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Chemistry
WAEC / WASSCE 2001
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
A gas was evolved when a sample of gastric juice reacted with sodium trioxocarbonate (IV) . The gas evolved was
A
NH3
B
SO2
C
HCI
D
CO2
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Gastric juice is made up of hydrochloric acid, digestive enzymes, and other substances that help absorb nutrients. However, whenever a carbonate(IV) salt reacts with an acid (HCl), CO\(_2\) is evolved.
Source: Myschool Past Questions Archive (Record #36846)
Chemistry
WAEC / WASSCE 2001
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
It can be concluded that gastric juice
A
contains enzymes
B
is acidic
C
is a mixture
D
has pH value of 7
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Gastric juice is made up of hydrochloric acid, digestive enzymes, and other substances that help absorb nutrients. It is highly acidic.
Source: Myschool Past Questions Archive (Record #36847)
Chemistry
WAEC / WASSCE 2001
Periodic Table & Periodicity
Solution
What does ∆H represent in the following equation ? Cl(g) + e- → CI- (g); ∆H = - 363 kJ mol-1
A
lonization energy
B
Electron affinity
C
Dissociation energy
D
Heat of atomization
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Electron affinity is defined as the amount of energy released when an electron is added to a neutral atom to form an anion.
From the reaction, an electron is added to a neutral atom, Cl, and an anion Cl- is formed. Therefore, the correct answer is option B
Source: Myschool Past Questions Archive (Record #36848)
Chemistry
WAEC / WASSCE 2001
Chemical Energetics & Thermochemistry
Solution
Consider the following equation: Ag+ (aq) + CI-(aq) → Ag+CI- (s) ; ∆H = - 65.7 kJmol-1. From the equation, it can be deduced that
A
direct combination is involved and the reaction is endothermic
B
a solid is formed and heat is evolved
C
activation energy is high and a catalyst is required
D
the reaction is endothermic and occurs at high temperature
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
From the chemical equation, the product Ag\(^+\) Cl\(^-\) is solid and for the fact that H is -ve, it is exothermic i.e heat was evolved. Option B is the correct answer.
Source: Myschool Past Questions Archive (Record #36849)
Chemistry
WAEC / WASSCE 2001
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
A reaction is represented by the equation below. A2(g) + B2(g) → 2AB(g); ∆H = +X kJmol-1 Which of the following statements about the system is correct?
A
The reaction goes to completion at equilibrium
B
The forward reaction is exothermic
C
At equilibrium increase in temperature favours the reverse reaction
D
Pressure has no effect on the equilibrium mixture
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The total number of moles of gaseous substances on the LHS = The total number of moles of gaseous product on the RHS.
1 + 1 = 2
2 = 2
Therefore, pressure has no effect on the system in equilibrium.
Source: Myschool Past Questions Archive (Record #36851)
Chemistry
WAEC / WASSCE 2001
Oxidation, Reduction & Redox Reactions
Solution
What is the oxidation number of nitrogen in Al(NO\(_3\))\(_3\)?
A
+ 1
B
+ 3
C
+ 5
D
+ 6
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The oxidation number of Al = +3 , O = - 2, N =? in Al(NO\(_3\) )\(_3\)
Al(NO\(_3\) )\(_3\) = 0
Al + 3N + 3(O3) = 0
+3 + 3N + 3(-2 X 3) = 0
3N = 18 - 3
N = 15/3
N = + 5 - Option C
Source: Myschool Past Questions Archive (Record #36852)
Chemistry
WAEC / WASSCE 2001
Oxidation, Reduction & Redox Reactions
Solution
What is oxidized in the reaction represented by the following equation? 3CU + 8HNO3 → 3Cu(NO3)2 + 2NO + 4H2O
A
Oxygen
B
Hydrogen
C
Nitrogen
D
Copper
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Copper is oxidized because there is an increase of oxidation number from 0 (LHS) to +2 (RHS).
Source: Myschool Past Questions Archive (Record #36853)
Chemistry
WAEC / WASSCE 2001
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
Which of the following substances decomposes when an electric current is passed through it?
A
Glucose solution
B
Zinc rod
C
Hydrochloric acid
D
Tetrachloromethane
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Glucose does not decompose when an electric current passes through it because it is a non-electrolyte and does not conduct electricity. However, hydrochloric acid (HCl) does decompose when an electric current passes through it because it is a strong electrolyte.
Source: Myschool Past Questions Archive (Record #36855)
Chemistry
WAEC / WASSCE 2001
Electrolysis & Electrochemical Cells
Solution
A concentrated solution containing H+, Cu2+,OH- and CI- was electrolyzed using platinum electrodes which of the ions will be discharged at the cathode?
A
H+
B
Cu2+
C
OH-
D
CI-
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
When using a platinum electrode, copper ions (Cu2+) are deposited at the cathode, while hydrogen ions (H+) remain in solution.
Here's what happens during the electrolysis of a copper sulfate solution using a platinum cathode:
Cathode: Copper ions are attracted to the negative cathode and are deposited as a reddish layer of pure copper
Anode: Oxygen gas is liberated
Electrolyte: The blue color of the electrolyte disappears and it becomes dilute sulfuric acid. The less reactive a metal, the more readily its ion is reduced on the electrode surface.
Source: Myschool Past Questions Archive (Record #36856)
Chemistry
WAEC / WASSCE 2001
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Given that the order of reactivity of four metals is P>Q>R>S, which of the following reactions is feasible?
A
S + P+ → P + S +
B
Q + S+ → S + Q+
C
R + P+ → P + R+
D
S + Q+ → Q + S+
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
When a metal gives out an electron,it becomes positively charged. The most reactive metal is P, but from the equations given in the options, P should become P+ once it gives out an electron but no option as such. Then we opt for the next most reactive which is Q. If Q gives out an electron, it becomes Q+ while S is the less reactive. Option B is feasible.
Source: Myschool Past Questions Archive (Record #36859)
Chemistry
WAEC / WASSCE 2001
Electrolysis & Electrochemical Cells
Solution
In the electrolysis of CuSO4(aq) using copper electrodes, the reaction at the anode is
A
discharge of SO4 2-
B
discharge of OH-
C
dissolution of copper electrode
D
evolution of oxygen
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
When copper electrodes are used to electrolyze an aqueous copper sulfate solution, the following happens at the anode:
Copper loses electrons: Copper atoms at the anode lose electrons, forming copper ions that go into the solution.
Anode dissolves: The anode slowly dissolves away as the electrolysis continues.
Copper ions are generated: Copper ions are generated at the anode. In summary, there is dissolution of copper electrode - Option C
Source: Myschool Past Questions Archive (Record #36861)
Chemistry
WAEC / WASSCE 2001
Electrolysis & Electrochemical Cells
Solution
A feasible cell was constructed by joining the two half cells below. Cu\(^{2+}\) (aq) + 2e\(^-\) → Cu(s) E\(^0\) = +0.34 V; Zn\({^2+}\) + 2e\(^-\) → Zn\((_s)\) E\(^0\) = - 0.76V. What is the standard e.m.f. of the cell?
A
- 1.1V
B
- 0.42V
C
+0.42V
D
+1.1V
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
The standard e.m.f. of a cell is calculated by subtracting the standard reduction potential of the anode from the standard reduction potential of the cathode:
E\(^0\)\(_{cell}\) = E\(^0\)\(_{cathode}\) - E\(^0\)\(_{anode}\)
Since E\(^0\)\(_{Cu^{2+}}\) > E\(^0\)\(_{Zn^{2+}}\), it can be inferred that Copper is reduced at the cathode while Zinc is oxidized at the anode.
E\(^0\)\(_{cell}\) = E\(^0\)\(_{Cu^{2+}}\) - E\(^0\)\(_{Zn^{2+}}\)
= + 0.34 - (- 0.76)
= + 0.34 + 0.76
= +1.10V
The standard e.m.f. of the cell is +1.10V
Source: Myschool Past Questions Archive (Record #36863)
Chemistry
WAEC / WASSCE 2001
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
Hydrogenation of butene yields
A
butyne
B
butane
C
pentence
D
butanol
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Hydrogenation reaction is the addition reaction of Hydrogen molecule, H2. Adding H2 to an unsturated Hydrocarbon will be possible if and only if the double bond is broken in order for the H2 to get added up. This will increase the number of Hydrogen and product will change from C4H8 to C4H10 which is butane.
Source: Myschool Past Questions Archive (Record #36865)
Chemistry
WAEC / WASSCE 2001
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
Benzene produces more soot than ethene on burning because benzene
A
has a higher molar mass
B
has a higher degree of unsaturation
C
undergoes substitution and addition reactions
D
is a liquid at room temperature
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Benzene has a higher carbon content than other saturated hydrocarbons, like ethene. This invariably means it has a higher molar mass. When benzene burns, it forms elementary carbon, which causes it to burn with a sooty flame. Benzene is a member of the aromatic hydrocarbon family, which are nonpolar molecules that are usually colourless liquids or solids.
Source: Myschool Past Questions Archive (Record #36866)
Chemistry
WAEC / WASSCE 2001
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
One of the products of combustion of pentane in excess air is
A
pentanol
B
pentene
C
nitrogen (ll) oxide
D
carbon (IV) oxide
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Combustion of Hydrocarbons will usually yield two products: CO2 and H2O. Pentane is an Hydrocarbon, hence one of it's product on combustion will be Carbon(iv)oxide
Source: Myschool Past Questions Archive (Record #36871)