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Chemistry
WAEC / WASSCE 2022
Atomic Structure and Periodic Table
Solution
Ionization energy increases across the period in the periodic table because
A
atomic number increases
B
effective nuclear charge increases
C
mass number decreases
D
screening effect decreases
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
As the nuclear charge increases, its attraction for the outermost electron increases and so more energy is required to remove the outermost electron. Hence, the ionization energy increases.
Source: Myschool Past Questions Archive (Record #65877)
Chemistry
WAEC / WASSCE 2022
Atomic Structure and Periodic Table
Solution
Which of the following properties indicate that an element is a metal. It
I. reacts with oxygen to form an acidic oxide
II. forms ionic chlorides
III. has variable oxidation states
IV. displaces hydrogen from dilute HCl
A
I and III only
B
I and II only
C
II and IV only
D
I, II, III and IV
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
- Ionization behaviour; The atoms of non-metals usually have four to seven valence electrons. They have a great tendency to ionize by accepting electrons to form negative ions.
- Reaction with acids; A metal which is more electro positive than hydrogen readily displaces the hydrogen ion, H+, from an acid.
Source: Myschool Past Questions Archive (Record #65878)
Chemistry
WAEC / WASSCE 2022
Atomic Structure and Periodic Table
Solution
The electron configuration of carbon atom in its excited state is
A
1s\(^{2}\)2s\(^{2}\)2px\(^{2}\)2py\(^{0}\)
B
1s\(^{2}\)2s\(^{2}\)2px\(^{1}\)2py\(^{1}\)
C
1s\(^{2}\)2s\(^{1}\)2px\(^{1}\)2py\(^{1}\)2pz\(^{1}\)
D
1s\(^{1}\)2s\(^{2}\)2px\(^{1}\)2py\(^{1}\)
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
- So any electron configuration in which the last electron (again, the valence electron) is in a higher energy orbital, this element is said to be in an excited state.
- When a carbon atom becomes excited by absorbing energy, one of its 2s electrons is promoted into the 2p sublevel.
Source: Myschool Past Questions Archive (Record #65879)
Chemistry
WAEC / WASSCE 2022
Acids, Bases, and Salts
Solution
An oxide has the following properties. It
I. is a white powder
II. reacts with HCI.
III. reacts with NaOH
IV. is insoluble in water
The oxide is
A
alkaline
B
amphoteric
C
acidic
D
neutral
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
An amphoteric oxide is an oxide that can act as either an acid or base in a reaction to produce a salt and water.
Source: Myschool Past Questions Archive (Record #65880)
Chemistry
WAEC / WASSCE 2022
Atomic Structure and Periodic Table
Solution
Which of the following statements about atoms of a metal is correct? They
A
readily accept electrons
B
are soft
C
are held together by covalent bond
D
are held together by a sea of electron cloud
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Metals are effectively lots of positively charged ions with a cloud/sea of delocalised electrons. This means the electrons are free to move throughout the metal, and is also why metals can conduct electricity as the electrons can move. The more delocalised electrons a metal has, the stronger it will be held together.
Source: Myschool Past Questions Archive (Record #65881)
Chemistry
WAEC / WASSCE 2022
Atomic Structure and Periodic Table
Solution
The atom with the electron configuration
1s\(^{2}\)2s\(^{2}\)2p63s\(^{2}\)3p\(^{6}\)3d\(^{10}\)4s\(^{2}\)4p\(^{4}\) is in
A
period 4, p- block
B
period 3, p- block
C
period 4, d- block
D
period 3, d- block
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Selenium is a chemical element with the symbol Se and atomic number 34. It is a non-metal
Source: Myschool Past Questions Archive (Record #65882)
Chemistry
WAEC / WASSCE 2022
Atomic Structure and Periodic Table
Solution
Electropositivity of elements across the periodic table normally
A
remains constant down the group
B
increases across the period
C
decreases across the period
D
decreases down the group
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Electropositivity is known to increase down groups and decrease across periods in the modern periodic table (i.e., electropositivity decreases from left to right and it increases from up to down).
Source: Myschool Past Questions Archive (Record #65883)
Chemistry
WAEC / WASSCE 2022
Matter & Separation Techniques
Solution
Consider the following table
Substitute
Meltig point / ºC
Boiling point / ºC
P
- 78
-25
Q
- 8
40
R
- 6
150
S
44
280
Which of the substances is a liquid at room temperature and rapidly evaporates on exposure to air?
A
P
B
Q
C
R
D
S
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Q has slightly lower boiling point which when expose to air may evaporate rapidly.
Source: Myschool Past Questions Archive (Record #65884)
Chemistry
WAEC / WASSCE 2022
Acids, Bases, and Salts
Solution
Which of the following oxides is amphoteric?
A
Carbon(II) oxide
B
Nitrogen(IV) oxide
C
Lead(II) oxide
D
Calcium oxide
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Aluminium oxide is an amphoteric oxide. With sodium hydroxide solution, it produces water and sodium aluminate (NaAlO2). The other common examples of amphoteric oxides include SnO, ZnO, and PbO. Al2O3 is an amphoteric oxide.
Source: Myschool Past Questions Archive (Record #65885)
Chemistry
WAEC / WASSCE 2022
Matter & Separation Techniques
Solution
Which of the following processes occur during fractional distillation of petroleum?
A
Condensation and diffusion
B
Diffusion and evaporation
C
Diffusion and sublimation
D
Evaporation and condensation
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Fractional distillation is a series of processes of evaporation and condensation at a number of points in a vertical column.
Source: Myschool Past Questions Archive (Record #65886)
Chemistry
WAEC / WASSCE 2022
Stoichiometry & Mole Concept
Solution
If the molar mass of X(HCO3)\(_{2}\) is 162 g mol\(^{-1}\), determine the relative atomic mass of X.
[H = 1.0, C = 12.0, 0 = 16.0]
A
40
B
48
C
61
D
101
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Molar mass of X(HCO3)2 = X+(1+12+(16*3))2=162
=X + (13+48)2=162
X + 122=162
X=162-122
X=40
Source: Myschool Past Questions Archive (Record #65887)
Chemistry
WAEC / WASSCE 2022
Matter & Separation Techniques
Solution
Charcoal is used in the decolourization of sugar because of its
A
absorption property.
B
amorphous property.
C
oxidizing property.
D
adsorption property.
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Wood charcoal is used to decolourise sugar because it has a highly porous structure, providing a large surface area for adsorption. Therefore, it adsorbs coloured material from sugar.
Source: Myschool Past Questions Archive (Record #65888)
Chemistry
WAEC / WASSCE 2022
Matter & Separation Techniques
Solution
The first definition of an element was made by
A
J. Dalton.
B
A. Lavoisier.
C
R. Boyle.
D
J. J. Thompson.
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The word element was first given by Rebert Boyle. It is defined as the simplest chemical substance that cannot be broken down during a chemical reaction
Source: Myschool Past Questions Archive (Record #65889)
Chemistry
WAEC / WASSCE 2022
Stoichiometry & Mole Concept
Solution
Which of the following scientists formulated the law of conservation of mass?
A
A. Lavoisier
B
J. Dalton
C
R. Boyle
D
J. Proust
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Law of conservation of mass was given by Antoine Lavoisier in 1744. According to this law, "Matter can neither be created nor destroyed in a chemical reaction".
Source: Myschool Past Questions Archive (Record #65890)
Chemistry
WAEC / WASSCE 2022
Stoichiometry & Mole Concept
Diagram
Solution
Which of the following sketches is a graphical representation of Boyle's law?
Attached Figure / Diagram
A
A
B
B
C
C
D
D
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Boyles law states that the volume of a given mass of gas is inversely proportional to pressure at constant temperature.
Source: Myschool Past Questions Archive (Record #65891)