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CHEM105

Practice Final Exam Key

Name

Fall 2013

Key

Please ignore all point values on this Practice exam as they are all incorrect
...
997x108ms-1
1 J = 1 kg∙m2∙s-2
mass of e-: me=9
...
626x10-34 J∙s
charge of an e-: e = 1
...
67x10-27 kg
Avogadro’s constant: NA = 6
...
08206 L atm mol-1 K-1= 8
...
The degree of agreement among several measurements of the same quantity is called __________
...

a) accuracy
b) error
c) precision
d) significance
e) certainty
2
...
Which of the following atomic symbols is incorrect?
14
a)
6C
37
b)
17 Cl
32
c)
15 P
39
d)
19 K
14
e)
8N
4
...
8 g
...
Phosphorus has the molecular formula P4, and sulfur has the molecular formula S8
...
88 g of sulfur?
a) 3
...
263 g
c) 7
...
88 g
e) none of these
6
...
You
add a dilute solution and the bulb grows dim
...
The correct set of coefficients, respectively, for the balanced reaction
is:
a) 3 6 6 3 4
b) 8 6 5 10 5
c) 5 10 10 5 5
d) 1 2 2 1 1
8
...
0-L flasks contain the gases He, Cl2, CH4, and NH3, each at 0°C and 1 atm pressure
...


Which gas has the highest density?
a) He
b) Cl2
c) CH4
d) NH3
e) all gases the same

10
...
If the volume of the container cut in half, which gas will have the highest pressure?
a) He
b) Cl2
c) CH4
d) NH3
e) all gases the same
12
...
How many electrons in an atom can have the quantum numbers n = 3, l = 2?
a) 2
b) 5
c) 10
d) 18
e) 6
14
...
In which group do all the elements have the same number of core electrons?
a) P, S, Cl
b) Ag, Cd, Ar
c) Na, Ca, Ba
d) P, As, Se
e) none of these
16
...
Equilibrium is reached in chemical reactions when:
a) The rates of the forward and reverse reactions become equal
...

c) The temperature shows a sharp rise
...

e) The forward reaction stops
...
At a given temperature, K = 0
...
033
30
...
00109
33
920

PCl5(g)?

Fall 2013

CHEM105

Practice Final Exam Key

Fall 2013

19
...

a) are infinite; is one
b) is one; are infinite
c) is one; is one
d) are infinite; are infinite
e) none of these
20
...
If HCl is added, which ion will
react with the extra hydrogen ions from the HCl to keep the pH from changing to a large extent?
a) OH–
b) Na+
c) F–
d) Na–
e) none of these

21
...
Which are the correct signs
of the following terms:
a) H = (-),
=(-), q=(+),
=0,
=0,
=(+)
b) H = (-),
=(-), q=(-),
=0,
=0,
=(+)
c) H = (-),
=(-), q=(+),
=0,
=0,
=(-)
d) a) H = (-),
=(-), q=(-),
=0,
=0,
=(-)
e) none of these
22
...

Which undergoes the smallest change in temperature?
a) The metal with the higher heat capacity
...

c) Both undergo the same change in temperature
...

e) You need to know which metals you have
...
What is
the net ionic equation for the reaction that occurs when a small amount of sodium hydroxide is
added to the buffer?
+
a) NaOH(aq) + H3O+(aq
(aq) + 2H2O(l)
+
–
b) H3O (aq) + OH (aq
2O(l)
–
c) OH–(aq) + HCHO2(aq
2 (aq) + H2O(l)
d) NaOH(aq) + HCHO2(aq
2(aq) + H2O(l)
+
e) Na (aq) + HCHO2(aq) NaH(aq) + HCO2+(aq)
25) In titrating 0
...
20 M NaOH at 25°C, the solution at the equivalence
point is
a) 0
...
10 M HCl and 0
...
10 M NaCl

26
...
The neutralization of hydrochloric acid with sodium hydroxide
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The reaction of iron copper metal with silver (I) ions to produce copper (II) ions and silver metal
...
The mixture of a 20 mL of a 2 M solution of lead (II) nitrate with 15 mL of a 1
...

Pb2+(aq) + SO42-(aq)  PbSO4(s)
Precipitation reaction
D
...
5 M sodium chloride and 20 mL of 0
...

NR

CHEM105

Practice Final Exam Key

Fall 2013

27
...

[

][

]

[

]

b) At equilibrium the concentration of SO3(g) is 0
...
75M and O2(g) is 0
...
66 atm

What will happen to the numbers of moles of SO3 in equilibrium with SO2 and O2 in the reaction
d) Oxygen is added
...

Increase (less moles of gas on reactants side, thus shift that way
...

No effect
...

g) The temperature is decreased (the reaction is endothermic)
...

Decrease (shift toward products)
...
Use a chemical
reaction if possible
...
A chemical reaction for this
process for generic element X is (X(g) + e-  X-(g)
...

(b) Why is it useful to state the trend of electron affinity as becoming more negative as we move from
left to right across the periodic table?
The electron affinity is an energy released, exothermic processes have negative values of energy
...

Consider the graph below to help answer the following questions:
1800

Ionization Energy (kJ/mol)

1600
1400
1200
1000
800
600
400
200
0
Na

Mg

Al

Si

P

S

Cl

Ar

K

Element

(b) Explain why there is an general increase in ionization energy from sodium to argon
...
(NOTE: A common misconception among students
is to say that argon has the highest ionization energy because it has a “filled outer valence shell
...

Electron shielding has increased, so there is a weaker pull on the valence electrons in potassium,
which leads to decreased ionization
...

P:[Ne]2s22p3, S:[Ne]2s22p4 – the 4th electron in S’s valence shell must be paired in an orbital which
increases repulsion reducing ionization energy even with a rise in nuclear charge
...
The reason for both is electronic shielding
...
Elemental analysis is done on a liquid compound containing only carbon, hydrogen and oxygen
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2 % C and 13% H
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A
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(

)

EF = C2H6O, MM(EF) = 12*2+6+16 = 46 (within range)
MF = C2H6O
B
...

C2H6O(l) +

O2(g)  2CO2(g) + 3H2O(g)

C
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0 g of the compound is burned in a sealed vessel containing 168
...
How many grams of excess reagent will be left after the reaction is finished?
grams CO2 not produced= 154 g – 109 g = 45 g CO2

There will be 49
...


CHEM105

Practice Final Exam Key

Fall 2013

30
...


( )

A
...
0x10-19J
...
00x10-7m=400x10-9m=400 nm
(6 points)
B
...
0x10-19J) be able to break an oxygen (=242 nm
needed) or ozone (=320 nm)? How do you know?
The light will not be able to break both molecules because it is lower energy
...
What is the bond dissociation energy of a C-Cl bond in CCl2F2(g)?
The bond dissociation energy is the energy required to break 1 mole of a specific bond
...
0x10-19 J to break a single bond, a mole of bonds would require
5
...
02x1023 bonds/mole = 299 kJ/mol
4 points
D
...
68 kJ/mol and CCl2F2(g) is -477
...

From the reaction:
( )→

( )

( )

we know that
Hrxn= DHo(C-Cl)= Hf0(Cl) + Hf0(CClF2) - Hf0(CCl2F2)
Thus,

Hf0(CClF2) = DHo(C-Cl)- Hf0(Cl) + Hf0(CCl2F2) = 299 kJ/mol – 121
...


If use number given,
Hf0(CClF2) = DHo(C-Cl)- Hf0(Cl) + Hf0(CCl2F2) = 320 kJ/mol – 121
...
a
...
0 M NaOH to
reach the end point and has a pH of 4
...
What is the Ka of acetic acid?
At ½ equivalence point, pH=pKa, so Ka = 1
...
What is the starting concentration of acetic acid?
0
...
0 mol/L = 0
...
09 mol/0
...
5M

c
...
0x10-5 and 1
...

HA(aq) + H2O(l) ⇌ A-(aq) + H3O+(aq)
I
1
...
5-x
x
x
[
+

][
[ ]

]

[ ][ ]
[

]

[

]

-3

x=[H3O ] = 5
...
5x10-3) = 2
...
What is true at the equivalence point of the titration? What kind of problem would you solve to
determine the pH at this point?
At the equivalence point, the moles of initial acid are equal to the moles of OH- added, so all of the initial
HA has been converted into A-
...


e
...
Why is this
true? What is true about the solution at this time?
As we add OH- it reacts to produce A-, so we have a mixture of HA and A-, which is a buffer
...

(a) Calcium carbonate has a Ksp value of 5
...
What is the molar solubility of Calcium
carbonate at 25oC?
Ksp=5
...
07x10-5M

(b) A major concern to the rising of CO2(g) levels is ocean acidification
...
Use chemical reactions to assist your answer
...


(c) As more CO2(g) dissolves in the ocean, will calcium carbonate become more or less soluble? Why?
An increase in pH will drive the final reaction towards the reactants and remove CO32-(aq) from the
solution
...


(d) Solid calcium carbonate can go through the following chemical equilibrium:
CaCO3(s) ⇌ CaO(s) + CO2(g)
Which has Kp=1
...
oC
...
1-gram sample of CaCO3 is put into a 10
...
°C
...

Molar
mass
PCO2

→

nCO2

→

nCaCO3

→

%



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