SAMPLE MIDTERM TEST ANSWERS
Questions 1 to 20 are each worth 2 marks
1. According to VSEPR theory, what is the shape of CO 2 ?
(A) tetrahedral
(B) T-shaped
(C) angular
(D) linear
(E) triangular planar
OπCπO
AX 2 class
2. The correct formula for calcium perchlorate is
(A) Ca 2 (ClO 4
(B) Ca(ClO 3
3
(C) Ca 2 ClO 4
2
(D) Ca(ClO 4 ) 2
(E) CaClO 3
3. Which one of the following has …H ∵f π 0?
(A) Br 2 (l)
(B) LiF(s)
(C)
a compound
H 2 (g) is the standard state of H
C(diamond)
(D)
H 2 (l)
(E)
C(graphite) is the standard state of C
O 3 (g)
O 2 (g) is the standard state of O
4. Consider the following observed reaction,
Cl O ∯3 (aq) ρ I ∯ (aq) γ5
∯1
I O ∯3 (aq) ρ Cl ∯ (aq).
γ5
∯1
Which of the following statements is FALSE?
(A) ClO ∯3 acts as an oxidizing agent.
(B) 6 electrons are transfered from I ∯ to ClO ∯3 .
(C) ClO ∯3 is a stronger oxidizing agent than IO ∯3 .
(D) The chemical equation is balanced.
(E) Cl ∯ is a stronger reducing agent than I ∯ .
I ∯ and Cl ∯ are reducing agents of the left and right of the above reaction. The reaction proceeds
away from the stronger reducing agent.
5. Which one of the following atoms will never violate the octet rule when it forms compounds?
(A) Xe
period 5
(B) Cl
(C) N
period 3
(D)
period 2
P
(E)
period 3
I
period 5
6. Consider a mixture of CO(g) and O 2 (g) in a sealed 1 L container at 25 ∵ C and 3 atm pressure.
The mixture is heated until only CO 2 (g) remains. The product is then cooled back to 25 ∵ C. What
is the final pressure in the container?
(A) 1.0 atm
(B) 2.0 atm
(C) 3.0 atm
(D) 4.5 atm
(E) 6.0 atm
CO(g) ρ 1 O 2 (g) CO 2 (g)
2
If only CO 2 remains, then CO & O 2 must have been present in stoichiometric proportions (i.e.
1: 12 ) initially.
n O 2 π 12 n CO
&
n π n CO ρ n O 2 π 32 n CO
initially
pV π nRT
p init π n init RT/V π
3
2
n CO RT/V
p fin π n fin RT/V
&
n fin π n CO 2 ,fin π n CO,init π n CO
p fin π 23 p init π 2 atm.
[0.5 marks for (D) & 1 mark for (C)]
7. What volume of 0.5 M NaNH 2 will react with 126 g of pure nitric acid? The nitrogen containing
products are NH γ4 (aq) and NO ∯3 (aq).
(A) 1.0 L
(B) 2.0 L
(C) 4.0 L
(D) 8.0 L
(E) 0.5 L
NaNH 2 (aq) ρ 2 HNO 3 (aq) NaNO 3 (aq) ρ NH 4 NO 3 (aq)
126 g of pure nitric acid π 2.0 mol
We need 1.0 mol of NaNH 2 to consume 2.0 mol of HNO 3 .
1.0 mol
π 2.0 L
Vπ
0.5 mol/L
[0.5 marks for (A) & 1 mark for (C)]
8. Which one of the following statements is FALSE regarding atomic radii?
(A) Si is bigger than Cl.
(B) Si is bigger than C.
(C) Si is smaller than K.
(D) Si is bigger than F.
(E) Si is bigger than Na.
- 3rd period bigger than 2nd period Si † C & F)
- 3rd period smaller than 4th period Si ‐ K
- size decreases across a period Na † Si † Cl
9. Consider the following reactions:
…H π ∯…H vap ‐ 0
i) H 2 O(g) H 2 O(l)
ii) 2 NH 4 NO 3 (s) 2 N 2 (g) ρ 2 H 2 O(g) ρ O 2 (g)
explosive …H ‐ 0
iii) 2 Na(s) ρ 2 H 2 O(l) 2 NaOH(aq) ρ H 2 (g)
vigorous -recall that Na(s) melts on surface of water …H ‐ 0
Which one of the following statements is FALSE regarding these reactions?
(A) iii is exothermic.
(B) In i, the system does work on the surroundings.
…n gas π ∯1 volume decreases - work
is done on the system by the surroundings
(C) In ii, the system does work on the surroundings.
…n gas π 5
(D) i is exothermic.
(E) In iii, the system does work on the surroundings.
10. Which one electron configuration corresponds to an excited state of a halogen?
10
(A) [Ar] 3d 4s 2 4p 5
Br ground state
1
(D) [Ar] 4s
2
(B) [Ne] 3s 4p 4 4s 1
highly excited state of Cl
10 2
4
(C) [Ne] 4s
1
Na ground state
(E) [Ar] 3d 4s 4p
K ground state
Se ground state
[1 mark for (A)]
11. Which one of the following sets of reactants will produce a precipitate when the reactants are
combined?
(A) Cu(NO 3 ) 2 (aq) ρ NaOH(aq)
(B) HCl(aq) ρ NaOH(aq)
acid/base rxn - but no ppt
(C) HCl(aq) ρ Zn(s)
redox rxn with gas (H 2 ) formed - but no ppt
(D) NH 4 ClO 3 (aq) ρ AgNO 3 (aq)
(E) NaBr(aq) ρ Ba(ClO 4 ) 2 (aq)
[0.5 marks for (E) & 1.5 marks for (D)]
2∯
12. Which one of the following statements is FALSE regarding the sulfate (SO 2∯
4 ) and sulfite (SO 3 )
AX 4
anions?
AX 3 E
Lewis structure of SO 2∯
4 shows 4 equivalent S-O bonds - 2 double bonds & 2 single
bonds ave bond order π 1.5. Lewis structure of SO 2∯
3 shows 3 equivalent S-O bonds - 1 double
bond & 2 single bonds ave bond order π 1.333.
2∯
(A) The average S-O bond order is larger in SO 2∯
4 than in SO 3 .
(B) SO 2∯
4 is tetrahedral.
(C) SO 2∯
3 is triangular pyramidal.
True. SO 2∯
(D) Na 2 SO 3 (s) ρ H 2 O gives a weakly basic solution.
3 is the base conjugate to the
weak acid, HSO ∯3 .
False. All
(E) Na 2 SO 4 (aq) ρ NH 4 NO 3 (aq) produces a precipitate of (NH 4 ) 2 SO 4 (s).
ammonium salts are soluble.
13. The minimum frequency, in Hz (i.e. s ∯1 ), required to ionize H atoms in their first excited state
(i.e. n π 2) is given by
(A) 3.2910 15
(B) 2.1810 ∯18
(C) 8.2310 14
(D) 5.4510 ∯14
(E) 1.1510 15
14. How many resonance structures are required to describe the bonding in chlorate ion, ClO ∯3 ?
(A) 1
(B) 2
(C) 3
(D) 4
(E) more than 4
15. Which of the following combinations of H atom quantum numbers are allowed?
i) n π 3, ⇗ π 2, m π 1
iv) n π 2, ⇗ π 1, m π 2
ii) n π 1, ⇗ π 2, m π 0
v) n π 0, ⇗ π 0, m π 0
(A) i, ii and iii
(B) i, iii and v
(C) ii, iv and v
16. Which one of the following statements is FALSE?
iii) n π 2, ⇗ π 1, m π ∯
vi) n π 3, ⇗ π 2, m π ∯1
(D) i
(E) i, iii and vi
(A) The ground state electron configuration of Be has no unpaired electrons.
(B) The ground state electron configuration of Li has one unpaired electron.
(C) An H atom in its ground state (i.e. n π 1) cannot emit light.
(D) The ionization energy of Be is less than that of Li.
(E) The ionization energy of B is less than that of Be.
17. How much heat, in kJ, must be removed from 20.0 g of liquid H 2 O at 20 ∵ C to produce 20.0 g of
ice (i.e. solid H 2 O) at 0 ∵ C? The specific heat capacity of H 2 O(l) is 4.18 J g ∯1 K ∯1 and
…H fusion π 333 J g ∯1 for H 2 O(s).
(A) 6.66
(B) 1.67
(A) NH 3
(B) ClF 3
(C) 4.93
(D) 11.6
(E) 8.33
18. Which one of the following molecules is not polar (i.e. it does not have a net electric dipole)?
(C) BeF 2
(D) F 2 O
(E) HF
19. Which one of the following statements is FALSE concerning the equilibrium,
2 SO 2 (g) ρ O 2 (g) 2 SO 3 (g),
for which K c π 2.8 10 2 at 1000 K?
(A) K c π 3.6 10 ∯3 is the equilibrium constant for the reverse reaction.
(B) K c π 1.7 10 1 is the equilibrium constant for the reaction
SO 2 (g) ρ 1 O 2 (g) SO 3 (g).
2
(C) If 1 mole each of SO 2 , O 2 and SO 3 are combined in a 10 L flask at 1000 K, then the
reaction proceeds in the reverse direction until equilibrium is reached.
(D) If 0.01 mole each of SO 2 , O 2 and SO 3 are combined in a 10 L flask at 1000 K, then the
reaction proceeds in the reverse direction until equilibrium is reached.
(E) If the reaction quotient, Q c , is greater than K c , then the reaction proceeds in the reverse
direction until equilibrium is reached.
20. Which one of the following molecules has one nonbonding electron pair on the Cl atom?
(A) HCl
(B) ClF 3
(C) HClO
(D) HClO 3
Questions 21 to 30 are each worth 3 marks
(E) HClO 4
21. Which of the following statements are FALSE regarding the Lewis structures of IF γ2 and IF ∯2 ?
i) The average bond order is the same in these two ions.
ii) Only one of these ions has a net electric dipole moment.
iii) At least one of these ions has an unpaired electron.
iv) Both of these ions have an angular shape.
v) IF γ2 is isoelectronic with XeF 2 .
(A) i and iii
(B) ii and v
(C) iii, iv and v
(D) iii and iv
(E) iii and v
22. If 0.168 grams of a compound of B and H is burned in excess oxygen to give 0.422 grams of
B 2 O 3 , what is the empirical formula of the compound?
(A) BH 4
(B) BH 3
(C) BH 2
(D) BH
(E) B 2 H 3
23. Which one of the following statements is FALSE regarding the unbalanced reaction
FeCl 3 (aq) ρ NaSbCl 4 (aq) FeCl 2 (aq) ρ NaSbCl 6 (aq)?
(A) The Sb atom gains 2 electrons.
(B) Fe exists as Fe 2γ (aq) after completion of the reaction.
(C) The oxidizing agent is the aqueous ferric ion, Fe 3γ (aq).
(D) Two moles of FeCl 3 are required to completely consume one mole of NaSbCl 4 .
(E) Fe 3γ is a stronger oxidizing agent than SbCl ∯6 .
24. The Br-Br bond energy is 192 kJ mol ∯1 . What is the maximum wavelength (in meters) of light
capable of dissociating Br 2 molecules in the gas phase?
(A) 6.2310 ∯4
(B) 1.6110 ∯7
(C) 1.6110 7
25. Which one of the following statements is FALSE?
(D) 6.2310 ∯7
(E) 1.6110 ∯4
(A) The following atoms are ordered according to decreasing ionization energy: He † Ne † F †
B † Li.
(B) The following ions are ordered according to decreasing ionic radius: F ∯ † O 2∯ † N 3∯ .
(C) The following ions are ordered according to decreasing ionic radius: Rb γ † K γ † Ca 2γ †
Mg 2γ † Al 3γ .
(D) The electron affinity of Cl plus the ionization energy of Cl ∯ equals zero.
(E) The ionization energy of K γ is greater than the ionization energy of Ar.
26. Which of the following pairs of species have the same shape?
2∯
i) PO 3∯
3 and SO 3
∯
γ
iv) PF 4 and ICl 4
ii) NO ∯3 and SeO 2∯
iii) PF γ4 and ICl ∯4
3
∯
v) CCl 4 and BH 4
vi) CO 2 and IF γ2
(A) i, iv and v
(B) i, iii and v
(C) ii, iii and vi
27. Which one of the following statements are FALSE?
(A) The Cl-Cl bond energy π 2 …H ∵ ßCl(g) 1
2
(D) i and v
(E) ii and iii
Cl 2 (g)]
(B) …H ∵f [O(g)] † 0
(C) …H ∵ [2H 2 (g) ρ O 2 (g) 2H 2 O(g)] † …H ∵ [2H 2 (g) ρ O 2 (g) 2H 2 O(l)]
(D) …H ∵ [H 2 (g) ρ Br 2 (l) 2HBr(g)] † …H ∵ [H 2 (g) ρ Br 2 (g) 2HBr(g)]
(E) The nitrogen-nitrogen bond energy in N 2 is greater than that in N 2 H 4 .
28. Given the data,
…H ∵f [SrO(s)] π -592 kJ mol ∯1
…H ∵f [CO 2 (g)] π -394 kJ mol ∯1
∵
∵
∯1
…H f [C(g)] π 717 kJ mol
…H f [O(g)] π 279 kJ mol ∯1
…H ∵ [SrO(s) ρ CO 2 (g) SrCO 3 (s)] π -234 kJ mol ∯1 ,
which of the following statements are FALSE?
i) The average CπO bond energy in CO 2 π 835 kJ mol ∯1 .
ii) …H ∵f [SrCO 3 (s)] π -1420 kJ mol ∯1
iii) …H ∵f [SrO(g)] † -592 kJ mol ∯1
iv) The C⊟O bond energy in CO(g) π 996 kJ mol ∯1 ρ …H ∵f [CO(g)]
v) A system containing SrCO 3 (s) decomposing into SrO(s) and CO 2 (g) does work on the
surroundings.
(A) i, iii and v
(B) i, iv and v
(C) ii, iii and iv
(D) ii and iv
(E) ii
29. Which of the following statements are FALSE?
i) An AX 2 E 3 molecule has a linear shape.
ii) An AX 3 E 3 molecule has a triangular pyramidal shape.
iii) The average bond order in PO 3∯
4 is 5/4.
iv) ClF ∯2 is linear and its chlorine atom has 3 non-bonding electron pairs in the associated Lewis
structure.
v) ClF γ2 is angular and its chlorine atom has 2 non-bonding electron pairs in the associated Lewis
structure.
(A) i, iii and v
(B) i, ii and v
(C) ii and v
(D) ii
(E) iii and iv
30. Consider the equilibrium, 2 F 2 (g) ρ O 2 (g) 2 F 2 O(g), for which K p π 10 ∯6 and …H π 23 kJ
at some temperature, T. Which one of the following statements is FALSE?
(A) F 2 O, with a partial pressure of 10 ∯3 atm, will spontaneously decompose in the presence of F2
and O 2 with partial pressures of 0.5 atm and 2 atm, respectively.
(B) Increasing the temperature of an equilibrium mixture of these gases will cause the
decomposition of some F 2 O.
(C) Doubling the volume of a vessel initially containing an equilibrium mixture of these gases
will cause the decomposition of some F 2 O.
(D) A vessel initially contains a non-equilibrium mixture of these gases with Q p † K p . The
pressure in the vessel increases until equilibrium is reached.
(E) An equilibrium mixture has the following partial pressures (in atm): p F 2 O π 2 10 ∯3 ,
p F 2 π 2 and p O 2 π1.