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PAPER 2 EXAM QUESTIONS
04 NOVEMBER 2014
Lesson Description
In this lesson we:



Revise concepts of the atom, chemical formulae and equations.
Solve chemical calculations using mole ratios.
Practise answering exam questions.
Challenge Question
Calculate the number of protons in a sample of 1.74 kg of lead (Pb).
Test Yourself
Question 1
(DBE Grade 10 2006)
Choose an item from COLUMN B that best matches a description/item in COLUMN A. Each item in
COLUMN B may be used only ONCE.
Column A
Column B
1.1
Potassium chloride crystals
A
heterogeneous mixture
1.2
A good conductor of electricity
B
homogeneous mixture
1.3
A non-metal element
C
silicon
1.4
Sugar dissolved in water
D
Density
1.5
Blood
E
sulphur
1.6
Increasing conductivity with increase in
temperature
F
compound
1.7
Mass per volume
G
Cu
Question 2
The chemical formula of potassium sulphate is…
A
KSO4
B
PSO4
C
PSO2
D
K2SO4
Question 3
(DBE Grade 10 2006)
+
When an atom X of an element in Group 1 reacts to become X , the …
A
mass number of X increases.
B
atomic number of X decreases.
C
charge of the nucleus increases.
D
number of filled energy levels decreases.
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Question 4
The sodium ion has the same electron configuration as…
A
argon
B
chloride ion
C
fluoride ion
D
helium
Exam Questions
Question 1
Uranium is a reactive element. Two of its isotopes are Uranium-238 and Uranium-235.
A sample of uranium is found to have 99.3% Uranium 238 and 0.7% Uranium 235.
a. Define the terms:
Element
Isotope
b. Write the standard notation for both isotopes.
c. Calculate the relative atomic mass of the sample of uranium.
Question 2
Calcium chloride can be decomposed through the process of electrolysis, by passing an electric
current through an aqueous solution of calcium chloride. Solid calcium and gaseous chlorine are
formed.
a.
b.
c.
d.
e.
f.
State what is meant by the term aqueous.
Write down the formulae of the ions present in this solution.
Could a current pass through a sample of solid calcium chloride? Explain your answer
fully.
Suggest two factors which could increase the conductivity of this electrolyte.
Write an equation for the decomposition of calcium chloride. Include state symbols.
Name the law that a balanced equation represents.
Question 3
Ammonium carbonate decomposes according to the following equation.
Ammonium carbonate → ammonia + water + carbon dioxide
a.
b.
c.
d.
Write formulae for and balance the word equation.
Determine the molar mass of ammonium carbonate.
Calculate the number of moles if 336 g of ammonium carbonate react.
What volume of ammonia gas is released through this reaction at STP?
Links

www.everythingscience.co.za
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Answers
Challenge Question
8.41 mols of Pb.
24
5.06 x 10 atoms of lead
26
4.15 x 10 protons
Test Yourself
1.
1.1
1.2
1.3
1.4
1.5
1.6
1.7
F
G
E
B
A
C
D
2. D
3. D
4. C
Exam Questions
Question 1
a. Element: a substance that cannot be broken down into other substances through chemical
means.
Isotopes of an element have the same number of protons, but a different number of neutrons
b. Standard notation both isotopes – drawing.
c. Relative atomic mass of the sample of uranium.
238.98 amu
Question 2
a.
b.
c.
d.
e.
f.
Dissolved in water.
2+
Ca and Cl
No, because in an ionic solid the ions are held in a crystal lattice – no movement of charge.
Higher temperature, stronger concentration of ions.
CaCl2 (aq)  Ca (s) + Cl2 (g)
Conservation of matter.
Question 3
a.
(NH4)2CO3  2NH3 + H2O + CO2 
-1
b. Mm = 96 g.mol
c.
3.5 mols
d.
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