1.	C
[1]

2.	A
[1]

3.	D
[1]

4.	A
[1]

5.	C
[1]

6.	(i)	calcium ionic charge is twice/greater than the potassium ionic charge /
calcium has more delocalized electrons than potassium;
greater attraction of delocalized electrons and Ca^2+ / less attraction
between the delocalized electrons and K^+;	2
Do not accept calcium ion has a 2^+ without comparison to K^+.
 
(ii)	Na_2O ionic/(stronger electrostatic) attractions between Na^+ and O^2–;
SO_3 has (weak) intermolecular/van der Waals’/London/dispersion/
dipole-dipole attractions;
intermolecular/van der Waals’/London/dispersion/dipole-dipole forces
are weaker/more easily broken than (strong) ionic bonds / ionic bonds
are stronger/harder to break than intermolecular bond/van der
Waals’/London/dispersion/dipole-dipole forces;	3
[5]

7.	Award [2 max] for three of the following features:
	Bonding
	Graphite and C_60 fullerene: covalent bonds and van der Waals’/London/
dispersion forces;
Diamond: covalent bonds (and van der Waals’/London/dispersion forces);
	Delocalized electrons
	Graphite and C_60 fullerene: delocalized electrons;
Diamond: no delocalized electrons;
	Structure
	Diamond: network/giant structure / macromolecular / three-dimensional
structure and Graphite: layered structure / two-dimensional
structure / planar;
C_60 fullerene: consists of molecules / spheres made of atoms arranged in
hexagons/pentagons;
	Bond angles
	Graphite: 120° and Diamond: 109°;
C_60 fullerene: bond angles between 109–120°;
Allow Graphite: sp^2 and Diamond: sp^3.
Allow C_60 fullerene: sp^2 and sp^3.
	Number of atoms each carbon is bonded to
	Graphite and C_60 fullerene: each C atom attached to 3 others;
Diamond: each C atom attached to 4 atoms / tetrahedral
arrangement of C (atoms);	6 max
[6]

8.	;
linear and 180°;	2
Accept crosses, lines or dots as electron pairs.
[2]

9.	network/giant structure / macromolecular;
each Si atom bonded covalently to 4 oxygen atoms and each O
atom bonded covalently to 2 Si atoms / single covalent bonds;	2
Award [1 max] for answers such as network-covalent, giant-covalent or
macromolecular-covalent.
Both M1 and M2 can be scored by a suitable diagram.
[2]

10.	Silicon dioxide: strong/covalent bonds in network/giant structure/macromolecule;
Carbon dioxide: weak/van der Waals’/dispersion/London forces between molecules;	2
[2]

11.	triple (covalent) bond;
one electron pair donated by oxygen to carbon atom / dative (covalent)/
coordinate (covalent) bond;	2
Award [1 max] for representation of C≡O.
Award [2] if CO shown with dative covalent bond.
[2]

12.	A
[1]

13.	(a)	vapour pressure ethoxyethane (81 × 10^3 Pa) > vapour pressure
benzene (16 × 10^3 Pa) > vapour pressure water (4 × 10^3 Pa);
If three correct vapour pressure values related to each substance
are stated alone award M1.
Allow range of 80–85 × 10^3 Pa, 14–18 × 10^3 Pa and 3–7 × 10^3 Pa.
Do not award mark for comparisons of just two substances.
	water has hydrogen bonding;
benzene has van der Waals’/London/dispersion forces;
ethoxyethane has dipole–dipole forces (and van der Waals’/London/
dispersion) but they are weaker than benzene;	4
 
(b)	81 °C;	1
Allow 80–82 °C.
[5]

14.	Molten sodium oxide: conducts because of free moving/mobile ions in
molten state;
Sulfur trioxide: doesn’t conduct because no free moving/mobile charged
particles/it has neutral molecules;	2
Award [1 max] for stating molten sodium oxide conducts but sulfur
trioxide doesn’t.
Do not award M2 for just “sulfur trioxide does not conduct because
it is molecular”.
[2]

15.	B
[1]

16.	C
[1]

17.	B
[1]

18.	D
[1]

19.	C
[1]

20.	(a)	(i)	+3;	1
Do not accept 3, 3+ or the use of Roman numerals.
 
(ii)	+5 / –3;	1
Penalize incorrect format only if not penalized in (a)(i).
 
(b)	(i)	Sb_2S_3 + 4O_2 → Sb_2SO_3 + 2SO_2 / 2Sb_2S_3 + 9O_2 → 2Sb_2O_3 + 6SO_2;
2Sb_2O_3 + 3C → 4Sb + 3CO_2 / Sb_2O_3 + 3C → 2Sb + 3CO;	2
Ignore state symbols.
 
(ii)	the SO_2 causes acid rain / OWTTE;
the CO_2 is a greenhouse gas/causes global warming / OWTTE;
CO is a poisonous gas / OWTTE;	2 max
[6]

21.	methoxymethane is very weakly polar
weak van der Waals’/dipole-dipole forces exist between methoxymethane
molecules;
Accept alternatives to van der Waals’ such as London and dispersion forces.
	ethanol contains a hydrogen atom bonded directly to an electronegative
oxygen atom / hydrogen bonding can occur between two ethanol
molecules / intermolecular hydrogen bonding in ethanol;
the forces of attraction between molecules are stronger in ethanol than
in methoxymethane / hydrogen bonding stronger than van der Waals’/
dipole-dipole attractions;	3 max
Award [2 max] if covalent bonds breaking during boiling is
mentioned in the answer.
Penalize only once if no reference given to intermolecular nature
of hydrogen bonding or van der Waal is missing.
[3]

22.	(i)

Accept any combination of dots/crosses and lines to represent
electron pairs.
	(trigonal/triangular) pyramid;
Allow 3D representation using wedges and dotted bonds of
trigonal pyramidal molecule.
107°;	3
	Accept any angle between 105º and 108.5º.
No ECF for shape based on incorrect Lewis structure.
 
(ii)

Charge needed for mark.
	tetrahedral;
Allow a 3D representation using wedges and dotted bonds
of tetrahedral molecule.
	109.5°/109°/109° 28';	3
No ECF for shape based on incorrect Lewis structure.
[5]

23.	D
[1]

24.	A
[1]

25.	D
[1]

26.	D
[1]

27.	A
[1]

28.	A
[1]

29.	B
[1]

30.	(i)

Accept lines, dots or crosses for electron pairs.
Lone pairs required on chlorine.
	(approximately)120°;
Accept any bond angle in the range 113–120°.	2

(ii)

Brackets not required for mark.
Allow correct condensed structural formula.
Continuation bonds from each carbon are required.
Cl atoms can be above or below carbon spine or alternating
above and below.	1
 
(iii)	plastics are cheap/versatile/a large industry / plastics have
many uses / OWTTE;
plastics are not biodegradeable / plastics take up large amounts of space in
landfill / pollution caused by burning of plastics / OWTTE;
Do not accept plastics cause litter.
Allow plastics don’t decompose quickly / OWTTE.	2
[5]

31.	A
[1]

32.	D
[1]

33.	B
[1]

34.	A
[1]

35.	B
[1]

36.	D
[1]

37.	(a)	N_2H_4(g) + 2F_2(g) → N_2(g) + 4HF(g)
Award [1] for reactants and products.
Award [1] if this equation is correctly balanced.
Ignore state symbols.	2
 
(b)	Hydrazine:

	Nitrogen:
;
Accept lines, dots and crosses to show electron pairs.
Penalize missing lone pairs once only.	2
 
(c)	ΣBE (bonds broken) = (4 × 391) + 158 + 2(158) / 2038(kJ);
ΣBE (bonds formed) = (945) + 4(568) / 3217 (kJ);
∆H~~^O~~ = 2038 – 3217 = –1179 (kJ);
Award [3] for correct final answer.
Award [2] for (+)1179 (kJ).	3
 
(d)	(N_2H_4 / F_2) better rocket fuel;
ECF: answer must be consistent with equation in (a) and ∆H in (c).
	5 vol/mol (g) > 3 vol/mol (g) / more moles/greater amount of gas produced;
∆H~~^O~~ (N_2H_4 / F_2) > ∆H~~^O~~ (N_2H_4 / O_2) (per mole) / (N_2H_4 / F_2) reaction more
exothermic;	2 max
[9]

38.	(i)	energy/enthalpy change/required/needed to remove/knock out an electron
(to form +1 /uni-positive/ M^+1 ion);
in the gaseous state;
Award [1] for M(g) → M^+(g) + e^–.
Award [2] for M(g) → M^+(g) + e^– with reference to energy/enthalpy change.	2
 
(ii)	increasing number of protons/atomic number/Z/nuclear charge;
atomic radii/size decreases / same shell/energy level / similar shielding/
screening (from inner electrons);
No mark for shielding/screening or shielding/screening increases.	2
 
(iii)	Na: delocalized electrons / mobile sea of electrons / sea of electrons
free to move;
No mark for just “mobile electrons”.
	P: atoms covalently bonded / no free/mobile/delocalized electrons;	2
[6]

39.	B
[1]

40.	D
[1]

41.	C
[1]

42.	D
[1]

43.	A
[1]

44.	metallic (bonding);
positive ions/cations and delocalized/sea of electrons;
electrostatic attraction between the two;
Award [2 max] for description of bonding
	Conductivity:
electrons delocalized/free to move;
	Malleability:
atoms/ions/cations can move without breaking bonds / atoms/ions/
cations can slide past each other;	4
[4]

45.	(a)	(i)

Accept ×’s, dots or lines for electron pairs.	2
 
(ii)	H–C–H:
any angle between 118° and 122°;
due to three negative charge centres/electron domains/electron pairs;
	H–N–H:
any angle between 104° and 108°;
due to four negative charge centres/electron domains/electron pairs;
extra repulsion due to lone electron pairs;
Do not allow ECF for wrong Lewis structures.	5
 
(b)	(i)	(relative) measure of an atoms attraction for electrons;
in a covalent bond / shared pair;	2
 
(ii)	C–H is less polar as C is less electronegative / N–H bond is more polar
as N is more electronegative / difference in electronegativity is greater
for N-H than C-H;	1
 
(iii)	bond polarities cancel in C_2H_4 / OWTTE;	1
 
(c)	weaker van der Waals’/London/dispersion/intermolecular forces in ethene;
stronger (intermolecular) hydrogen bonding in hydrazine;
If no comparison between strengths then [1 max].	2
[13]

46.	(i)	acid-base/neutralization;	1
 
(ii)	109° /109.5°;	1
[2]

47.	D
[1]

48.	C
[1]

49.	D
[1]

50.	A
[1]

51.	(i)

All outer electron pairs must be shown for mark in each case.
Accept electrons shown as all x rather than • and x.	3
 
(ii)	CO < CO_2 < CH_3OH;
triple bonds are shorter than double bonds which are shorter than single
bonds / the more pairs of electrons that are shared the stronger the
attracting so the shorter the bond / OWTTE;
The order must be correct to gain the second marking point
unless ECF from (a).	2
[5]

52.	(i)	(CO_2)	linear;
	180°;	2
 
(ii)	(CO_3^2–)	trigonal planar/triangular planar;
	120°;	2
 
(iii)	(BF_4^–)	tetrahedral;
	109.5° / 109° / 109° 28’;	2
[6]

53.	D
[1]

54.	D
[1]

55.	D
[1]

56.	B
[1]

57.	C
[1]

58.	C
[1]

59.	(i)	atoms of the same element with the same atomic number/Z/same number
of protons, but different mass numbers/A/different number of neutrons;	1

(ii)	(0.9223 × 28) + (0.0468 × 29) + (0.0309 × 30);
28.1/28.11;
Working must be shown to get [2], do not accept 28.09 on its own (given
in the data booklet).	2
 
(iii)	Silicon dioxide
single covalent (bonds);
network/giant covalent/macromolecular / repeating tetrahedral units;
	Carbon dioxide
double covalent (bonds);
(simple / discrete) molecular;
Marks may be obtained from suitable structural representations
of SiO_2 and CO_2.	4
[7]

60.	

Allow crosses or dots for lone-pair.
	trigonal/triangular pyramidal;
(~)107° / less than 109.5°;
Do not allow ECF.
	LP-BP repulsion > BP-BP repulsion / one lone pair and three bond pairs /
lone pairs/non-bonding pairs repel more than bonding-pairs;
Do not accept repulsion between atoms.	4
[4]

61.	boiling points increase going down the group (from PH_3 to AsH_3 to SbH_3);
M_r/number of electrons/molecular size increases down the group;
Accept electron cloud increases down the group for the second marking point.
	greater dispersion/London/van der Waals’ forces;
	NH_3/ammonia has a higher boiling point than expected due to the hydrogen
bonding between the molecules;
Do not accept hydrogen bonding alone.	4
[4]

62.	CO:

Award [1] for showing the net dipole moment, or explaining it in words
(unsymmetrical distribution of charge).
	NO_2:

Award [1] for correct representation of the bent shape and [1] for showing the
net dipole moment, or explaining it in words (unsymmetrical distribution of charge).
	CO_2:

Award [1] for correct representation of the linear shape and [1] for showing the
two equal but opposite dipoles or explaining it in words (symmetrical
distribution of charge).
	For all three molecules, allow either arrow or arrow with bar for
representation of dipole moment.
Allow correct partial charges instead of the representation of the
vector dipole moment.
Ignore incorrect bonds.
Lone pairs not needed.	5
[5]

63.	Structure:
network/giant lattice / macromolecular / repeating tetrahedral units;
Bonding:
(single) covalent (bonds);
It is not necessary to identify which part refers to structure and bonding specifically.	2
[2]

64.	B
[1]

65.	C
[1]

66.	C
[1]

67.	B
[1]

68.	C
[1]

69.	
| PF_3 | SF_2 | SiF_4

Lewis
structure

1 lone pair on P required for the mark

2 lone pairs on S required for the mark

Name of
shape

trigonal/triangular pyramidal;

bent/angular/V shaped;

tetrahedral/tetrahedron;

	Penalize missing lone pairs on fluorine atoms once in correct structures only.
For Lewis structures candidates are not expected to draw exact shapes of molecules.
Do not allow ECF for wrong Lewis structures.
Accept dots or crosses instead of lines.	6
[6]

70.	D
[1]

71.	B
[1]

72.	B
[1]

73.	B
[1]

74.	D
[1]

75.	A
[1]

76.	B
[1]

77.	B
[1]

78.	(i)	Find number of electron pairs/charge centres in (valence shell of)
central atom;
electron pairs/charge centres (in valence shell) of central atom repel
each other;
	Any one of the following:
to positions of minimum energy/repulsion / maximum stability;
pairs forming a double or triple bond act as a single bond;
non-bonding pairs repel more than bonding pairs / OWTTE;	3 max
Do not accept repulsion between bonds or atoms.

(ii)		6

Species

Lewis (electron-dot)
structure

Shape

Bond angle(s)

H_3O^+ | | Trigonal/triangular pyramidal; | Allow values in the range 106° to 109.5°;
C_2H_4 | | Trigonal/triangular planar; | Allow values of approximately 120°;
Accept crosses and dots for electrons in Lewis structures also.
As the Lewis structures were asked for, and not 3D representations, do not penalize incorrectly drawn geometries.
Do not accept structure of hydronium cation without lone pair on oxygen.
No penalty for missing charge.
 
(iii)	H_3O^+: is polar and explanation either using a diagram or in words,
involving the net dipole moment;
e.g. the three individual O-H bond dipole moments add as vectors to give a net dipole moment.
	C_2H_4: is non-polar and explanation either using a diagram or in words,
involving no net dipole moment;	2
e.g. the vector sum of the individual bond dipole moments is zero.
For simple answers such as bond polarities do not cancel for H_3O^+ and do cancel for C_2H_4, Award [1], only for the last two marking points.
 
(iv)	O-H is most polar;
O-H has greatest difference between electronegativities / calculation
showing values of 1.4, 0.5 and 0.9 respectively;	2
[13]

79.	BF_3, N_2O, P_4O_6 and CBr_4;
Non-metals only / small difference in electronegativity values of the elements;	2
[2]

80.	(i)	3
Allotrope | Structure
Diamond | 3D array/network involving tetrahedral carbons / each carbon atom joined to four others;
Graphite | layer structure involving trigonal (triangular) planar carbons / with each carbon atom joined to three others / with hexagonal (six-membered) rings of carbon atoms;

C_60 fullerene

truncated icosahedrons;
Accept carbon atoms form a “ball” with 32 faces, of which 12 are pentagons and 20 are hexagons, exactly like a soccer ball. Do not accept soccer ball alone.

(ii)	Diamond: covalent bonds (only);
Graphite: covalent bonds and the separated layers held together by
(weak) London/van der Waals’/dispersion forces;	2
[5]

81.	Electrical conductivity:
Bonding electrons are delocalized;
Current flow occurs without displacement of atoms within the metal /
able to flow within the metal;
	Malleability:
Can be hammered into thin sheets;
atoms capable of slipping with respect to one another;	4
[4]

IB Questionbank Chemistry