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Chemistry
WAEC / WASSCE 2020
Particulate Nature of Matter, Laws & Formulae
Solution
A balanced chemical equation is based on the law of?
A
Periodicity
B
Constant composition
C
Multiple proportion
D
Conservation of mass
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The law of conservation of mass is important because it allows us to predict the amount of product formed in a chemical reaction, as well as the amount of consumed reactant.
Source: Myschool Past Questions Archive (Record #58846)
Chemistry
WAEC / WASSCE 2020
Periodic Table & Periodicity
Solution
Which of the following pairs of elements has the greatest difference in electronegativity?
A
Na and F
B
Na and CI
C
Na and Br
D
Na and I
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
- sodium has an electro negativity of 0.93
- Hence; sodium and flourine have the highest difference.
Fluorine
4.0
Chlorine
3.0
Bromine
2.8
Iodine
2.5
Source: Myschool Past Questions Archive (Record #58852)
Chemistry
WAEC / WASSCE 2020
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
A factor that is considered most important when siting a chemical industry is?
A
nearness to other industrial establishments
B
nearness to raw materials
C
favourable climate conditions
D
availability of storage facilities
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #58856)
Chemistry
WAEC / WASSCE 2020
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
The boiling point of pentane is higher than that of propane because?
A
carbon-carbon single bonds are stronger than carbon-hydrogen bonds.
B
Pentane has more covalent bonds to break
C
Pentane does not burn easily as
propane
D
The intermolecular forces in pentane are stronger than those of propane
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The boiling points of alkanes increase with increasing number of carbons. This is because the intermolecular attractive forces, although individually weak, become cumulatively more significant as the number of atoms and electrons in the molecule increases.
Source: Myschool Past Questions Archive (Record #58862)
Chemistry
WAEC / WASSCE 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which of the following solids would not decompose on heating?
A
Ammonium chloride
B
Lead (i) trioxonitrate (V)
C
Potassium trioxocarbonate (IV)
D
Sodium hydrogen trioxocarbonate (IV)
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
trioxoxcarbonates (iv) of Na & K are stable to heat
Source: Myschool Past Questions Archive (Record #58874)
Chemistry
WAEC / WASSCE 2020
Chemical Bonding & Intermolecular Forces
Solution
The following molecules have double covalent bonds between two atoms except?
A
oxygen
B
carbon (IV)oxide
C
ethene
D
water
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
In the case of water, hydrogen bonds form between neighboring hydrogen and oxygen atoms of adjacent water molecules. The attraction between individual water molecules creates a bond known as a hydrogen bond.
Source: Myschool Past Questions Archive (Record #58881)
Chemistry
WAEC / WASSCE 2020
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
The type of isomerism exhibited by cis and trans isomers is?
A
positional
B
geometrical
C
functional
D
optical
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
- Cis–trans isomerism, also known as geometric isomerism or configurational isomerism arises when atoms or groups are arranged differently in space due to restricted rotation of a bond or bonds in a molecule.
Source: Myschool Past Questions Archive (Record #58884)
Chemistry
WAEC / WASSCE 2020
Stoichiometry, Mole Concept & Volumetric Analysis
An alkanol containing 60% carbon by mass would have a molecular formula [H=1.0. C-12.0, O= 16.0]
A
CH\(_3\)OH
B
C\(_2\)H\(_5\)OH
C
C\(_3\)H\(_7\)OH
D
C\(_4\)H\(_9\)OH
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #58896)
Chemistry
WAEC / WASSCE 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following compounds would release hydrogen when reacted with sodium metal?
I. CH\(_3\)COOH
II. CH\(_3\)CH\(_2\)OH
III. CH\(_3\)COOCH\(_3\)
A
I only
B
I and II only
C
Il and IIl only
D
I and Ill only
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option B.
Source: Myschool Past Questions Archive (Record #58911)
Chemistry
WAEC / WASSCE 2020
Oxidation, Reduction & Redox Reactions
Solution
Which of the following substances is not a reducing agent?
A
C
B
CO
C
O\(_2\)
D
H\(_2\)
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
- A reducing agent is oxidized, because it loses electrons in the redox reaction.
- Elemental oxygen is a strong oxidizing agent.
Source: Myschool Past Questions Archive (Record #58921)
Chemistry
WAEC / WASSCE 2020
Reaction Rates & Chemical Equilibrium
Solution
Which of the following statements is correet for a reaction at equilibrium?
A
All reactions cease to occur
B
The eaction has gone to completion
C
The rates of the forward and backward reactions are equal
D
The amount of product equals the amount of reactants
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
In a chemical reaction, chemical equilibrium is the state in which the forward reaction rate and the reverse reaction rate are equal. The result of this equilibrium is that the concentrations of the reactants and the products do not change.
Source: Myschool Past Questions Archive (Record #59000)
Chemistry
WAEC / WASSCE 2020
Acids, Bases, pH & Salts
Solution
Which of the following reactions are always exothermic? 1. Neutralization Il. Decomposition III. Combustion
A
I and II only
B
I and III only
C
II and IIl only
D
I, II and III
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
LIST OF EXOTHERMIC REACTIONS
any combustion reaction.
a neutralization reaction.
rusting of iron (rust steel wool with vinegar)
the thermit reaction.
reaction between water and calcium chloride.
reaction between sodium sulfite and bleach (dilute sodium hypochlorite)
reaction between potassium permanganate and glycerol.
Source: Myschool Past Questions Archive (Record #59001)
Chemistry
WAEC / WASSCE 2020
Chemical Energetics & Thermochemistry
Solution
Which of the following standard conditions is not correct about energy changes?
A
Standard temperature is 298K
B
B. Standard pressure is 1 atm
C
Concentration of solution must be 1 mol/dm\(^3\)
D
ΔH at 298 K is the activation energy
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
the standard conditions of 1 atm pressure and 298K.
Source: Myschool Past Questions Archive (Record #59002)
Chemistry
WAEC / WASSCE 2020
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
f 5.0 cm\(^-3\) of 0.200 mol dm(^-3\) Na\(_2\)CO\(_3\) was diluted to 250cm(^-3\) solution, what would be the concentration of the resulting solution?
A
0.004 mol dm(^-3\)
B
0.020 mol dm(^-3\)
C
0.200 mol dm(^-3\)
D
0.400 mol dm(^-3\)
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
=
initial molarity
=
initial volume in liters
=
final molarity
=
final volume in liters
0.200 X 5.00 = M\(_2\) X 250
M\(_2\) = 1 / 250
M\(_2\) = 0.004 mol dm(^-3\)
Source: Myschool Past Questions Archive (Record #59003)
Chemistry
WAEC / WASSCE 2020
Stoichiometry, Mole Concept & Volumetric Analysis
The initial volume and pressure of a given mass of gas is V and 3.P. What is its pressure if its volume is increased to 2V at constant temperature?
A
3 P
B
2P
C
\(frac{3}{2}\) P
D
\(frac{2}{3}\) P
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #59006)