Chemical Bonding
21 free MDCAT Chemistry MCQs on Chemical Bonding (PM&DC syllabus), each with the answer, an explanation and the textbook line it comes from. Tap to check, no sign-up.
Tap an answer to check it · 21 questions
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Question 1
Valence bond theory was developed in 1927 by:Show answer and explanation
Answer: A) Heitler and London
Hund and Mulliken: molecular orbital theory; Gillespie and Nyholm: VSEPR; Pauling and Slater: hybridization. Source: Chemistry 11 KPK (taleem360.com), p. 86.
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Question 2
The theory stating that electron pairs around a central atom stay as far apart as possible to minimize repulsion is:Show answer and explanation
Answer: B) VSEPR theory
It predicts shapes from the number of bond pairs and lone pairs. Source: Chemistry 11 KPK (taleem360.com), p. 77.
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Question 3
Writing two or more Lewis structures with identical positions of atoms for one compound is called:Show answer and explanation
Answer: C) Resonance
Benzene and ozone are examples; the real structure is the resonance hybrid. Source: Chemistry 11 KPK (taleem360.com), p. 84.
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Question 4
Half the difference between the numbers of electrons in bonding and antibonding molecular orbitals is the:Show answer and explanation
Answer: C) Bond order
H2: (2-0)/2 = 1; He2: (2-2)/2 = 0. Source: Chemistry 11 KPK (taleem360.com), p. 96.
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Question 5
On the basis of VSEPR theory, a molecule with three bond pairs and one lone pair on the central atom is:Show answer and explanation
Answer: C) Trigonal pyramidal
e.g. NH3; the lone pair is not counted in the shape. Source: Chemistry 11 KPK (taleem360.com), p. 82.
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Question 6
Which of the following is an example of a network solid?Show answer and explanation
Answer: D) Graphite
Diamond and graphite are covalent network solids; sugar, dry ice and iodine are molecular solids. Source: Chemistry 11 KPK (taleem360.com), p. 106.
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Question 7
Which one of the following molecules has zero dipole moment?Show answer and explanation
Answer: A) Carbon dioxide
In linear CO2 the two C=O bond dipoles cancel. Source: Chemistry 11 KPK (taleem360.com), p. 103.
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Question 8
Liquid oxygen is:Show answer and explanation
Answer: B) Paramagnetic
MOT shows two unpaired electrons in the antibonding pi* orbitals of O2. Source: Chemistry 11 KPK (taleem360.com), p. 98.
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Question 9
Which one of these molecules has the smallest bond angle?Show answer and explanation
Answer: D) Water
H2O 104.5 < NH3 107.5 < CH4 109.5 < BF3 120: two lone pairs compress the angle most. Source: Chemistry 11 KPK (taleem360.com), p. 82.
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Question 10
H2S has a net dipole moment while BeF2 has zero dipole moment, because:Show answer and explanation
Answer: A) H2S angular, BeF2 linear
In a linear molecule equal bond dipoles cancel; in an angular one they add up. Source: Chemistry 11 KPK (taleem360.com), p. 103.
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Question 11
According to VSEPR theory, the correct order of electron pair repulsion is:Show answer and explanation
Answer: B) Lone-lone > lone-bond > bond-bond
A lone pair occupies more space on the central atom than a bond pair. Source: Chemistry 11 KPK (taleem360.com), p. 78.
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Question 12
BeCl2, with two bond pairs and no lone pair on beryllium, has a shape that is:Show answer and explanation
Answer: C) Linear
The two bond pairs lie on opposite sides at 180. Source: Chemistry 11 KPK (taleem360.com), p. 79.
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Question 13
SnCl2, with two bond pairs and one lone pair on tin, has a shape that is:Show answer and explanation
Answer: D) Angular
The lone pair takes one corner of the triangle, reducing the angle below 120 (about 95). Source: Chemistry 11 KPK (taleem360.com), p. 80.
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Question 14
The bond angle in NH3 is less than the tetrahedral angle because:Show answer and explanation
Answer: B) Lone pair repulsion is greater
Lone pair-bond pair repulsion exceeds bond pair-bond pair repulsion, pushing the N-H bonds closer. Source: Chemistry 11 KPK (taleem360.com), p. 82.
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Question 15
An ethene (C2H4) molecule contains:Show answer and explanation
Answer: C) Five sigma, one pi bond
Four C-H and one C-C sigma bond plus one pi bond; ethyne has three sigma and two pi. Source: Chemistry 11 KPK (taleem360.com), p. 92.
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Question 16
A pi bond is weaker than a sigma bond because:Show answer and explanation
Answer: B) Its overlap is not maximum
Sidewise overlap is less effective; a pi bond cannot exist without a sigma bond. Source: Chemistry 11 KPK (taleem360.com), p. 88.
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Question 17
The He2 molecule does not exist because its bond order is:Show answer and explanation
Answer: C) Zero
Two electrons in bonding and two in antibonding orbitals: (2-2)/2 = 0. Source: Chemistry 11 KPK (taleem360.com), p. 98.
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Question 18
Most ionic compounds dissolve in water but not in benzene because water is:Show answer and explanation
Answer: C) Polar
Like dissolves like. Source: Chemistry 11 KPK (taleem360.com), p. 104.
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Question 19
Covalent bonds are directional because they are formed by:Show answer and explanation
Answer: D) Overlap of atomic orbitals
Orbitals have definite directions, so molecules have definite geometry (e.g. 109.5 in CH4). Source: Chemistry 11 KPK (taleem360.com), p. 105.
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Question 20
Formic acid melts at 8.4 C but propane, of similar molar mass, at -190 C because formic acid has:Show answer and explanation
Answer: B) Hydrogen bonding and dipole forces
Polar molecules with permanent dipoles and hydrogen bonds melt at higher temperatures. Source: Chemistry 11 KPK (taleem360.com), p. 106.
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Question 21
Valence bond theory fails to explain:Show answer and explanation
Answer: C) Paramagnetism of oxygen
It also fails for coordinate bonds and odd-electron species such as H2+; MOT explains O2 paramagnetism. Source: Chemistry 11 KPK (taleem360.com), p. 94.
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