Year 11 Chemistry Half-Yearly Exam Revision Solution
1. Write balanced equations for the reactions between each of the following, showing all states.
a) The combustion of ethane.
𝑪𝟐 𝑯𝟔 (𝒈) + 𝟕𝟐𝑶𝟐 (𝒈) → 𝟐𝑪𝑶𝟐 (𝒈) + 𝟑𝑯𝟐 𝑶 (𝒈) OR 𝟐𝑪𝟐 𝑯𝟔 (𝒈) + 𝟕𝑶𝟐 (𝒈) → 𝟒𝑪𝑶𝟐 (𝒈) + 𝟔𝑯𝟐 𝑶 (𝒈)
b) The neutralisation of nitric acid with aqueous sodium hydroxide.
𝑯𝑵𝑶𝟑 (𝒂𝒒) + 𝑵𝒂𝑶𝑯 (𝒂𝒒) → 𝑵𝒂𝑵𝑶𝟑 (𝒂𝒒) + 𝑯𝟐 𝑶 (𝒍)
c) The reaction between lithium and sulfuric acid.
𝟐𝑳𝒊 (𝒔) + 𝑯𝟐 𝑺𝑶𝟒 (𝒂𝒒) → 𝑳𝒊𝟐 𝑺𝑶𝟒 (𝒂𝒒) + 𝑯𝟐 (𝒈)
d) The reaction between calcium carbonate and hydrochloric acid.
𝟐𝑯𝑪𝒍 (𝒂𝒒) + 𝑪𝒂𝑪𝑶𝟑 (𝒔) → 𝑪𝒂𝑪𝒍𝟐 (𝒂𝒒) + 𝑯𝟐 𝑶 (𝒍) + 𝑪𝑶𝟐 (𝒈)
e) The reaction between sodium chloride and silver (I) nitrate.
𝑵𝒂𝑪𝒍 (𝒂𝒒) + 𝑨𝒈𝑵𝑶𝟑 (𝒂𝒒) → 𝑨𝒈𝑪𝒍 (𝒔) + 𝑵𝒂𝑵𝑶𝟑 (𝒂𝒒)
f) The electrolysis of water.
𝑯𝟐 𝑶 (𝒍) → 𝑯𝟐 (𝒈) + 𝟏𝟐𝑶𝟐 (𝒈)
𝟐𝑯𝟐 𝑶 (𝒍) → 𝟐𝑯𝟐 (𝒈) + 𝑶𝟐 (𝒈)
OR
2. Write balanced ionic equations for each of the following:
𝑶𝟐 + 𝟒𝒆− → 𝟐𝑶𝟐−
a) Oxygen molecules forming oxygen ions.
𝑴𝒈 → 𝑴𝒈𝟐+ + 𝟐𝒆−
b) Magnesium metal forming magnesium ions.
c) Copper (I) ions forming copper (II) ions.
d) Zinc ions forming zinc metal.
𝑪𝒖+ → 𝑪𝒖𝟐+ + 𝒆−
𝒁𝒏𝟐+ + 𝟐𝒆− → 𝒁𝒏
OR
𝒁𝒏𝟐+ + 𝟐𝒆− → 𝒁𝒏𝟎
3. The high proportion of which compounds in the lithosphere best explains the fact that oxygen and
silicon are the two most abundant elements in the lithosphere?
a) SiO2 and Al2O3
b) H2O and O2
c) MgO and diamond
d) sand and water
4. Wine can form crystals of calcium oxalate that fall to the bottom of the bottle and form a
sediment. When the wine is poured into a glass, the crystals can be suspended and enter the glass
and adversely affect the drinking experience. Which separation technique is traditionally used to
separate the calcium oxalate crystals from the wine? decanting
5. Why does gold usually exist in nature as a native metal, i.e. not a compound? It is very unreactive
6. Metals are malleable because metallic bonds are:
a) strong
b) weak
c) rigid
d) non-rigid
7. A mining company is considering building a silver mine. The company needs a minimum silver
content of 7% w/w in the ore to be profitable, so carry out a gravimetric analysis of a sample of ore.
Would the mine be profitable?
Mass of ore sample: 570g
%𝐀𝐠 𝐢𝐧 𝐀𝐠 𝟐 𝐒 =
Mass of argentite (Ag2S): 68.4g
𝟐 × 𝐌𝐀𝐠
𝟐 × 𝟏𝟎𝟕. 𝟖𝟕
× 𝟏𝟎𝟎% =
× 𝟏𝟎𝟎% = 𝟖𝟕. 𝟎𝟔%
𝟐 × 𝐌𝐀𝐠 + 𝐌𝐒
𝟐 × 𝟏𝟎𝟕. 𝟖𝟕 + 𝟑𝟐. 𝟎𝟔
𝐦𝐀𝐠
%𝐀𝐠 𝐢𝐧 𝐀𝐠 𝟐 𝐒 × 𝐦𝐀𝐠 𝟐𝐒
𝟖𝟕. 𝟎𝟔% × 𝟔𝟖. 𝟒𝐠
× 𝟏𝟎𝟎% =
× 𝟏𝟎𝟎% =
× 𝟏𝟎𝟎%
𝐦𝐨𝐫𝐞
𝐦𝐨𝐫𝐞
𝟓𝟕𝟎𝐠
= 𝟏𝟎. 𝟒𝟓% Therefore, the mine would be profitable.
%𝐀𝐠 𝐢𝐧 𝐨𝐫𝐞 =
8. An element that is brittle with a high melting point, low to moderate thermal and electrical
conductivity would most likely be classified as a:
a) metal
b) non-metal
c) semi-metal
d) compound
9. Draw Lewis dot diagrams for each of the following:
a) water molecule
b) oxide ion
c) argon atom
d) nitrogen molecule
10. Explain why CO2 is a gas at room temperature while SiO2 is a solid with a melting point of over
1600oC.
CO2 is covalent molecular. Subliming CO2 involves breaking weak intermolecular bonds,
not strong covalent bonds. SiO2 is covalent network. Melting SiO2 involves breaking strong
covalent bonds.
11. Why is it wrong to talk about the boiling point of vodka?
Vodka is a mixture of ethanol and
water. Only pure substances have a boiling point. Mixtures boil over a temperature range.
12. Why are metals good conductors of electricity?
charge carriers.
The "sea" of delocalised electrons are mobile
13. State two ways that the electrical conductivity of ionic compounds can be increased.
Melt or dissolve in a solvent to produce mobile charge carriers (positive and negative ions).
14. What do the following represent?
(𝑠), (𝑙), (𝑔) 𝑎𝑛𝑑 (𝑎𝑞)
(𝒔) = 𝒔𝒐𝒍𝒊𝒅, (𝒍) = 𝒍𝒊𝒒𝒖𝒊𝒅, (𝒈) = 𝒈𝒂𝒔, (𝒂𝒒) = 𝒂𝒒𝒖𝒆𝒐𝒖𝒔 (𝒅𝒊𝒔𝒔𝒐𝒍𝒗𝒆𝒅 𝒊𝒏 𝒘𝒂𝒕𝒆𝒓)
15. Where are metals found on the Periodic Table?
16. Where are non-metals found on the Periodic Table?
On the left-hand side.
On the right-hand side (except hydrogen).
17. Which group I element has very different properties from the other elements in group I?
H
18. Classify each of the following as chemical or physical changes and give a reason for your
classification.
a) Combustion of magnesium
b) Melting of water ice
Chemical change. Rearrangement of atoms.
Physical change. No rearrangement of atoms.
c) Thermal decomposition of copper (II) carbonate
Chemical change. Rearrangement of atoms.
19. What is the typical charge of ions formed from:
a) alkaline earth metals +2 Alkaline earth metals are in group II.
b) group III elements
c) halogens
+3
-1 Halogens are in group VII.
d) alkali metals
+1 Alkali metals are in group I.
e) group VI elements
f) noble gases
-2
Noble gases tend not to form ions.
g) group V elements
-3
20. Use the rule 2𝑛2 to determine the maximum number of electrons in the first 4 electron shells.
2
,
21. What does the formula CaCl2 mean?
8
,
18
,
32
Ca2+ ions and Cl– ions in the ratio of 1:2
22. Zinc oxide has the formula ZnO. What is the charge of the zinc ions in this compound?
+2
23. Why is the range of metals available to be used by humans greater now than 200 years ago?
Many metals were unavailable in the past because they are highly reactive and could not be
extracted from their ores with the technology available at the time. For example, the discovery of
aluminium needed to wait for the development of electricity.
24. Which elements are the following alloys made of:
a) steel
Fe and C
b) solder
Pb and Sn
c) bronze
Cu and Sn or Cu and As, P, Al, Mn or Si
d) brass
Cu and Zn
25. Complete the following table for each of the following isotopes.
Mass number
Atomic number
Number of electrons
Number of neutrons
Number of protons
Atomic weight of
element
Typical valency
Group number
Period number
Number of electron
shells
Number of electrons in
last shell
Electron configuration
Electrons in L shell
Carbon14
14
6
6
8
6
18
8O
tritium
18
8
8
10
8
3
1
1
2
1
Atoms formed from α
particles
4
2
2
2
2
4
4
2
2
2
2
1
1
1
2
2
4
2,4
4
48
Ca
126
Xe
48
20
20
28
20
126
54
54
72
54
0
8
1
2
2
4
0
8
5
1
1
4
5
2
1
8
2
8
2,6
6
1
0
2
0
2,8,8,2 2,8,18,18,8
8
8
26. Identify the type or types of bonding in each of the following substances.
Substance
Type(s) of
bonding
𝐻𝐶𝑙(𝑔)
Covalent
NaCl
Ionic
oxygen
NaOH
Aluminium
Diamond
Graphite
Covalent
Ionic
between
Na+ and
OH–.
Covalent
between
O and H.
Metallic
Covalent
network
Covalent
network
27. Explain why metals are malleable and good conductors of electricity.
The electrons are mobile charge carriers. The fact that the electrons are able to move means that
the bond between the positive metal ions and the sea of electrons is non-rigid.
28. True or false: A chemical change involves a rearrangement of particles.
True
29. The particle theory of matter says that:
All matter is made of particles.
Between the particles is empty space.
The particles are constantly moving.
30. Draw a container containing air. Show 8 nitrogen molecules, 2 oxygen molecules and 1 gaseous
water molecule (humidity).