Download Practice Test #1

CHEM
HOUR EXAM II
1021
10/25/00
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A
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A
Pleaseindicate the correct answer for each question. Each question is worth 5 points. There is only
one correct answer per question. Questions with more than one answer will receive no credit. No
partial credit will be given. Scratchwork doesn't count, right or wrong! No answers given in the
blue books will be counted.
Some Possib~v
Us~{ul
11?{ormation:
Partial Pressure:
Mole Fraction:
PT = PJ + P2 + PJ+
Universal Gas Constant:
0.08206 atm 1/mo1/K
8.314 J/mol/K
Ideal
(7)1/2
Graham's Law
(Rate r)/(Rate2)=
(M2/ Ml)I/2
LlE=q+w
Expans i on/ Corn pres si on
Work (Against Constant P):
w = -PL\V
Enthalpy:
H=E+PV
Heat:
q=smL\T
Light:
c=
E=
A=
Ay
c=
3.00x108 mls
hy
h=
6.626x
h/mv
me=
9.11x10-31 kg
Kinetic
Theory:
First Law of
Xi = nj/nT = Pj/PT
=
(3RT/M)1/2
Thermodynamics
DeBroglie wavelength:
NOTE: A PERIODIC TABLE IS ATTACHED
Molar Volume @ STP
1 atm = 760.00 torr
Gas
Law:
22.4 liters
PV = nRT
TO THE BACK OF THIS EXAM.
10-34 J s
'!. \"S ,L
1
A sample ofhelium~
will
(a)
(b)
c!f;p
(e)
it occupy
1"2,q (, \l.
occupies
12.41iters
at 40. °C and 1.20 atm?
11 V,
v\--:~
liters
-1'<. T,
0.488
6.28 liters
12.4 liters
10.4 liters
17.2 liters
at 2:r:C
;
(I. (2. T 1..
v")..:
I ' lo
~
= 10.4
2.
A gas mixture
and 0.956 atm. What volume
c~
-{
is prepared by mixing
1.0 moles of gas A,
2.0 moles orgas B, and
3.0 moles ofgas C.
The final pressure is 15 atm. What is the partial pressure of gas B?
?
'
0., o )
~ -1.0
+-i,~+
310)
(a)
2.0 atm
\1 = "';i'1? :; ~
~
'lC5
(d)
(e)
3
5.0
6.0
7.0
10.
atm
atm
atm
atm
.=-- 01
$
33
Yl\'3;
-
)'1.,...
'P-r
=.,
?=t?=
Which of the following is not an assumption of the kinetic theory of gases?
~
(b)
( c)
(d)
(e)
The average velocity of the gas particles is directly proportional to the
pressure.
Gas particles are very small compared with the average distance between
particlesGas particles collide with the walls of their container and in doing so give
rise to pressure.
Gasesare made up of tiny particles in constant, chaotic motion.
Gas particles do not interact with one another.
4.
Gaseous C2~ reacts with O2 according to the following
equation:
C2H4(g) + 302(g) ~ 2CO2(g) + 2H2O(g)
What volume of oxygen at STP is needed to react with 1.50 mol of C2H4?
l
'\
'3~((.
~~
I , .«;.'-0 ~0\(
C1..1-1'1 I ~
-Lf.~-o
Mo
(a)
4.50 liters
, htr>f~
Ca./~1I
(b)
33.6 liters
"2. "2 I 4 ...e
><..Q
(1£D
10lliters
=?
)( .:
.AT
~TP
( d)
67.2 liters
4 ' l'"() ('lA 0 ,
I.()O rn,1
(e)
85.0 liters
5
/"
"'-'1...
10
I
..1<.
Which of the following gases would have a higher rate of diffusion than C2H2
under the same conditions of temperature and.RJltessure?
II
~.
r')1"br fVI,4t ,f
"
N2~1.~
IJuLl..ol..,1e
.1
; 24+1..:2.'
(a)
(b)I
a2
C12
~
Cll4
~
CO2
~ ~
~
"1 f
v\olola. ,.. I)oItA' l'
~~\.
~
,
I (.-.
-/...IL-l
A sample ofN2 gas is mixed with a gas (A) of unknown molar mass. The partial
pressures of each gas are known to be 200. torr. The gases are allowed to effuse
through
a pinhole
and itofisAfound
that gas A escapesat three times, tl.Ie rate of N2.
What is the
molar mass
?
6.
1
(1;1)
(b)
(c)
(d)
(e)
3.11
252
84.0
9.33
2.00
\~1S
R~
.:
-, -
3p
==
--(\I\
('FJ~
)
)(.
::~
~<A)
I1Atc.. u~
9,0
t 'C'",I...J
-
'::-
~
~
)( : 3,
~
At 100QoC, and a pressure of 10. Torr, the density of a certain element in the
gaseous state is 2.9 x 10-3 g/liter. What is the element? (Remember that there is a
periodic table at the end of the exam. Also, please be careful with your units.)
7,
~=
(a)
cf?
(e)
d."li-
Ne
He
Na
Ar
Hg
(tIt
1tA.=- ~
=-~
p
~
(i
~
"2~
d l().td
0 ftot-r
).
Consider the two samples of gas shown below:
8.
0
I~
Sample
A
Sample
T = 300 K
p = 1 atm
2
Cc-~
B
T = 300 K
p = 2 atm
V= 1.01iter
V= 1.01iter
Which of the following statementsis true?
J:ar
J:br
There are more atoms in Sample A than in Sample B.
Ja~;~rl
The argon atoms in Sample B have, on average, more kinetic energy than
I
the xenon atoms in sample A.
The density of Sample A equals the density of Sample B.
The number of moles is the same in both samples.
Xenon atoms in Sample A are moving, on average, slower than the argon
atoms in Sample B. ~ I :--"'\'/l..=I'i"PT
I
.,1J " Ii(
-"'\...u..'). )
, ~
J
/V\~ ~
,4
~
W@
9.
Consider the following
properties of a substance:
\£.
I.
mass
V
II.
i
III.
temperature
volume
v
IV.
concentration
""
V.
energy
(moles/liter)
Which of these is(are) intensive?
(a)
@
(d)
(e)
10.
I, III, and V only
II only
II and IV only
III and IV only
I and V only
Calculate the change in energy associated with the expansion of a gas from 152
liters to 189 liters against a constant pressure of 14 atm. Assume that no heat is
exchanged in the process, and be sure to apply the same sign convention we
adopted in class.
~ r/°
i') .1
b.Eh+\..(J
=-\Dv
520 liter atm
(a)
I~Cf~
-/,.s-2-R.
) :
-520 liter atm
@1)
= -( I ~ ~~ )
-260
liter
atm
(c)
175 liter atm
(d)
.: -(
ty ~~
)
260
liter atm
(e)
Which of the following will cause py to be less than nRT for a real (non-ideal)
gas?
11.
(a)
(b)
Some molecules in the sample have speedsless than the average speed.
Some molecules in the sample have speedsgreater than the average speed.
The gas molecules have a very low molecular mass.
The gas molecules attract one another.
None of these.
Which of the following statementsabout ozone is incorrect?
12.
(a)
(b)
CW
(e)
The chemical fomlula of ozone is 03.
Ozone can be found as a trace gas in both the stratosphere and in a
polluted troposphere.
Ozone is an important greenhousegas in the troposphere.
The ozone layer is found in the stratosphere.
Ozone participates in the fomlation of photochemical smog.
Consider the reaction
13
C2HsOH(I)
+ 302(g)
~
2CO2(g)
+ 3H20(1)
For the reaction as written, ~H = -1370 kJ. When a 15.1 9 sample of C2HsOH is
burned at constant pressure, how much energy is released as heat? The molar
mass of C2HsOH is 46.1 g/mol.
~
1.5"".lq
I.J.W
(b)
(c)
(d)
(e)
449
2250
0.449
1020
196
kJ
)(
o
kJ
kJ
kJ
kJ
~~\(.
~ Mf>(
4
'
(
~
J=-
o.$2i'
()?u
.12
C').I.JrC:>H
~
lJ'1o1
I
c1.I.JroH
==-
\ s 70
t.(. :r
~
'}( = 4 L-/q 1<:4"
For a particular
14.
process, q = 20 kJ and w = 15 kJ. Which
of the following
statements is(are) true?
~
UJ
~
Heat flows from the system to the surroundings.
The system does work on the surroundings.
L\E = 35 kJ
~
(e)
All of the above are true.
None of the above are true.()
b
rh
\.Y-1
£ :::-7 +- L<) :
'3 s- I<.T
5
Given the following thernlochemical data:
H20(1)
~Ho
---,-f
-286
HC1(g)
-92 kJ/mol
Substance
kJ/mol
Calculate the standard enthalpy change, ~Ho, for the reaction
CI2(g) + H20(1) ~ 2HCl(g) + (1/2)02(g)
O
-2~'
-,')..
0
102.
(£L
(@1::::>
(e)
16,
is given.
Which of the following correctly represents the reaction for which fj.H is the
standard molar enthalpy of formation of NaCl(s)?
@
(c)
(d)
(e)
17.
471 kJ
1O2 kJ
Not enough information
/t...J-
Na(s) + Cl(s) ~ NaCl(s)
Na(s) + (1/2)CI2(g) ~ NaCl(s)
2Na(s) + Clig) ~ 2NaCl(s)
NaCl(g) ~ NaCl(s)
NaOH(aq) + HCl(aq) ~ NaCl(aq) + H20(1)
How much heat is required to raise the temperature of a 6.21 9 sample of iron
(specific heat = 0.450 1/g/°C) from 25.0 °C to 79.8 °C?
'
J
(a)
70.01
(b)
(c)
1011
3861
Ar=-S"4.t°<:..
{;
:
r
...
-
.=:
IS":?
~
Consider the following hypothetical reactions:
18.
A+B
~
AH = 200 kJ
2C
L\H
E-tC
= -50
kJ
What is Llli for the reaction
A+B~2E
(b)
150 kJ
(c)
250 kJ
(d)
-250 kJ
(e)
-150kJ
A typical
~
.le
(a)
)
(c)
(d)
(e)
20.
+ loO
t:,.H=?
300 kJ
~
19,
"200
wavelength
-"'?' 2
for infrared
photon ofinfrared
2.0x10-19J
6.6 x 10-26J
25
1.5 x 10 J
6.6x 10-4°J
3.0x 102 J
radiation
E
is 1.0 x 10-6 m. What is the energy ofa
radiation ofthis wavelength?
(CI. \
E = ~v:"""' \ 1'\ I ~
-~(.f J-.'
(
I."
)CIO
3.00)(IO
("" / I A
,c;(,J1"J
-'9': 2.0 )('IO ~
-r..j),f;)
Which of the following statements concerning the Bohr model of the hydrogen
atom is incorrect?
(a)
(b)
(c)
States with higher values of n have higher energy .
States with higher values of n have larger radius.
When a hydrogen atom absorbs energy, the value of n increases.
The nucleus and the orbiting electron attract one another .
The ground state of a hydrogen atom has n = 0.