Heating curves and DH

1
Heating curves and DH
2
Heating curves and DH
temperature
added energy
3
Heating curves and DH
melting/ freezing pt
temperature
added energy
4
Heating curves and DH
boiling/ cond. pt
melting/ freezing pt
temperature
added energy
5
Heating curves and DH
boiling/condensing occurring here
melting/freezing occurring here
boiling/ cond. pt
melting/ freezing pt
temperature
added energy
6
How is the total enthalpy change (DH) calculated
for a substance whose temperature change
includes a change in state?
7
temperature
Dt of solid absorbing energy
added energy
8
temperature
DH m x Csolid x Dt
added energy
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the energy absorbed as a solid melts
becomes potential energy, so no Dt
temperature
DH m x Csolid x Dt
added energy
10
DH DHfus x mols
temperature
DH m x Csolid x Dt
added energy
11
Dt of liquid absorbing energy
DH DHfus x mols
temperature
DH m x Csolid x Dt
added energy
12
DH DHfus x mols
DH m x Cliquid x Dt
temperature
DH m x Csolid x Dt
added energy
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the energy absorbed as a liquid boils becomes
potential energy, so no Dt
DH DHfus x mols
DH m x Cliquid x Dt
temperature
DH m x Csolid x Dt
added energy
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DH DHvap x mols
DH DHfus x mols
DH m x Cliquid x Dt
temperature
DH m x Csolid x Dt
added energy
15
Dt of gas absorbing energy
DH DHvap x mols
DH DHfus x mols
DH m x Cliquid x Dt
temperature
DH m x Csolid x Dt
added energy
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DH m x Cgas x Dt
DH DHvap x mols
DH DHfus x mols
DH m x Cliquid x Dt
temperature
DH m x Csolid x Dt
added energy
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DH m x Cgas x Dt
DH DHvap x mols
DH DHfus x mols
DH m x Cliquid x Dt
temperature
DH m x Csolid x Dt
added energy
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The DH of any substance being heated will be the
sum of the DH of any Dt occurring plus DH of any
phase change occurring
DH m x Cgas x Dt
DH DHvap x mols
DH DHfus x mols
DH m x Cliquid x Dt
temperature
DH m x Csolid x Dt
added energy
19
The DH of any substance being heated will be the
sum of the DH of any Dt occurring plus DH of any
phase change occurring
DH m x Cgas x Dt
DH DHvap x mols
DH DHfus x mols
DH m x Cliquid x Dt
temperature
DH m x Csolid x Dt
added energy
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EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
DH m x Cgas x Dt
DH DHvap x mols
DH DHfus x mols
DH m x Cliquid x Dt
temperature
DH m x Csolid x Dt
added energy
21
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
50 oC
temperature
0 oC
-20 oC
added energy
22
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
use the following values Cice 2.1 J/goc,
DHfus H2O 6.01 kJ/mol, CH2O liq 4.186 J/goC
50 oC
temperature
0 oC
-20 oC
added energy
23
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
use the following values Cice 2.1 J/goc,
DHfus H2O 6.01 kJ/mol, CH2O liq 4.186 J/goC
50 oC
DH3 m x Cliquid x Dt
DH2 DHfus x mols
temperature
0 oC
DH1 m x Csolid x Dt
-20 oC
added energy
24
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
use the following values Cice 2.1 J/goc,
DHfus H2O 6.01 kJ/mol, CH2O liq 4.186 J/goC
50 oC
DH3 m x Cliquid x Dt
DH2 DHfus x mols
temperature
0 oC
DH1 10g x 2.1 J/goC x 20oC
-20 oC
added energy
25
DH210 g x 1mol/18g x 6.01kJ/mol
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
use the following values Cice 2.1 J/goc,
DHfus H2O 6.01 kJ/mol, CH2O liq 4.186 J/goC
50 oC
DH210 g x 1mol/18g x 6.01 kJ/mol
DH3 m x Cliquid x Dt
temperature
0 oC
DH1 10g x 2.1 J/goC x 20oC
-20 oC
added energy
26
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
use the following values Cice 2.1 J/goc,
DHfus H2O 6.01 kJ/mol, CH2O liq 4.186 J/goC
DH3 10g x 4.186 J/goC x 50 oC
50 oC
DH210 g x 1mol/18g x 6.01 kJ/mol
temperature
0 oC
DH1 10g x 2.1 J/goC x 20oC
-20 oC
added energy
27
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
use the following values Cice 2.1 J/goc,
DHfus H2O 6.01 kJ/mol, CH2O liq 4.186 J/goC
total DH DH1 DH2 DH3
DH3 10g x 4.186 J/goC x 50 oC
50 oC
DH210 g x 1mol/18g x 6.01 kJ/mol
temperature
0 oC
DH1 10g x 2.1 J/goC x 20oC
-20 oC
added energy
28
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
use the following values Cice 2.1 J/goc,
DHfus H2O 6.01 kJ/mol, CH2O liq 4.186 J/goC
total DH DH1 DH2 DH3 420 J
3340 J 2093 J
DH3 10g x 4.186 J/goC x 50 oC
50 oC
DH210 g x 1mol/18g x 6.01 kJ/mol
temperature
0 oC
DH1 10g x 2.1 J/goC x 20oC
-20 oC
added energy
29
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
use the following values Cice 2.1 J/goc,
DHfus H2O 6.01 kJ/mol, CH2O liq 4.186 J/goC
total DH DH1 DH2 DH3 5853 J 420 J
3340 J 2093 J
DH3 10g x 4.186 J/goC x 50 oC
50 oC
DH210 g x 1mol/18g x 6.01 kJ/mol
temperature
0 oC
DH1 10g x 2.1 J/goC x 20oC
-20 oC
added energy
30
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
It takes 5853 joules to heat up 10 grams of water
from -20 oC to 50 oC.
DH3 10g x 4.186 J/goC x 50 oC
50 oC
DH210 g x 1mol/18g x 6.01 kJ/mol
temperature
0 oC
DH1 10g x 2.1 J/goC x 20 oC
-20 oC
added energy
31
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
It takes 5853 joules to heat up 10 grams of water
from -20 oC to 50 oC.
DH3 10g x 4.186 J/goC x 50 oC
50 oC
DH210 g x 1mol/18g x 6.01 kJ/mol
temperature
0 oC
DH1 10g x 2.1 J/goC x 20 oC
-20 oC
added energy
32
EXAMPLE What is DH for 10 g water with a total
Dt from -20 oC to 50 oC?
It takes 5853 joules to heat up 10 grams of water
from -20 oC to 50 oC.
50 oC
temperature
0 oC
-20 oC
5853 J
added energy