Calorime try Franz Laurence L. Alvarez Louise Gabrielle M. Valdez
CalorimetryFranz Laurence L. Alvarez
Louise Gabrielle M. Valdez
Theoretical Framework Calorimetry
Science of measuring the heats of reaction Calorimetric techniques: based on the
measurement of heat that may be: Generated (exothermic) Consumed (endothermic) Dissipated
In measuring change in enthalpy (∆H): Construct a “surroundings” retains heat, where
temperature change is observed
Theoretical Framework Calorimeter
Apparatus used to measure heat released or absorbed
Acts as the “surroundings” Changes temperature when heat is transferred to
or from the system
Calorimeter:
Theoretical Framework Heat capacity
Quantity of heat required to change an object’s temperature by 1K
Specific heat capacity Quantity of heat required to change the
temperature of 1 gram of a substance by 1K
Theoretical Framework The heat released (Q) by a reaction is
absorbed by the calorimeter and any substances in the calorimeter.
The following energy balance exists if the only substance in the calorimeter is water:
0 = Qcal + Qwater
Remember: First law of Thermodynamics when energy is transferred from one object to another, it appears as work and/or as heat
Experimental Part A: Calorimeter Constant
This is the final /equilibrium temperature.
This is the initial temperature of calorimeter and water.
10mL of tap water
Calorimeter with
thermometer
Record temperature
until 3 identical readings
50mL of tap water
Heat to 50oC (use
another
thermometer)
10mL of hot water
Calorimeter with tap water
Record temperature every
3s until temp becomes constant for 4 successive
readings.
Part B: Heat of Fusion
This is the final /equilibrium temperature.
Determine weight of beaker with tissue and weight of ice.
This is the initial temperature of calorimeter and water.
10mL of tap water
Calorimeter with
thermometer
Record temperature
until 3 identical readings
Weigh 10g of ice in beaker with tissue paper at bottom
Calorimeter with tap water
Record temperature every 3s until temp becomes constant for 4 successive
readings.
Part C: Heat of Reaction
Place in water bath if temp is not equal
Record temperature of each reagent
Read temperature (initial temp) Measure
volume
Mix reagents in calorimeter
Record temperature every 3s until temp becomes constant
Set I:5.5mL 6M HCl + 4.5mL 6M NaOH
Set II5.5mL 6M HOAc + 4.5mL 6M NaOH
Set III5.5mL 6M HCl + 4.5mL 6M NH4OH
Results Part A
Mass of tap water: 10g Mass of hot water: 10g Initial temperature of tap water: 35oC Initial temperature of hot water: 50oC Equilibrium temperature: 41oC Calorimeter constant, cal/oC: 5 cal/oC
Time (s) 0 3 6 9 12 15Temperature (oC) 40 41 41 41 41 41
Part A.Evaluation of Calorimeter Constant
39.8
40
40.2
40.4
40.6
40.8
41
41.2
0 2 4 6 8 10 12 14 16
Time (s)
Tem
per
atu
re (
C)
Results Part B
Mass of tap water: 10g Mass of ice + beaker +
tissue: 34.45g Mass of beaker + tissue:
24.39g Mass of ice: 10.06g Initial temperature of tap
water: 34oC Initial temperature of ice: 0oC Equilibrium temperature: 7oC Calorimeter constant: 5
cal/oC Heat of fusion of ice, cal/g:
37.74 cal/g
Time (s) Temp (oC)
0 23
3 20
6 17
9 15
12 13
15 12
18 11
21 10
24 10
27 9
30 9
Time (s) Temp (oC)
33 8.5
39 8
42 8
45 7.5
48 7.5
51 7
54 7
55 7
57 7
Part B.Evaluation of Heat Fusion of Ice
0
5
10
15
20
25
0 10 20 30 40 50 60
Time (s)
Tem
per
atu
re (
C)
Results Part C.
Set I: 5.5mL 6M HCl + 4.5mL 6M NaOH
Mols of HCl: 0.033 mols
Mols of NaOH: 0.027 mols
Mols of limiting reagent: 0.027 mols
∆H of neutralization: -15.56 x 103 cal/mol
Time (s) Temperature (oC)
0 35
3 45
6 54
9 58
12 60
15 62
18 63
21 63
24 63
27 63
Part C: Set I
Evaluation of Heat of Reaction of Set I
0
10
20
30
40
50
60
70
0 5 10 15 20 25 30
Time (s)
Tem
per
atu
re (
C)
Part C. Set II: 5.5mL 6M HOAc
+ 4.5mL 6M NaOH
Mols of HOAc: 0.033 mols
Mols of NaOH: 0.027 mols
Mols of limiting reagent: 0.027 mols
∆H of neutralization: -3.61 x 103 cal/mol
Time (s) Temperature (oC)
0 50
3 55
6 56
9 56.5
12 56.5
15 56.5
Part C: Set II
Evaluation of Heat of Reaction of Set II
49
50
51
52
53
54
55
56
57
0 2 4 6 8 10 12 14 16
Time (s)
Tem
per
atu
re (
C)
Part C. Set III: 5.5mL 6M HCl +
4.5mL 6M NH4OH
Mols of HCl: 0.033 mols
Mols of NH4OH: 0.027 mols
Mols of limiting reagent: 0.027 mols
∆H of neutralization: -13.33 x 103 cal/mol
Time (s) Temperature (oC)
0 34
3 43
6 49
9 52
12 55
15 56
18 57
21 57.5
24 58
27 58
30 58
Evaluation of Heat of Reaction of Set III
0
10
20
30
40
50
60
70
0 5 10 15 20 25 30 35
Time (s)
Tem
per
atu
re (
C)
Discussion Part A: Calorimeter Constant Qhot water + Qtap water + Qcalorimeter = 0 *Q = m c ∆ t ; Qcalorimeter = ccalorimeter ∆ t Qcal = -mtapc∆ttap – mhotc∆thot
Part A: Calculations
Qcal = -mtapc∆ttap – mhotc∆thot
= -(10g) (1.00 cal/goC) [(41-35) + (41-50)]oC
= 30 cal
Ccal = Qcal/∆t = 30cal / (41-35)oC = 5 cal/oC
Discussion
Part B: Heat of Fusion
∆Hfusion = (-Qice – Qtap – Qcal) ÷ mice
Part B: Calculations
∆Hfusion = -Qice – Qtap – Qcal ÷ mice
= {[-10.06g(4.184J/goC)(7-0)oC] – [10g(4.184J/goC)(7-34)oC] –
[(5cal/oC)(7-34)oC(4.184J/cal)]} ÷ 10.06g
= 139.15 J/g 33.25 cal/g
Discussion Part C: Heat of Neutralization
∆Hneut = (-Qcal – Qsol’n) ÷ mollimiting
∆ Hneut = (-Ccal∆t – msol’ncsp∆t) ÷ mollimiting
∆ Hneut = [-msol’ncsp(tf - ti) – Ccal (tf - ti)] ÷ mollimiting
Part C: Set I: Calculations
∆Hneut = (-Qcal – Qsol’n) ÷ mollimiting
∆ Hneut = (-Ccal∆t – msol’ncsp∆t) ÷ mollimiting
∆ Hneut = [-msol’ncsp(tf - ti) – Ccal (tf - ti)] ÷ mollimiting
= [(-10g)(1.00cal/goC)(63-35)oC –
(5cal/ oC)(63-35)oC] ÷ 0.027 mol= -15.56 x 103 cal/mol
Part C: Set II: Calculations
∆Hneut = (-10g)(1.00cal/goC)(56.5-50)oC –
(5cal/oC)(56.5-50)oC ÷ 0.027 mol
= -3.61 x 103 cal/mol
Part C: Set III: Calculations
∆Hneut = (-10g)(1.00cal/goC)(58-34)oC –
(5cal/oC)(58-34)oC ÷ 0.027 mol
= -13.33 x 103 cal/mol
COMPARISON OF VALUES
Experimental Values
∆Hfusion = 139.15 J/g ∆Hneut(SET I) = -15.56 x
103 cal/mol ∆Hneut(SET II) = -3.61 x
103 cal/mol ∆Hneut(SET III) = -13.33 x
103 cal/mol
Theoretical Values 333.55 J/g -13.48 x 103 cal/mol
-13.42 x 103 cal/mol
-11.92 x 103 cal/mol
Conclusion and Recommendation Calorimetry is very helpful in determining
heats of reaction especially in chemistry experiments. We found out that heat is related with temperature and it can be defined in many ways.
Conservation of energy is also a part of heat processes were heat is neither created or destroyed but instead, it is passed on by the system to the surroundings or vice versa. Conservation of such energy gives definition for endothermic and exothermic reactions.
Conclusion and Recommendation Calorimeter constant is the specific heat of
the calorimeter. Specific heats of different calorimeters vary from each other.
The heat of fusion is the amount of thermal energy which must be absorbed or evolved for 1 mole of a substance to change states from a solid to a liquid or vice versa. The heat of fusion in the experiment may be positive or negative with respect to different substances. It is endothermic in the experiment with respect to ice.
Conclusion and Recommendation The heat of neutralization is the
amount of heat involved (either given off or absorbed) in the neutralization reaction of acids and bases to form salt and water.
Different factors affect the experiment that led to different experimental errors and that not all experimental measurements were so accurate.