Topic 2

Question 1

Why is ethanol soluble in water?

Answer 1

Ethanol has an OH- group that allows it to form hydrogen bonds with water molecules

Question 2

Why is SO2 polar

Answer 2

Slightly negative charge on oxygen, while the sulphur atom has a slightly positive charge

Question 3

State and explain whether the electronegativity of Fluorine is greater than similar or less than Bromine

Hence or otherwise explain why hydrogen fluoride can form a hydrogen bond but hydrogen bromide cannot

Answer 3

Fluorine atom is more electronegative because it has less shielding and so the electrons are closer to the nucleus so there is a greater pull from the nucleus on these bonding electrons

HF has a greater dipole moment and is more polar than Br

Question 4

Propanone CH3COCH3 is a useful solvent for cleaning glassware in laboratories.
Why is propanone able to dissolve a wide range of substances

Answer 4

Propanone has both polar and non polar characteristics as it can form both London forces and hydrogen bonds

Question 5

Propanone can be used to remove both water and octane from glassware

For water and octane identify the strongest intermolecular forces formed with propanone and the feature of the propanone molecule involved

Answer 5

Water –> Hydrogen bonds with the oxygen of the carbonyl group
Octance –> London forces with methyl group

Question 6

What happens to electronegativity in a group in the Periodic Table

Answer 6

Decreases going down a group

Question 7

Would you expect a calcium ion to be bigger or smaller than a calcium atom.

Give two reasons to explain your answer

Answer 7

Smaller
It has one less sub shell of electrons and so therefore has less shielding
Ratio of protons and electrons has increased and therefore there are more protons than electrons and so a greater effective nuclear charge

Question 8

Explain why ionic compounds have relatively high melting temperatures?

Answer 8

Strong electrostatic forces between the ions

These ions are held in a giant lattice and so large amounts of energy are required to break apart ions

Question 9

Suggest why aqueous solutions of calcium chloride, CaCl2 (aq), and Barium chloride, BaCl2 (aq) of the same molar concentrations have different electrical conductivities

Answer 9

The cations of barium and calcium ions are different sizes

Question 10

Why does Hydrogen iodide not have hydrogen bonding despite having dipole-dipole interactions

Answer 10

It’s not a highly electronegative element (F, Cl, O, N)

Question 11

Why is the melting temperature of Mg higher than that of sodium

Answer 11

More energy is required to break the metallic bonds in Magnesium because Magnesium ions have a smaller ionic radius than Sodium so Magnesium is more closely packed
Mg2+ ions have a greater charge density than Na+ ions so Mg has more delocalised electrons than Sodium

Question 12

Define the term covalent bond

Answer 12

Occurs usually between non metals
The positively charged nuclei and negatively charged shared pairs of electrons between them are held together by strong forces of electrostatic attraction.
This can be held within a giant or simple covalent structure

Question 13

Which of these has a dative covalent bond

a) NH3
b) OH-
c) H2O
d) H3O+

Answer 13

d

Question 14

Which of these has the most polarized anion

a) Na2O
b) MgO
c) K2O
d) CaO

Answer 14

b

Question 15

In which series of compounds does covalent character increase when going from left to right

a) KI, KBr, KCl
b) NaI, KI, RbI
c) NaCl, MgCl2, AlCl3,
d) SO2, P4O10, SiO2

Answer 15

c

Question 16

Which of the following contains a dative covalent bond

a) N2
b) NH3
c) NH2-
d) NH4+

Answer 16

d

Question 17

The bonding in lithium iodide has some covalent character because

a) the lithium ion polarizes the iodide ion
b) the iodide ion polarizes the lithium ion
c) there is a very large difference in electronegativity between lithium and iodine
d) there is a very small difference in electronegativity between lithium and iodine

Answer 17

a

Question 18

What effect does infrared radiation have on the covalent bonds in water molecules in the atmosphere?

a) they are broken to form free radicals
b) they are broken into ions
c) the bonds vibrate more vigorously
d) there is no effect on the bonds

Answer 18

c

Question 19

In which series of compounds does the covalent character increase, going from left to right

a) NaCl, MgCl2, AlCl3, SiCl4
b) SiO2, Al2O3, MgO, Na2O
c) LiI, NaI, KI, RbI
d) KI, KBr, KCl, KF

Answer 19

a

Question 20

Fullerenes, graphite and diamond are all forms of carbon
Fullerenes dissolve in petrol, but diamond and graphite do not.
This is because

a) the bonds between the carbon atoms in fullerenes are weaker than in diamond or graphite
b) diamond and graphite are giant structures but fullerenes are molecular
c) there are delocalised electrons in diamond and graphite but not in fullerenes
d) there are covalent bonds in diamond and graphite but not in fullerenes

Answer 20

b

Question 21

Covalent bonding results from the strong electrostatic attractions between

a) instantaneous dipoles
b) electron clouds
c) electrons in the bonding pair
d) bonding pairs of electrons and nuclei

Answer 21

d

Question 22

What is the total number of electrons in the covalent bonds in a beryllium chloride molecule, BeCl2

a) 2
b) 4
c) 6
d) 8

Answer 22

b

Question 23

Which of the statements about carbon-carbon double bonds is false?

a) the two ends of a molecule cannot rotate relative to each other about the axis of the double bond
b) they are twice as strong as a c-c single bond
c) they have a higher electron density than a single bond
d) they consist of a sigma bond and a pi bond

Answer 23

b

Question 24

Buckminsterfullerene has the formula C60. It has similar bonding to the bonding in graphite

Which of the following is true

a) all the bond angles are 120
b) the melting temperature is higher than graphite
c) it has delocalised electrons
d) on complete combustion, it forms carbon dioxide and water

Answer 24

c

Question 25

Which of the following covalent bonds is the shortest

a) H-F
b) H-Cl
c) H- Br
d) H- I

Answer 25

a

Question 26

White phosphorus consists of

a) a giant structure of atoms
b) a giant structure of ions
c) small molecules
d) single atoms

Answer 26

c