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Chemistry
WAEC / WASSCE 2019
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
Which of the following compounds is formed by the oxidation of ethanol?
A
C\(_2\)H\(_4\)CO\(_2\)H
B
C\(_2\)H\(_5\)CO\(_2\)H
C
CH\(_3\)OH
D
CH\(_3\)CO\(_2\)H
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
-Potassium dichromate solution is acidified with dilute sulphuric acid to oxidise ethanol into ethanoic acid.
Source: Myschool Past Questions Archive (Record #58161)
Chemistry
WAEC / WASSCE 2019
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
What is the characteristic of the gas liberated when dilute hydrochloric acid is added to Iron(ii)sulphide?
A
turns lime water milky
B
decolorizes bromine water
C
gives a pop sound
D
turns lead(ii)ethanoate paper black
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
- Iron sulfide reacts with hydrochloric acid, releasing hydrogen sulfide: FeS + 2HCl → FeCl\(_2\) + H\(_2\)S.
- Hydrogen sulfide reacts with lead acetate to form lead sulfide and thus produces a coloration on the paper which will vary from yellow to black, depending upon the amount of hydrogen sulfide present.
Source: Myschool Past Questions Archive (Record #58162)
Chemistry
WAEC / WASSCE 2019
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
An organic compound contains 72% carbon, 12% hydrogen and 16% oxygen by mass. What is the empirical formula of the compound?
[ H = 1.0. C = 12.0, O = 16.0 ]
A
C\(_3\)H\(_8\)O
B
C\(_6\)H\(_{12}\)O
C
C\(_6\)H\(_{12}\)O\(_2\)
D
C\(_{12}\)H\(_{12}\)O\(_{11}\)
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
C = 72 / 12 H = 12 / 1 O = 16 / 16
C = 6 H = 12 O = 1
: EMPIRICAL FORMULA
C\(_6\)H\(_{12}\)O
Source: Myschool Past Questions Archive (Record #58163)
Chemistry
WAEC / WASSCE 2019
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
When excess chlorine is mixed with ethane at room temperature, the product formed is?
A
1,2-dichloroethane
B
1,2-dichloroethene
C
1,1-dichloroethane
D
1,1-dichloroethene
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
- The chemical compound 1,2-dichloroethane, commonly known as ethylene dichloride (EDC), is a chlorinated hydrocarbon
Source: Myschool Past Questions Archive (Record #58165)
Chemistry
WAEC / WASSCE 2019
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
Which of the following reagents could be used to distinguish between propan-1-ol and propan-2-ol ?
A
H+ / K2Cr2O7
B
I\(_2\) / OH\(^-\)
C
CH\(_3\)COOH
D
NaCl
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The reagent I\(_2\) / OH\(^-\) (iodine in alkaline solution) is used for the iodoform test, which identifies compounds containing a methyl ketone group or a methyl hydroxy group (specifically a secondary alcohol with the structure CH\(_3\)CH(OH)R).
Propan-2-ol is a secondary alcohol (CH\(_3\)CH(OH)CH\(_3\)) that possesses the required methyl group adjacent to the hydroxyl-bearing carbon. It reacts with I\(_2\) / OH\(^-\) to produce a characteristic yellow precipitate of iodoform (CHI\(_3\).
Propan-1-ol is a primary alcohol (CH\(_3\)CH\(_2\)CH\(_2\)OH) and does not have this specific structure. Consequently, it gives a negative result (no yellow precipitate)
Source: Myschool Past Questions Archive (Record #58170)
Chemistry
WAEC / WASSCE 2019
Reaction Rates & Chemical Equilibrium
If a catalyst is added to a system, the temperature and the pressure remain constant, there would be no effect on the?
A
activation energy of the reaction
B
rate of the reaction
C
rate of the reverse reaction
D
heat of reaction
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 #58171)
Chemistry
WAEC / WASSCE 2019
Oxidation, Reduction & Redox Reactions
Solution
consider the following reaction equation: 2NH\(_3 \) .+ 3Cl\(_2\) → N2 + 6HCl.
NH\(_3\) is acting as?
A
a reducing agent
B
a dehydrating agent
C
a drying agent
D
an oxidizing agent
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
- As a reducing agent, Ammonia reacts with chlorine to create nitrogen gas and hydrogen chloride vapour in the first step.
Source: Myschool Past Questions Archive (Record #58172)
Chemistry
WAEC / WASSCE 2019
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
The oxidation of chromium in Cr\(_2\)O\(_7\)\(^{2-}\) ?
A
+4
B
+5
C
+6
D
+7
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Cr\(_2\)O\(_7\)\(^{2-}\)
Cr\(_2\)O\(_7\) = - 2
Cr\(_2\) + O\(_7\) = - 2
2Cr + 7(-2) = - 2
2Cr - 14 = - 2
2Cr = -2 + 14
2Cr = 12
Cr = \(\frac{12}{2}\)
Cr = + 6
Source: Myschool Past Questions Archive (Record #58174)
Chemistry
WAEC / WASSCE 2019
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
The process by which alkanoic acid reacts reversibly with alkanols is known as?
A
saponification
B
esterification
C
carboxylation
D
halogenation
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 #58176)
Chemistry
WAEC / WASSCE 2019
Reaction Rates & Chemical Equilibrium
Solution
consider the reaction represented by the following equation: 2SO\(_2\) + O\(_2\) ⇌ 2SO\(_3\)
A decrease in the pressure of the reaction would
A
decrease in the concentration of SO\(_2\)
B
have no effect on the reaction
C
shift the equilibrium position to the left
D
shift the equilibrium position to the right
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
decrease in pressure favors the side with higher volume thus the equilibrium position will shift to the left
Source: Myschool Past Questions Archive (Record #58181)
Chemistry
WAEC / WASSCE 2019
Kinetic Theory of Matter & Gas Laws
Solution
In a mixture of gases which do not react chemically together, the pressure of the individual gas is?
A
atmospheric pressure
B
vapor pressure
C
total pressure
D
partial pressure
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The pressure exerted by an individual gas in a mixture is known as its partial pressure
Source: Myschool Past Questions Archive (Record #58186)
Chemistry
WAEC / WASSCE 2019
Air & Environmental Chemistry
Solution
Biotechnology is applied in the?
A
treatment of sewage
B
treatment of water
C
purification of chemicals
D
purification of metals
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
There are several wastewater treatment methods based on biotechnology that are used worldwide. It includes Activated Sludge, Oxidation Ponds, Tricking Filters, Bio-filters and Anaerobic treatment. All the methods are part of the biological wastewater treatment and use microbes to treat organic waste in sewage.
Source: Myschool Past Questions Archive (Record #58190)
Chemistry
WAEC / WASSCE 2019
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
which of the following organic compounds has the lowest boiling point?
A
C\(_6\)H\(_14\)
B
C\(_5\)H\(_12\)
C
C\(_4\)H\(_10\)
D
( CH\(_3\) )\(_3\)
medium Difficulty
Verified Correct Answer: Option D
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.
- However; branched alkanes normally exhibit lower boiling points than unbranched alkanes of the same carbon content. This occurs because of the greater van der Waals forces that exist between molecules of the unbranched alkanes
Source: Myschool Past Questions Archive (Record #58427)
Chemistry
WAEC / WASSCE 2019
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
Consider the following reaction represented by the following equation:
C\(_2\)H\(_2\) \(^{H_2}_{→}\) X \(^{H_2}_{→}\) Y. X and Y respectively are?
A
ethane and ethene
B
ethene and ethane
C
ethyne and ethene
D
ethane and ethyne
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The reaction between ethyne (C₂H₂) and hydrogen (H₂) is a hydrogenation reaction, specifically an addition reaction where hydrogen atoms add across the triple bond of ethyne, breaking the triple bond to form a C=C first, i.e ethene. Then on further reaction, the C=C reacts with H\(_2\), breaking the C=C to form a C-C bond. i.e ethane (C₂H₆).
C\(_2\)H\(_2\) \(^{H_2}_{→}\) X \(^{H_2}_{→}\) Y.
C\(_2\)H\(_2\) \(^{H_2}_{→}\) C\(_2\)H\(_4\) \(^{H_2}_{→}\) C\(_2\)H\(_6\)
Source: Myschool Past Questions Archive (Record #58435)
Chemistry
WAEC / WASSCE 2019
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which of the following substances can be classified as heavy chemicals?
A
CaOCl\(_2\)
B
H\(_2\)SO\(_4\)
C
AgNO\(_3\)
D
CaO
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
- heavy chemicals are produced and handled in large lots and are often in a crude state.
- Some examples of bulk chemicals are ammonia, sulfuric acid, and sodium hydroxide
- Fine chemicals are single, pure and complex chemicals that are only produced in small amounts
Source: Myschool Past Questions Archive (Record #58441)