Inorganic Chemistry (XXXXX)

College of Technology (COLTECH)

Semester: First Semester

Level: 200

Year: 2013

Answers (200 )
CONTINUOUS ASSESSMENT BSCP1105: APPLIED INORGANIC CHEMISTRY
First Semester 2013-2014
Time Allowed: 2 Hours Marked/30
Student’s name……..…..………………………………….……..…………………………………………
Matricule number………………………................................ Series………………………………………
SECTION A
Instructions: answer by indicating T for true and F for false at the end of each proposition.
Questions 1: (2 marks)
Why is electron addition unfavourable for the following two electronic configurations?
ns
2
np
0
+ e
-
ns
2
np
1
ns
2
np
3
+ e
-
ns2np
4
1. The ns orbital is full; electrons need more energy to get into np orbital.
2. The process is favourable, because the np
0
orbital is empty available for electrons to come in.
3. The np
3
is half filled; an incoming electron will face repulsion from the electrons already residing
there, so needs extra energy to enter.
4. The addition of electrons to a non-metal needs much energy.
5. The addition of electrons to a metal needs much energy.
6. This is because the Pauli Exclusion Principle is disobeyed.
Question 2: (2 marks)
Using the VSEPR, theory proposed by Gillespie, where (A) central atom (B outer atom) (E) electron pair;
respond to the following:
1. The molecule NH
3
is of the type AB
2
E.
2. The molecule SiH
4
is of the type AB
4
.
3. The molecule CO
2
is linear.
4. The molecule CO
3
2-
is triangular.
5. The molecule NH
3
is of the type AB
3
E.
6. The molecule H
2
O has a bent shape and bond angle of <109.5ﹾ
Question 3: (2 mark)
Using the orbital nomenclature and following the azimuthal quantum number 1, say whether the following
symbols characterize an atomic orbital or not.
a) 1p b) 3f c) 4s d) 2d e) 5d
Question 4: (2 marks)
Which of the following molecules are polar? CHCl
3
, CCl
4
, H
2
O, CO
2
1. All the molecules.
2. CHCl
3
and CO
2.
3. CHCl
3
, CCl
4
and CO
2.
4. CHCl
3
and H
2
O.
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Question 5: (2 marks)
Consider the element with atomic number Z=30
1. How many s electrons has it? A) 11 B) 6 C) 4 D) 8
2. How many p electrons has it? A) 4 B) 12 C) 6 D) 8
3. How many d electrons has it? A) 10 B) 12 C) 2 D) 5
4. How many unpaid d electrons has it? A) 1 B) 0 C) 2 D) 4
Question 6: (2 marks)
Metallic character is associated with …………………………… and its periodic trend is:
1. Gain in electrons.
2. Loss in electrons.
3. Los in covalent electrons.
4. Increases across the periodic table from left to right and down the group, top to bottom.
5. Decreases across the periodic table from left to right and down the group, top to bottom.
6. Decreases across the periodic table from left to right and increases down the group.
Question 7: (2 marks)
A radius ratio of 0.414 – 0.732 suggests a coordination number of shape:
1. 6 / octahedral.
2. 4 / tetrahedral.
3. 6 or 4 / octahedral and tetrahedral.
4. 4 or 6 / square planar and octahedral.
Question 8: (2 marks)
According to the Hume-Rothery Rules, two elements will form an ideal solid solution if?
1. The electronegativity difference is close to zero.
2. The electronegativity difference is close to one.
3. One is electropositive and the other is electronegative.
4. If solute and solvent have similar valences.
5. The difference in the atomic size is >15%.
6. The two elements have different crystal structure.
Question 9: (2 marks)
In the hexagonal close packing of atoms
1. The radius ratio of r
+
/r
-
is >1.
2. The layers are stacked in the order ABCABC.
3. The coordination number of each atom is 12.
4. There is 1 octahedral hole for every 2 tetrahedral holes.
5. A tetrahedral hole is bound by 6 atoms.
6. An octahedral hole is bound by 8 atoms.
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SECTION B
Instructions: circle the letter corresponding to the best answer. Each question is a mark.
Question 10:
Using the Klechkowski Rule for writing electronic configurations, which is the correct electronic
configuration for Chromium, Cr (Z=24) AND Uranium, Ur (Z=92)?
a. 4d
4
4s
2
and 7s
2
5f
3
6d
1
b. 4s
2
3d
5
and 5f
3
6d
1
7s
2
c. 4s
1
3d
5
and 7s
2
5f
3
6d
1
d. 7s
2
5f
3
6d
1
and 4s
1
3d
5
Question 11:
Given that Fluorine, F has (
χ
F) = 3.98, and bond dissociation energies for F-F = 155kJ/mol., Br-Br =
193kJ/mol. and Br-F = 260kJ/mol. Calculate the electronegativity of bromine, using Pauling’s
electronegativity. a) 2.96 b) 3.04 c) 3.07 d) 3.16
Question 12:
The general chemical principle involved in the extraction of metals from their ores is by:
a. Reduction of the metal ions in the ores to metal ions.
b. Reduction of metal ions in the ores to metal atoms.
c. Purification of the ores.
d. Separation of earth from the ores froth floatation.
Question 13:
The geometry of the molecule COCl
2
with carbon as the central atom according to the VSEPR theory is:
a) AB
3
E
2
b) AB
3
c) AB
2
d) AB
2
E
Question 14:
According to Fajans’ Rule, arrange the following ionic compounds in order of increasing covalent
character: NaF, NaCl, NaBr, NaI.
a. NaF > NaCl > NaBr > NaI.
b. NaI > NaBr > NaCl > NaF.
c. NaF = NaCl > NaBr > NaI.
d. There is no covalent character in these ionic compounds.
Question 15:
Using the K
a
values for the following monoprotic acids, which is the strongest? K
a
(HClO
2
) = 1.12×10
-2
,
K
a
(CH
3
COOH) = 1.8×10
-5
, K
a
(HOCl) = 2.9×10
-8
, K
a
(HNO
2
) = 7.1×10
-4
.
a) HOCl b) HClO
2
c) CH
3
COOH d) HNO
2
Question 16:
Given that the K
a2
= 2×10
-2
for the diprotic acid H
2
SO
4
. Calculate the pH for this acid if it had an initial
concentration of 3.00×10
-3
M.
a) pH = -log(3.00×10
-3
) b) pH = 2.29 c) pH = -log(1.2×10
-2
) d) pH = -log(3×10
-3
+ 1.2×10
-2
)
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Question 17:
Which is the correct trend in electronegativity in the periodic table? Electronegativity:
a. Increases across a period and decrease down the group.
b. Increases across a period and increase down the group.
c. Decreases across a period and increase down the group.
d. Decreases across a period and decrease down the group.
Question 18:
Which among the propositions is very correct?
a. Beryllium an alkaline earth has the electronegativity is 1s
2
2s
1
.
b. Lithium with atomic number Z=3 has one principal shell.
c. Ca
2+
has the true noble gas configuration.
d. Fe
2+
has the true noble gas configuration.
Question 19:
Which is larger than the other, a tetrahedral or an octahedral hole?
a. A tetrahedral hole > octahedral hole.
b. A tetrahedral hole = octahedral hole.
c. An octahedral hole > tetrahedral hole.
d. The size varies from one close-packed structure to another.
Question 20:
Metal atoms are always arranged in the HCP or CCP model because:
a. The radius ratio of the atom is ≈ 1.
b. Of the metallic character.
c. Metals have free mobile electrons.
d. Metals are reducing agents.
Question 21:
In the ionic compound CaF
2
, the r
+
= 99pm and the r
-
= 136pm, which of these ions will fit in a close-
packed structure of the other?
a. Calcium ions will fit in a close-packing of Fluoride ions.
b. Fluoride ions will fit in a close-packing of Calcium ions.
c. Fluoride ions will fit into tetrahedral holes in the structure.
d. Calcium ions will fit into both tetrahedral and octahedral holes in the structure.
Question 22:
The r
+
/r
-
for Cd
2+/
I
-
is 0.454. What types of holes will Cd
2+
fill in a closed-packed structure of I
-
?
a. Tetrahedral holes.
b. Octahedral holes.
c. Half of the octahedral holes.
d. Half of the tetrahedral and half of the octahedral holes.
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