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Chemistry
WAEC / WASSCE 2021
Acids, Bases, pH & Salts
Which of the graphs illustrates the variation of the pH of a given volume of strong acid solution (y-axis) with the volume of strong base titrated against its (x-axis)?
A
I
B
II
C
III
D
IV
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 #61894)
Chemistry
WAEC / WASSCE 2021
Chemical Energetics & Thermochemistry
Which of the graphs illustrates the variation of the solubility of a salt in water (y-axis), with an increase in temperature (x-axis) if the dissolution process is exothermic?
A
I
B
II
C
III
D
IV
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #61897)
Chemistry
WAEC / WASSCE 2021
Organic Chemistry I: Hydrocarbons & Crude Oil
The formation of ethene from dehydration of ethanol can be described as-------
A
an addition reaction
B
an elimination reaction
C
an oxidation reaction
D
a substitution reaction
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 #61898)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following gasses is highly soluble in water at room temperature
A
ammonia
B
carbon (IV) oxide
C
chlorine
D
nitrogen
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 #61966)
Chemistry
WAEC / WASSCE 2021
Particulate Nature of Matter, Laws & Formulae
A molecular of phosphorus is
A
diatomic
B
triatomic
C
tetraatomic
D
monoatomic
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 #61967)
Chemistry
WAEC / WASSCE 2021
Acids, Bases, pH & Salts
The most common method of preparing insoluble salts is by
A
filtration
B
decomposition
C
neutralization
D
double decomposition
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #61968)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
What number of moles of oxygen would exert a pressure of 10 atm at 320 K in an 8.2 dm\(^{2}\) cylinder?
[R = 0.082 atm dm\(^{3}\) mol\(^{-1}\) K\(^{-1}\)]
A
0.32
B
1.56
C
3.13
D
31.25
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 #61973)
Chemistry
WAEC / WASSCE 2021
Metals, Transition Elements & Extraction
Solution
What would be observed when aqueous ammonia is added in drops and then in excess to a solution of copper(II) ions?
A
blue precipitate is formed which is soluble in excess ammonia
B
brick red precipitate is produced which is insoluble in excess ammonia
C
white precipitate is formed which is excess in ammonia
D
green precipitate is formed which is insoluble in excess ammonia
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
When a few drops of ammonia solution is added to copper(II) ions, a blue precipitate of copper(II) hydroxide is formed.
CuSO₄(aq) + 2NH₃(aq) + 2H₂O(ℓ) ⇌ Cu(OH)₂(s) + (NH₄)₂SO₄(aq)
However, when ammonia solution is added in excess, the blue precipitate re-dissolves to form a deep blue solution of tetraamine copper(II) hydroxide.
Cu(OH)₂(s) + 4NH₃(aq) → [Cu(NH₃)₄](OH)₂(aq). Therefore, the correct answer is option A.
Source: Myschool Past Questions Archive (Record #61982)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
When CuSO\(_{4(aq)}\) is added to Pb(N\(O_3\))\(_{2(aq)}\)--------
A
there would be no visible change
B
a blue precipitate would be formed
C
the resulting solution would become colourless
D
a white precipitate would be formed
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #61985)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
The 25^\circC evaporation of a 100 cm\(^{3}\) solution of \(K_2\)C\(O_3\) to dryness gave 14g of the salt. What is the solubility of \(K_2\)C\(O_3\) at 25^\circC? [\(K_2\)C\(O_3\) = 138]
A
0.01 mol dm\(^{-3}\)
B
0.101 mol dm\(^{-3}\)
C
1.01 mol dm \(^{-3}\)
D
10.0 mol dm\(^{-3}\)
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
solubility( in mol/dm^3) = \(\frac{ mass of salt}{ Molar Mass of salt} = \frac{ 1000cm^3}{ volume of solution in cm^3}\)
\(\frac{14}{138 } = \frac{ 1000cm^3}{ 100}\)
\(\frac{14000}{13800} = 1.01 mol/dm^3\)
Source: Myschool Past Questions Archive (Record #62093)
Chemistry
WAEC / WASSCE 2021
Acids, Bases, pH & Salts
Solution
Student X titrated 25 cm\(^{3}\) of N\(a_2\)CO\(^{3}\) with 0.1 mol dm\(^{-3}\) HCI, using methyl orange as indicator. Student Y carried out the same exercise but used phenolphthalein as an indicator. Which of the following statements about the titration is true?
A
hydrogen chloride gas was released in the reactions in both titrations
B
the titer values obtained from the titration are equal
C
the titer value obtained by X is twice that of Y
D
the titer value obtained by Y is twice that of X
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The titration of sodium carbonate (Na\(_2\)CO\(_3\)) with hydrochloric acid (HCl) occurs in two distinct stages due to the dibasic nature of the carbonate ion.
Because Student X (using methyl orange) titrates through both stages and Student Y (using phenolphthalein) titrates through only the first stage, Student X requires twice the volume of acid to reach the endpoint compared to Student Y.
Source: Myschool Past Questions Archive (Record #62095)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
What is the concentration of a solution which contains 0.28g of potassium hydroxide in 100 cm\(^{3}\) of solution [KOH = 56]
A
0.01 mol dm\(^{-3}\)
B
0.05 mol dm\(^{-3}\)
C
0.10 mol dm\(^{-3}\)
D
0.50 mol dm\(^{-3}\)
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 #62096)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
What is the empirical formula of a hydrocarbon containing 0.160 moles of carbon and 0.640 moles of hydrogen
A
C\(H_2\)
B
C\(H_3\)
C
C\(H_4\)
D
\(C_2\)\(H_4\)
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 #62097)
Chemistry
WAEC / WASSCE 2021
Periodic Table & Periodicity
Which of the following species has the largest ionic radius
A
S\(^{2-}\)
B
K\(^{+}\)
C
CI\(^{-}\)
D
Ca\(^{2+}\)
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 #62098)
Chemistry
WAEC / WASSCE 2021
Stoichiometry, Mole Concept & Volumetric Analysis
Diagram
Solution
Consider the structure above
How many carbon atoms does the parent chain contain?
Attached Figure / Diagram
A
5
B
4
C
3
D
2
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Going by the longest continuous carbon chain, the parent chain contains 4 carbon atoms (2- methyl butanoic acid)
Source: Myschool Past Questions Archive (Record #61990)