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Chemistry
WAEC / WASSCE 2017
Atomic Structure, Orbitals & Nuclear Chemistry
Solution
The reason for the decrease in the atomic size of elements across a period is that
A
nuclear charge increases while the outermost electrons are drawn closer to the nucleus
B
nuclear charge decreases while the outermost electrons are drawn closer to the nucleus
C
valence electrons increase across the period while the valence shell remains constant
D
nuclear charge decreases while the distance of the valence shell from the nucleus is increasing
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
This is caused by the increase in the number of protons and electrons across a period.
Source: Myschool Past Questions Archive (Record #49209)
Chemistry
WAEC / WASSCE 2017
Oxidation, Reduction & Redox Reactions
Solution
The oxidation number of nitrogen in \(Pb(NO_{3})_{2}\) is
A
+2
B
+3
C
+4
D
+5
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
\(Pb(NO_{3})_{2}\) = \(+2 +2N + (-2\times 6) = 0\)
= \(2N = 10\)
⇒ \(N = +5\)
Source: Myschool Past Questions Archive (Record #49213)
Chemistry
WAEC / WASSCE 2017
Periodic Table & Periodicity
Solution
Which of the following arrangements indicates the correct decreasing order of ionization energy of period 3 elements?
A
Na, Al, P, Cl
B
Cl, P, Al, Na
C
Na, P, Cl, Al
D
Al, Na, P, Cl
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
As you move across a period, first ionization energy increases.
Source: Myschool Past Questions Archive (Record #49216)
Chemistry
WAEC / WASSCE 2017
Chemical Bonding & Intermolecular Forces
Solution
Which of the following metals has the strongest metallic bond?
A
\(_{13}Al\)
B
\(_{19}K\)
C
\(_{12}Mg\)
D
\(_{11}Na\)
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Aluminium has the highest magnitude of charge of +3, hence it will form a stronger metallic bond.
Source: Myschool Past Questions Archive (Record #49219)
Chemistry
WAEC / WASSCE 2017
Chemical Bonding & Intermolecular Forces
Which of the following substances does not have van der Waals' forces?
A
Copper
B
Graphite
C
Neon
D
Iodine crystals
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option A.
Source: Myschool Past Questions Archive (Record #49231)
Chemistry
WAEC / WASSCE 2017
Oxidation, Reduction & Redox Reactions
Solution
The oxidation number of X in \(XO_{4}^{3-}\) is
A
+1
B
+3
C
+4
D
+5
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
\(XO_{4}^{3+}\) = \(X + (-2\times 4) = -3\)
\(X = -3+8 = +5\)
Source: Myschool Past Questions Archive (Record #49234)
Chemistry
WAEC / WASSCE 2017
Periodic Table & Periodicity
Solution
The ionization energy is affected by the following factors except
A
distance of the outermost electron(s) from the nucleus
B
size of the positive nuclear charge
C
ability to attract shared electron(s)
D
screening effect of the inner electron(s)
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
These 3 factors affect the ionization energy:
Size of the positive nuclear charge
Size of atom (distance of outermost electron from the nucleus)
Screening effect of inner shell electrons
Source: Myschool Past Questions Archive (Record #49238)
Chemistry
WAEC / WASSCE 2017
Chemical Bonding & Intermolecular Forces
Solution
Which of the following statements is correct?
A
Covalent compounds would readily ionize in solution
B
Covalent compounds consist of ions
C
Hydrogen bond is formed between a metal and a non-metal
D
Ionic compounds in solution would conduct electricity
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
One of the common features of materials with ionic bonds is that they conduct electricity when dissolved in water.
Source: Myschool Past Questions Archive (Record #49243)
Chemistry
WAEC / WASSCE 2017
Chemical Bonding & Intermolecular Forces
The bond angle in tetrahedral molecules such as tetrachloromethane is
A
180.0°
B
109.5°
C
105.5°
D
90.0°
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 #49247)
Chemistry
WAEC / WASSCE 2017
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
The properties of a good primary standard include the following except
A
high molecular mass
B
low molecular mass
C
high degree of purity
D
readily available
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Characters of a good primary standard include: high purity, low reactivity with the air or surrounding environment, low hygroscopicity, large molar mass, a predictable reactivity and readily available.
Source: Myschool Past Questions Archive (Record #49251)
Chemistry
WAEC / WASSCE 2017
Non-Metals & Their Compounds
Solution
The use of diamond in abrasives is due to its
A
high melting point
B
hardness
C
octahedral shape
D
durability
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Diamonds are very hard, they are often used as an abrasive.
Source: Myschool Past Questions Archive (Record #49254)
Chemistry
WAEC / WASSCE 2017
Chemical Energetics & Thermochemistry
Solution
Which of the following statements about endothermic reaction is correct?
A
Activation energy is high
B
A catalyst is required
C
It occurs reversibly
D
Heat energy is absorbed
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Endothermic reactions are those reactions which absorb energy from the surroundings and result in a net decrease in temperature.
Source: Myschool Past Questions Archive (Record #49255)
Chemistry
WAEC / WASSCE 2017
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
A 0.1\(moldm^{-3}\) solution of sodium hydroxide was diluted with distilled water to 0.001\(moldm^{-3}\). What is the dilution factor?
A
1000.00
B
100.00
C
10.00
D
0.01
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The formula to calculate the dilution factor when using concentrations is DF = \(\frac{C_1}{C_2}\), where C\(_1\) is the initial concentration of the stock solution and C\(_2\) is the final concentration of the diluted solution.
Dilution factor= \(\frac{0.1}{0.001}\) = 100
Source: Myschool Past Questions Archive (Record #49260)
Chemistry
WAEC / WASSCE 2017
Non-Metals & Their Compounds
Solution
Graphite and Diamond are similar in that they
A
have octahedral shape
B
have same density
C
form carbon(IV) oxide on combustion
D
conduct electricity
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
A diamond is pure carbon. Graphite is pure carbon. Both will burn to form carbon dioxide.
Source: Myschool Past Questions Archive (Record #49267)
Chemistry
WAEC / WASSCE 2017
Water, Solutions & Solubility
Solution
In a saturated solution at a given temperature, the undissolved solutes are in equilibrium with
A
the solvent
B
dissolved solute particles
C
the saturated solution
D
insoluble solute particles
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
In a saturated solution dissolved solute and undissolved solute are in equilibrium with each other. Is different from A saturated solution is said to be in equilibrium with undissolved solute when the rate of dissolution of the solute equals the rate of crystallization. This means that the amount of solute being dissolved is the same as the amount of solute coming out of solution, resulting in no net change in the concentration of the solution.
Source: Myschool Past Questions Archive (Record #49271)