a degree depending on the thermometer calibrations (0.1oC 0.01oC).
8) Following this measurement, place the solution in the appropriate waste container and completely dry the set of cups.
9) Repeat this experiment with 75.0 mL of 6.0 M HCl and 1.20 g of zinc oxide.
Clean Up:
1) All water solutions can be disposed of down the sink.
2) All hydrochloric acid solutions should be placed in the appropriate waste container for neutralization.
Sample Data Table for the Specific Heat of an Unknown Metal:
a) Unknown metal cylinder number/letter: ________
b) Mass of unknown metal cylinder in grams:
Trial 1: ________ Trial 2: ________
c) Mass of Styrofoam cups with top in grams:
Trial 1: ________ Trial 2: ________
d) Mass of Styrofoam cups with top plus deionized water in grams:
Trial 1: ________ Trial 2: ________
e) Mass of deionized water in grams (d c):
Trial 1: ________ Trial 2: ________
f) Stable temperature of boiling water/metal cylinder (oC):
Trial 1: ________ Trial 2: ________
g) Stable temperature of boiling water/metal cylinder (K):
Trial 1: ________ Trial 2: ________
h) Stable temperature of water before metal addition (oC):
Trial 1: ________ Trial 2: ________
i) Stable temperature of water before metal addition (K):
Trial 1: ________ Trial 2: ________
j) Stable temperature of water after metal addition (oC):
Trial 1: ________ Trial 2: ________
k) Stable temperature of water after metal addition (K):
Trial 1: ________ Trial 2: ________
l) Amount of heat gained (in Joules) by the deionized water:
Trial 1: ________ Trial 2: ________
m) Amount of heat lost (in Joules) by the metal cylinder:
Trial 1: ________ Trial 2: ________
n) Specific heat of unknown metal (J/g(oC):
Trial 1: ________ Trial 2: ________ Average: ________
o) Identity of unknown metal:
Trial 1: ________ Trial 2: ________
Sample Data Table Heat of Reaction by Hesss Law:
Part 1: Elemental Zinc
a) Balanced equation: ______________________________________
b) Mass of Styrofoam cups with top in grams: _____________
c) Volume of hydrochloric acid solution in milliliters: _____________
d) Mass of Styrofoam cups with top plus HCl solution in grams: ____________
e) Mass of HCl solution in grams (d b): _____________
f) Density of HCl solution in g/mL (e/c): _____________
g) Heat capacity for HCl solution: 3.86 J/g(oC
h) Temperature of HCl solution before metal addition (oC): _____________
i) Temperature of HCl solution before metal addition (K): _____________
j) Mass of zinc (Zn) metal in grams: _____________
k) Moles of zinc (Zn) metal (j/Mm): _____________
l) Temperature of HCl solution after metal addition (oC): _____________
m) Temperature of HCl solution after metal addition (K): _____________
n) Temperature change of HCl solution in oC (l h): _____________
o) Heat (q) of the HCl solution in Joules (g ( (e+j) ( n): _____________
p) Heat (q) of the reaction in Joules (o): _____________
q) Molar heat of reaction for Zn reaction in J/mole (p/k): _____________
r) Molar heat of reaction for Zn reaction in kJ/mole (q/1000): ___________
Part 2: Zinc Oxide
a) Balanced equation: ______________________________________
b) Mass of Styrofoam cups with top in grams: _____________
c) Volume of hydrochloric acid solution in milliliters: _____________
d) Mass of Styrofoam cups with top plus HCl solution in grams: ____________
e) Mass of HCl solution in grams (d b): _____________
f) Density of HCl solution in g/mL (e/c): _____________
g) Specific heat for HCl solution: 3.86 J/g(oC
h) Temperature of HCl solution before oxide addition (oC): _____________
i) Temperature of HCl solution before oxide addition (K): _____________
j) Mass of zinc oxide in grams: _____________
k) Moles of zinc oxide (j/Mm): _____________
l) Temperature of HCl solution after oxide addition (oC): _____________
m) Temperature of HCl solution after oxide addition (K): _____________
n) Temperature change of HCl solution in oC (l h): _____________
o) Heat (q) of the HCl solution in Joules (g ( (e+j) ( n): _____________
p) Heat (q) of the reaction in Joules (o): _____________
q) Molar heat of reaction for zinc oxide reaction in J/mol (p/k): __________
r) Molar heat of reaction for zinc oxide reaction in kJ/mol (q/1000): ______
Part 3: Hesss Law for the Heat of Formation of ZnO:
Unknown Reaction: Zn(s) + ½ O2(g) ( ZnO(s) ?H = ?
a) Balanced equation for elemental zinc: ____________________________
b) Molar heat of reaction for Zn reaction: _____________
c) Balanced equation for zinc oxide: ________________________________
d) Molar heat of reaction for Zn oxide reaction: _____________
e) Balanced equation for synthesis of water: H2(g) + ½ O2(g) ( H2O(l)
f) Molar heat of reaction for synthesis of water: 285.8 kJ/mol
g) Experimental value for heat of formation of ZnO(s): _____________
h) True value for heat of formation of ZnO(s)*: _____________
i) Percent error for heat of formation of ZnO(s): _____________
Barnett & Jones
General Chemistry-I Lab
s = q/(m ( ?t)
(Derived from q = s ( m ( ?t)
PAGE
3
General Chemistry I Lab Barnett
Applied Sciences
Architecture and Design
Biology
Business & Finance
Chemistry
Computer Science
Geography
Geology
Education
Engineering
English
Environmental science
Spanish
Government
History
Human Resource Management
Information Systems
Law
Literature
Mathematics
Nursing
Physics
Political Science
Psychology
Reading
Science
Social Science
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New Hampshire University
Strayer University
University Of Phoenix
Walden University
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