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7/28/2019 CHEM WB Ch.37
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Experiment 37.1
SolutionP. 1 / 37
Experiment 37.1
Determining the standard
enthalpy change of formationof a metal carbonate
Experiment Video
http://localhost/var/www/apps/conversion/tmp/scratch_6/exp37_1e.mpghttp://localhost/var/www/apps/conversion/tmp/scratch_6/exp37_1e.mpghttp://localhost/var/www/apps/conversion/tmp/scratch_6/exp37_1e.mpghttp://localhost/var/www/apps/conversion/tmp/scratch_6/exp37_1e.mpg7/28/2019 CHEM WB Ch.37
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Experiment 37.1
SolutionP. 2 / 37
Objective
To determine the standard enthalpy change of formation of
calcium carbonate.
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Experiment 37.1
SolutionP. 3 / 37
Apparatus and Chemicals
Each group will need:
Safety spectacles Electronic balance
Thermometer (with a reinforced bulb) (10C to
110C)
Beaker (250 cm3) Forceps
Spatula
Expanded polystyrene cup Polystyrene lid with a hole
Weighing bottle (Cont)
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Experiment 37.1
SolutionP. 4 / 37
Apparatus and Chemicals
Measuring cylinder (100 cm3)
Hydrochloric acid (1.0 M, 200 cm3
) Calcium granules (1 g)
Calcium carbonate granules or powder (3 g)
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Experiment 37.1
SolutionP. 5 / 37
Safety precautions
1. Do not touch calcium with bare hands. It may cause
burns.
2. Use calcium granules, but not calcium powder,
otherwise the reaction would be too vigorous.
3. Handle acid with care. In case any acid gets into your
eyes, report to your teacher immediately, and flush your
eyes under running water for at least 3 minutes. If any
acid gets onto your skin, wash the affected area with
plenty of water.
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Experiment 37.1
SolutionP. 6 / 37
Safety precautions
Calcium granules
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Experiment 37.1
SolutionP. 7 / 37
Procedure
A. Reaction of calcium with dilute hydrochloric acid
Determining the standard
enthalpy change of formationof a metal carbonate
7/28/2019 CHEM WB Ch.37
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Experiment 37.1
SolutionP. 8 / 37
Procedure
1. (a) Weigh out
approximately 1 g of
calcium granules in a
weighing bottle,M1.
(b) Record the mass in
Table 37.1.
Note
Remember to press theTare button of the
electronic balance to set
the reading to zero
before use.
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Experiment 37.1
SolutionP. 9 / 37
Procedure
2. (a) Using a measuring
cylinder, measure
100 cm3 of 1.0 M
hydrochloric acid
(Figure 37.1a).
Figure 37.1a
measuring
cylinder
100 cm3 of 1.0 M
hydrochloric acid
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Experiment 37.1
SolutionP. 10 / 37
(b) Pour the acid into an expanded polystyrene cup
(Figure 37.1b).
Procedure
Figure 37.1b
measuring cylinder
100 cm3 of 1.0 M
hydrochloric acid
expanded
polystyrene
cup
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Experiment 37.1
SolutionP. 11 / 37
Procedure
(c) Put the cup into a beaker (Figure 37.1c).
(d) Record the temperature of the acid, T1, in Table
37.1.
Figure 37.1c
thermometer
1.0 M hydrochloric acid
beaker
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Experiment 37.1
SolutionP. 12 / 37
Procedure
3. (a) Quickly add the weighed
calcium granules to the
acid.
(b) Quickly cover the cup with
a lid.
CautionDo not touchcalcium with bare
hands. It may cause
burns.
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Experiment 37.1
SolutionP. 13 / 37
Procedure
(c) Insert a thermometer into the solution through the
hole in the lid (Figure 37.2).
1.0 M hydrochloric
acid
Figure 37.2
beaker
lid
thermometer
calcium granules
expanded
polystyrene
cup
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Experiment 37.1
SolutionP. 14 / 37
Procedure
4. (a) Re-weigh the weighing bottle with calcium
granules residue,M2.
(d) Stir the contents gently.
(e) Record the maximum temperature reached by thesolution, T
2, in Table 37.1.
(b) Record the mass in Table 37.1.
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Experiment 37.1
SolutionP. 15 / 37
Total mass of weighing bottle and calcium
granules before addition,M1
(g)
Total mass of weighing bottle and calcium
granules residue after addition,M2
(g)
Mass of calcium granules added for reaction,
M1M2 (g)
Initial temperature of the solution, T1(C)
Final temperature of the solution, T2
(C)
Temperature change, T2T1 (C)
Procedure
Table 37.1
4.05
3.06
0.9926.2
50.7
+24.5
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Experiment 37.1
SolutionP. 16 / 37
Procedure
B. Reaction of calcium carbonate with dilute
hydrochloric acid
Determining the standard
enthalpy change of formation
of a metal carbonate
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Experiment 37.1
SolutionP. 17 / 37
Procedure
5. (a) Weigh out
approximately 3 g of
calcium carbonate in a
weighing bottle,M3.
(b) Record the mass in
Table 37.2.
Note
Remember to press theTare button of the
electronic balance to set
the reading to zero
before use.
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Experiment 37.1
SolutionP. 18 / 37
Procedure
6. (a) Using a measuring
cylinder, measure
100 cm3 of 1.0 M
hydrochloric acid
(Figure 37.3a).
Figure 37.3a
measuring
cylinder
100 cm3 of 1.0 M
hydrochloric acid
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Experiment 37.1
SolutionP. 19 / 37
(b) Pour the acid into an expanded polystyrene cup
(Figure 37.3b).
Procedure
Figure 37.3b
measuring cylinder
1.0 M
hydrochloric acid
expanded
polystyrene
cup
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Experiment 37.1
SolutionP. 20 / 37
Procedure
(c) Put the cup into a beaker (Figure 37.3c).
(d) Record the temperature of the acid, T3, in Table
37.2.
Figure 37.3c
thermometer
1.0 M hydrochloric acidbeaker
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Experiment 37.1
SolutionP. 21 / 37
Procedure
7. (a) Quickly add the weighed calcium carbonate to the
acid.(b) Quickly cover the cup with a lid.
(c) Insert a thermometer into the solution through the
hole in the lid (Figure 37.4).
Figure 37.4beaker
1.0 M hydrochloric acid
lid
thermometer
calcium carbonate
expanded
polystyrene
cup
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Experiment 37.1
SolutionP. 22 / 37
Procedure
8. (a) Re-weigh the weighing bottle with calcium
carbonate residue,M
4.
(d) Stir the contents gently.
(e) Record the maximum temperature reached by thesolution, T
4, in Table 37.2.
(b) Record the mass in Table 37.2.
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Experiment 37.1
SolutionP. 23 / 37
Total mass of weighing bottle and calcium
carbonate before addition,M3
(g)
Total mass of weighing bottle and calcium
carbonate residue after addition,M4
(g)
Mass of calcium carbonate added for
reaction,M3M4 (g)
Initial temperature of the solution, T3
(C)
Final temperature of the solution, T4
(C)
Temperature change, T4T3 (C)
Procedure
Table 37.2
6.07
3.05
3.0226.2
28.5
+2.3
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Experiment 37.1
SolutionP. 24 / 37
Calculations
9. (a) Write a chemical equation (Equation 1) for the
reaction between calcium and dilute hydrochloric
acid.
Ca(s) + 2HCl(aq) CaCl2(aq) + H2(g)
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Experiment 37.1
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(b) Calculate the heat
evolved when
calcium used in partA reacts completely
with dilute
hydrochloric acid.
Calculations
Note
Assume that the specific heat
capacity and density of the
solution are the same as those
of water i.e. 4.2 J g1 K1 and
1.0 g cm3
respectively.
Heat evolved = m cT
=
=
100 cm3 1.0 g cm3 4.2 J g1 K1 24.5 K
10290 J
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Experiment 37.1
SolutionP. 26 / 37
Calculations
(c) Hence, calculate the heat evolved when 1 mole of
calcium reacts completely with dilute hydrochloric
acid.
Number of moles of calcium used =
From the equation, the mole ratio of Ca : HCl
=
= 0.0247 mol
1 : 2
0.99 g
40.1 g mol1
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Experiment 37.1
SolutionP. 27 / 37
Calculations
Number of moles of dilute hydrochloric acid used
Heat evolved when 1 mole of calcium reactscompletely with dilute hydrochloric acid
=
=
is in excess.
=
=
0.1 mol
HCl
=
416599 J mol1
416.6 kJ mol1
10290 J
0.0247 mol
1.0 mol dm3
dm3
1000
100
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Experiment 37.1
SolutionP. 28 / 37
Calculations
10. (a) Write a chemical equation (Equation 2) for the
reaction between calcium carbonate and dilute
hydrochloric acid.
CaCO3(s) + 2HCl(aq) CaCl2(aq) + H2O(l) + CO2(g)
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Experiment 37.1
SolutionP. 29 / 37
Calculations
(b) Calculate the heat
evolved when
calcium carbonateused in part B reacts
completely with
dilute hydrochloric
acid.
Note
Assume that the specific heat
capacity and density of the
solution are the same as those
of water i.e. 4.2 J g1 K1 and
1.0 g cm3
respectively.
Heat evolved = mcT
=
=
100 cm3 1.0 g cm3 4.2 J g1 K1 2.3 K
966 J
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Experiment 37.1
SolutionP. 30 / 37
Calculations
(c) Hence, calculate the heat evolved when 1 mole of
calcium carbonate reacts completely with dilute
hydrochloric acid.
Number of moles of calcium carbonate used
From the equation, the mole ratio of CaCO3 : HCl
=
=
=
0.030 mol
1 : 2
3.02 g
(40.1 + 12.0 + 16.0 3) g mol1
C l l ti
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Experiment 37.1
SolutionP. 31 / 37
Calculations
Number of moles of dilute hydrochloric acid used
Heat evolved when 1 mole of calcium carbonate
reacts completely with dilute hydrochloric acid
=
is in excess.
=
=
=
=
0.1 mol
HCl
32200 J mol1
32.2 kJ mol1
1.0 mol dm3
dm3
1000
100
0.030 mol
966 J
C l l ti
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Experiment 37.1
SolutionP. 32 / 37
Calculations
11. (a) Write an equation (Equation 3) for the formation
of calcium carbonate from its elements.
Ca(s) + C(s) +2
3O2(g) CaCO3(s)
(b) Draw an enthalpy change cycle linking Equations
1, 2 and 3 together. (Hint: Some other equations
are needed to complete the cycle.)
C l l ti
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Experiment 37.1
SolutionP. 33 / 37
Calculations
2HCl(aq)H1
CaCl2(aq) + H2O(l) + C(s) + O2(g)
H3
CaCl2(aq) + H2O(l) + CO2(g)
H4
H2 2HCl(aq)
Hf [CaCO3(s)]
Ca(s) + C(s) + O2(g) CaCO3(s)23
CaCl2(aq) + H2(g) + C(s) + O2(g)2
3
C l l ti
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Experiment 37.1
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(c) Apart from your experimental results in parts A and
B, what other information is needed to calculate the
standard enthalpy change of formation of calciumcarbonate? Look up these necessary data.
Calculations
The following information is needed to be
found for calculating standard enthalpy
change of formation of calcium carbonate:
1. Standard enthalpy change of formation of
water = 285.8 kJ mol1, i.e. H3
2. Standard enthalpy change of formation of
carbon dioxide = 393.5 kJ mol1, i.e. H4
C l l ti
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Experiment 37.1
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12. By using Hesss Law, calculate the standard enthalpy
change of formation of calcium carbonate. (Assuming
that all reactions were carried out under standardconditions.)
Calculations
Hf [CaCO3(s)]
=H1+ H3+ H4 H2= (416.6) + (285.8) + (393.5) (32.2) kJ mol1
= 1063.7 kJ mol1
S
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Experiment 37.1
SolutionP. 36 / 37
Summary
13. The standard enthalpy change of calcium carbonate is
____________ kJ mol1.1063.7
Q ti
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Experiment 37 1 Solution
Question
14. Explain why the method used in this experiment is not
appropriate for metals that are less reactive than
magnesium.
For those metals less reactive than
magnesium, their reaction towards dilute
hydrochloric acid will proceed more slowly. Theerror due to heat loss to the surroundings will
be larger. The heat evolved in the reaction will
thus be underestimated.