Consider the dissolution of CaCl 2 : CaCl 2 ( s ) → Ca 2 + ( a q ) + 2 Cl − ( a q ) Δ H = − 81.5 KJ An 11.0-g sample of CaCl 2 is dissolved in 125 g water, with both substances at 25.0ºC. Calculate the final temperature of the solution assuming no heat Joss to the surroundings and assuming the solution has a speci.fic heat capacity of 4.18 J/ºC · ·g.
Consider the dissolution of CaCl 2 : CaCl 2 ( s ) → Ca 2 + ( a q ) + 2 Cl − ( a q ) Δ H = − 81.5 KJ An 11.0-g sample of CaCl 2 is dissolved in 125 g water, with both substances at 25.0ºC. Calculate the final temperature of the solution assuming no heat Joss to the surroundings and assuming the solution has a speci.fic heat capacity of 4.18 J/ºC · ·g.
Solution Summary: The author defines the heat capacity C as the ratio of heat absorbed to the temperature change.
CaCl
2
(
s
)
→
Ca
2
+
(
a
q
)
+
2
Cl
−
(
a
q
)
Δ
H
=
−
81.5
KJ
An 11.0-g sample of CaCl2 is dissolved in 125 g water, with both substances at 25.0ºC. Calculate the final temperature of the solution assuming no heat Joss to the surroundings and assuming the solution has a speci.fic heat capacity of 4.18 J/ºC··g.
LTS
Solid:
AT=Te-Ti
Trial 1
Trial 2
Trial 3
Average
ΔΗ
Mass water, g
24.096
23.976
23.975
Moles of solid, mol
0.01763
001767
0101781
Temp. change, °C
2.9°C
11700
2.0°C
Heat of reaction, J
-292.37J -170.473
-193.26J
AH, kJ/mole
16.58K 9.647 kJ 10.85 kr
16.58K59.64701
KJ
mol
12.35k
Minimum AS,
J/mol K
41.582
mol-k
Remember: q = mCsAT (m = mass of water, Cs=4.184J/g°C) & qsin =-qrxn &
Show your calculations for:
AH in J and then in kJ/mole for Trial 1:
qa (24.0969)(4.1845/g) (-2.9°C)=-292.37J
qsin =
qrxn =
292.35 292.37J
AH in J = 292.375 0.2923kJ
0.01763m01
=1.65×107
AH in kJ/mol =
=
16.58K
0.01763mol
mol
qrx
Minimum AS in J/mol K (Hint: use the average initial temperature of the three trials, con
Kelvin.)
AS=AHIT
(1.65×10(9.64×103) + (1.0
Jimai
For the compound: C8H17NO2
Use the following information to come up with a plausible structure:
8
This compound has "carboxylic acid amide" and ether functional groups.
The peaks at 1.2ppm are two signals that are overlapping one another.
One of the two signals is a doublet that represents 6 hydrogens; the
other signal is a quartet that represents 3 hydrogens.
Vnk the elements or compounds in the table below in decreasing order of their boiling points. That is, choose 1 next to the substance with the highest bolling
point, choose 2 next to the substance with the next highest boiling point, and so on.
substance
C
D
chemical symbol,
chemical formula
or Lewis structure.
CH,-N-CH,
CH,
H
H 10: H
C-C-H
H H H
Cale
H 10:
H-C-C-N-CH,
Bri
CH,
boiling point
(C)
Сен
(C) B
(Choose
Chapter 7 Solutions
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