_____
______
1
it. (
‘J/\..
I
t
I
H
5
H
ft’i((
A. Matching
Write the letter of the correct
Match the correct description to each numbered term.
ion on the line.
Column B
Column A
a. the quantity of heat that raises the temperature
of I g of pure water 1C
1. heat capacity
2. law of conseriaflon of energy
b. the change in enthalpy that accompanies the
formation of I mole of a compound from its
elements, with all substances in their standard
states at 25CC
c. energy that always flows from a warmer object
to a cooler object
3. heat of reaction
5ding
roun
0
s
d. a process that loses heat to the
4. energy
—
21. Which of the following statements is true?
a.
=
c.
is always negative.
b. IH 1
sohd
d. H,,sd is always positive.
5. calorimeter
e. the amount of heat requited to change the
temperature of an object by exactlY 1’C
6. specific heat
f. the capacity to do work or to supply heat
7. heat
g. the heat absorbed Ot released by a chemical
reaction
8. standard heat of formation
22. How much heat, in kJ, is required to melt 54.0 of
g ice at 1CC into water
atffC if H
5 for water = 6.01 kJ/rnol?
a. 0.111k)
c. 18.OkT
b. 325 kJ
d. 8.99 kI
23. How much heat is required
to cnnvert 9.00 g of water at luff
C into
steam at lOffC, if
for water = 40.7 kJfmol?
a. 20.4k)
c. 18.0k)
b. 366k)
d. 81.4kj
24. If the molar heat of solution
of 3
NO is 25.7 kjlmol, how muc
4
NH
h heat
(in kJ) would be required to dissolv
e 20.0 g of 3
NO in water?
4
NH
a. 103k)
c. 0.250k)
b. 514 kI
d. 6.43 kJ
25. Calculate the enthalpy chan
ge, IH in kJ, for the reaction
0(s)
2
H
(g) + O,)g)
2
l-I
Use the following:
(g) + O
2
H
(g)
2
0(l)
5
H
= —285.9 kJ
1-1,0)5)
H,O(l)
= ±6.0 1<1
a. -291.9k)
c. —279.9 k
b. -291.9kJ
d. ±279.9k)
-=
-
—
h. the amount of heat required to raise the
temperature of I gram of a substance 1”C
9. calorie
1. In any chemical Ot physical process energy is
neither created nor destroyed
10. exothermic process
a device used to measure the amount of heat
absorbed Ot released during chemical or
C. Essay
Write a short essay for the following.
26. Distinguish between endo
thermic and exothermic processes
. Give at least three
examples of each that you enco
unter in everyday life.
B. Multiple Choice
Choose the best answer and write its letter on the line.
me SI unit of energy is
1
ule.
c. o
d. enthalpy.
a. heat capacity
t,. calorie.
12. How many calories are required to raise the temperature of 75,0 g of
water from 20’C to 50’C?
a. 1.50 2< i0 cal
c. 3750 cal
b. 2250 cal
d. 75.0 cal
—
13. If I Calorie = 4.18 1<), how many k) of energy can be released by an
apple containing 125 Cal?
a. 0.0334 1<)
c. 522 kJ
b, 299k)
d. 5.222< lO
kJ
t
14. The temperature of a 6.0-g sample of glass changed from 20’C to 45’C
when it absorbed 550 1 of heat. What is the specific heat of this glass
sample?
a. 37J/g.’C
c. 2300)fg.C
b. 0.27 1/g.C
d. 130 j/g.C
D. Problems
Solve the following problems in the
space provided. Show your work.
27. Determine the specific heat
of a material if a 12-g sample abso
rbed 961 as it
was heated from 21CC to 41CC,
15. ‘rhe enthalpy of a system is the same as its:
a. specific heat.
c. heat of combustion.
b. heat of reaction.
d. heat content.
16. When your body is warmed by an electric blanket during the winter
this process is said to be
a. endotherutic.
c. isotherrnic.
b. exothermic.
d. none of the above
17. A student mixes two water solutions with an initial temperature of
25.0’C to form a final solution with a mass of 65.0 g at 30.1CC. What is
the heat change, in kJ, for this reaction?
a. 325kl
c. 1.36k)
b. 272 kI
d. 1.95k)
18. Given the equation 2Mg(s) 0
(g)
2
following is true?
a. The reaction is endothermic.
b. .I.H = —72.3 kJ
—
2MgO(s)
-
28. If 22 0 mL of water containing 0.030 mol of HCI is mixed with 38.0 mL of water
containing 0,030 mol of NaOH in a calorimeter such that the initial temperature
of each solution was 27.0’ C and the final temperature of the mixture is 35.1CC,
how much heat (in kJ) is released in the reaction? Assume that the densities of
the solutions are 1.00 gImL.
72.3 ki, which of the
c. .IH = ‘-72.3 k)
d. The reaction absorbs heat.
(s)
3
0
5
ZFe(s)
29. Given the equation 3C0(g) + Fe
heat is released when 56.0 g of CO react?
—
—
19. Given the equation in question 18. how much heat is involved
production of 5.0 mol of MgO?
a. 36k)
c. 360k)
b. 72k)
d. 180k)
20. Given the equation Si(s) 2C1,(g( — 2
S1C
(
g)I
SiC
(
2
fil
much heat is produced when 106 g of Cl
2 react?
7,281
k
a. 4
X10
C. 360k)
b. 513k)
d. 180k!
—
±
in
the
687 k), how
±
2
3C
(
g)
0
+
24.7 k) how much
heat is
can be frozen into ice at 0C if 55.0 kJ of
30. How many grams of water at 0C
kJ/mol
=
—6.01
for water
removed?
kJ, for the following reaction?
31. What is the enthalpy change, MI in
s)
(
2
2MgCI
+
U) — Si(s)
4
2Mg(s) + SiCI
Use the following:
1H = —687 kJ
(l)
4
(g) —* SiCl
2
Si(s) 2C1
tsH = —641 kJ
(s)
2
MgCI
(g)
2
Mg(s) + C1
(.I-1°) for the combustion of ethane,
32. What is the standard heat of reaction
water? Write the final balanced
(g). to form carbon dioxide gas and
5
H
2
C
equation for the reaction.
Standard heats of reaction:
C,H —84.68 kJ
6
O,(g) = 0.0 kJ
-393.5 ItT
(g)
2
C0
0(ll —285.5 kJ
2
H
Oh.
I
Vueuu
jta,
jyuju
q
1
D.Problenis
A. Matching
i.e
2.i
3.g
4.
5.)
6.h
7.c
8.b
9.a
i0.d
27. Specific heat
=
12 g x 20CC
0.40 J/(g x C)
28. MI=mxCxT
B, Multiple Choice
ii.c
12.b
13.c
14.a
15.d
=
16.a
17.c
i8.b
19.d
20.b
(60.oP x 1.0o)x (4.l8__-!__)
=
21.b
22.c
23.a
24.d
25.b
C. Essay
26. Endothermic processes absorb heat, while
heat.
release
processes
exothermic
Endothermic examples include the melting
of ice, the evaporation of a puddle, the
sublimation of mothballs, and the heat used
to cook food. Exothermic examples include
the combustion of fossil fuels such as
gasoline, the cooling of skin as perspiration
evaporates, and the freezing of water.
x (35.0CC 27.O’C)
60,0k X 4.i8J
X 8.0
—
—
-
—---—-
2.0x iO
Jor2.OkJ
3
=
29. 56.0 gCO x
Lmel-eO
24.7kJ
x
i6.5kJ
=
30. 55.01x.x
i8.0g1
165g
31. 2[Mg(s) + C1
() — MgCI,(s)) 2(iH = —641 kJ)
2
(l
4
SiCl
(g AH = ± 687 kJ
2
Si(s ÷ 2C1
2Mg(s) + SiCI
(O —* Si(s) ± 2MgC1
4
(s
2
H= —1282k) ± 687kJ = —595kJ
—
32.
)
±°
(
2
=
—
0
g)
C
2
(
3FlO(l)
1J1 (products) — M4 (reactants)
[2(—393.5 kJ) + 3(—285.8 kJ)J
[(—84.68J) + (0.OkJ)J
—l559.7kJ
—
=
+