KEY 2

Hess’s Law Worksheet
4 (g)
H
2
for the reaction: C
1. Calculate
+
2 (g)
H
—*
6 (g), from the following data.
H
2
C
\1-I4ILkJ
0
)
H
30
l
i2C
H
+
f2
(
g)
g)—
C
4
(
(
2
0
.,Z
6 (g)
CH
(
g)+
H
(
2
2.
+
3Y2 02 (g)
1/202
—*
2 (g)
2 CO
3 H0 (1)
+
=
/
(g)-+ 1-120(1)
(g)
O
2NO
g)+
g)—
(
2
N
(
+
5 02 (g)
—*
4 NO (g)
02 (g)
—*
C (s)
+
+
zH
0 (g)
2
2H
02(g)
2 02 (g)
—*
—*
0 (g), from the following data.
2
6H
AH-91.8kJ
g)
2H
(
3. Find zH° for the reaction 2
data.
H (1)
C
O
5
H
2
+
AH-180.5kJ
/
H
)
3H
*2N
g
g)+
g)—
3
(
N
(
2
(
+
-285.8 Id
tH
3 (g)
Calculate \H for the reaction 4 NH
2H
2 (g)
-1560. kJ
+
2C(s)
2 (g)
2 CO
+
+
02(g)
—*
=
H(l), using the following thermochemical
C
O
5
H
2
0 (I)
2
2H
=
2 (g)
CO
zIf
-
0
)
*H
Y2
(l
g)+
g)—
H
(
2
O
P
—-i
—*
HCN (g)
+
I
-875. Id
-394.51 Id
AH=-285.8kJ
-
3 (g)
4 (g)+ NH
4. Calculate zH for the reaction CH
-483.6 Id
/
-
2 (g), given:
3H
A
H
)
3H
*2N
g
g)+
g)—
3
(
N
(
2
(
zH=-91.8kJ
/
H
H
)
)+2
g
g)C
4
C(s
(
2
(
H-74.9Id
(g)
N
s)+
*2HCN
g)+2C(
(g)—
H
(
2
AH=+270.3kJf—
—
(
2 (g)
5. Calculate tH for the reaction 2 Al(s) + 3 Cl
—+
3 (s) from the data.
2 AId
-
1
)
3H
>2A1C
(aq)—
)+
g
+6HC1
aq
2
2A1(s)
(
3
(
HCI (aq)
HC1 (g)
—>
2 (g)
H
2 (g)
Cl
+
3 (s)
Aid
—*
—*
2 HCI (g)
3 (aq)
AIC1
AH=-1049.kJ
M-1 = -74.8 Id
AH
H
=
-1845. Id
-323. Id
! Gi
-‘
Ch 14 Questions: Heat of Fusion and Heat of Vaporization
Specific Heat (Cp)
Water (1420)
Ethanol (C
OH)
5
H
2
Mercury (Hg)
Heat of Fusion
)
11
(i.Hf
6.00 kJ/rnol
5M2 kJ/mol i(4
2.29 kJ/mohz.
4. 18 J/g °C
2.44 JIg °C
0.14 JIg °C
1) How much heat is required to
HeaL
of Vapenzation
(L\}
v
4
ap)
40.6 Id/mol
38.6 kJ/moli31
59.1 kJ /mol 4
r
the temperatureof 20 grains. çf water by 26 °C?
2.; j
2) How much heat is required to melt 2.5 moles of ice?
i2
7
/ 7) Ad..)
3) How much heat is transferred w1 57 grams of mercury cools froin76
°C to 18 °C
4) If you have 27
water 9
vapor
increase
grams of 100°C liquid water, how much heat is-re4tiiftdToturn it into
\\
5) How much energy is transferred when 70
7 z
grams of ethanol is 1iated from 21 °C to 68
6(’
6) How much heat is transferred when 400
grams of mercury (Hg)
J
aporized?
‘I? Z )
(
7) How much heat is transferred when 400 grams of mercury is coo1cd
om-280 °C to 30
/
)
£
Ij
8) How much heat is transferred when 230
grams of eth Fis1ozen2—
9) How much heat is transferred when 100
9
liquid
grams of ethanol condenses from a gas tga
?
10) How much heat is transferred when 1 mole of mercury is heated
from 80 °C to 125
°C
1
11) How much heat is required to melt 40 grams of ice anahericr
e1ts temperature
fromO°Cto25°C?
L17 ,j
..
12) How much heat is required to heat 2 moles of water from 25°C
to its boiling point
and then turn it into water vapor?
,‘/,3 kT
/ 7_
-
13) How much heat is required to melt 50
thenturnitintovapor?
I”
grams of ice, heat it to its boiling point, and
-
.
;
‘i
tr
//7f
—
is—a
14) The boiling point of ethanol is 78°C. How much heat is require
d to heat 100 grams
of ethanol from 25°C to its boiling point and then to turn it into a
vapor?
i
t
‘

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