The Medical College - Page 67
126.
A.
Loss of a single electron in the 3s
orbital
leaves the stable electronic configuration of
the
noble gas, neon.
127.
B.
In a neutral atom, the number of electrons
in
orbitals equals the number of protons in
the
nucleus. The latter defines the atomic
number.
128.
C.
Gain of an additional electron would
give
the stable electronic configuration of the
noble
element, krypton.
129.
D.
Note that the number of electrons exceeds
the
atomic number (and the number of protons)
by
one. Thus, this would be an ion with a charge
of
–1.
130.
C.
The fact that the number of electrons is
equal
to the atomic number indicates that this is a
neutral
atom. The fact that the outermost electron is
in the
3p orbital rather than the expected 3s orbital
indi-
cates that the atom is in an excited
state.
131.
D.
Noble elements include helium, neon,
argon,
krypton, xenon, and radon.
132.
D.
Each orbital electron possesses four
quan-
tum numbers--principal, angular
momentum,
magnetic, and spin.
133.
C.
Possible values of magnetic quantum
num-
ber are –1, 0, and +1.
134.
B.
Possible values of spin quantum number
are
+
and –
.
135.
A.
No two electrons in an atom possess all
four
identical quantum numbers.
136.
C.
Silver ions will react with chloride ions
and
precipitate as AgCl.
137.
B.
H2S
2H
+ +
S2–. By the
common ion
effect, lowering the pH (increasing the
H
+ con-
centration) will lower the S
2– concentration
by
displacing the reaction to the
left.
Ki =
If [H
+] increases,
[S2–] must
decrease.
138.
A.
Freezing point depression in water
depends
only on the number of solute particles per
unit
volume
1 M NaCl = 2
1
6.02
10
23 particles per
liter
[H ] [S ]
[H S]
+2
2 ±
2
.
1
2
1
2
0.3 M Na2SO4
= 3
.3
6.02
10
23 particles
per liter
1.5 M glucose = 1
1.5
6.02
10
23 particles
per liter
0.5 M BaSO4
= 2
0.5
6.02
10
23 particles
per liter
Dividing by 6.02
10
23 we can see that the
com-
parative figures are NaCl, 2;
Na2SO4, 0.9;
glu-
cose, 1.5; and BaSO4, 1.0. Thus, the NaCl
solution has the greatest number of particles
per
unit volume (considering the ionization of
NaCl,
Na2SO4, and
BaSO4), and it
will have the lowest
freezing point.
139.
D.
A reaction in which electrons (e
– )
are
removed is termed an oxidation reaction;
the
adding of electrons to an atom or molecule
is
termed a reduction reaction.
140.
A.
The hydronium ion, H3O
+, is a
protonated
water molecule. 2H2O
H3O
+ +
OH–
141.
A.
As long as the volume units are the
same,
N1V1 =
N2V2
142.
A.
This is a definition of the zwitterion;
an
example is the amino acid,
glycine.
WRITING SAMPLE
Part 1, Essay
One must point out that Demonax begins his
assertion
with "probably." The statement then takes on a
more
questioning or probing tone, as if he is asking
for a con-
tradiction. This tone colors an attitude that
is already
filled with a sort of shrugging resignation or
apathy.
Demonax clearly believes that laws do not serve
their
intended purpose. It seems that, to him, that
purpose
would be to change the nature of people who are
not
"good." He says, in effect, that good
individuals do not
need laws in order to be good and that bad ones
will
remain bad with or without laws.
This is probably true. However, it is not clear
that
Demonax explored the possibility that laws
might serve
another purpose. Among some probable other
things,
laws serve as guidelines by which individuals
can oper-
ate in social groups. Even a very good person
might
want to know on which side of the street she
should
drive. Laws might also be a deterrent to bad
behaviors as
well. A bad person who might steal the purse of
an
elderly blind woman might be deterred by the
knowl-
edge that the law calls for a prison sentence
for so doing.
The individual is made no better by the law,
but the life
of the blind woman might be.
V
NV
N
2
11
2
50 0 25
050
==
=
()( .
)
.
25 ml
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