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Chemistry
UTME / JAMB 2007
Metals, Transition Elements & Extraction
Solution
The reddish-brown rust on iron roofing sheets consists of
A
Fe3+(H2O)6
B
FeO.H2O
C
Fe2O3.3H2O
D
Fe3O4.2H2O
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
The chemical formula for rust is Fe\(_2\)O\(_3\).xH\(_2\)O, which represents hydrated iron(III) oxide, where "x" indicates the variable amount of water molecules associated with the iron oxide.
Source: Myschool Past Questions Archive (Record #3755)
Chemistry
UTME / JAMB 2007
Chemical Energetics & Thermochemistry
Solution
Na\(_2\)S\(_2\)O\(_3\)(aq) + 2HCl(aq) → 2NaCl(aq) + H\(_2\)O(l)
Which of the following would introduce the greatest increase in the rate of the chemical reaction above?
A
An increase in temperature and decrease in the concentration of the reactant
B
A decrease in the volume and increase in the pressure of the reactant
C
A decrease in the temperature and an incease in the concentration of the reactant
D
An increase in temperature and an increase in the concentration of the reactant
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Generally speaking, all neutralization reactions are considered exothermic, meaning they release heat during the reaction; this is because the formation of water molecules from the hydrogen ions of an acid and hydroxide ions of a base is a highly stable bond formation, releasing energy in the process.
In every exothermic reaction, a decrease in temperature will favour the forward reaction,likewise increasing the concentration of the reactant. Option C
Source: Myschool Past Questions Archive (Record #3768)
Chemistry
UTME / JAMB 2007
Organic Chemistry II: Functional Groups, Polymers & Biomolecules
Solution
The tincture of iodine means iodine dissolved in
A
ethanol and water
B
bromine chloride
C
chlorine water
D
water
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Tincture of iodine is iodine dissolved in ethanol and water. It's also known as iodine tincture or weak iodine solution. Tincture of iodine is a topical antiseptic solution that contains iodine, alcohol, and water. It's used to treat wounds, prevent infections, and disinfect surfaces.
Source: Myschool Past Questions Archive (Record #3770)
Chemistry
UTME / JAMB 2007
Reaction Rates & Chemical Equilibrium
Solution
Cu\(^{2+}\)(aq) + 4NH\(_3\)(g) ↔ [Cu(NH\(_3\))\(_4\)]\(^{2+}\)(aq)
In the reaction above, what is the effect of precipitating Cu\(^{2+}\)(aq) as CuS(s)?
A
NH3(g) concentration will decrease
B
more NH3(g)
C
The equilibrium will shift to the right
D
There will be no effect
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The precipitation of Cu\(^{2+}\) as CuS decreases the concentration of Cu\(^{2+}\) in the solution. According to Le Chatelier's principle, the equilibrium will shift to the left to counteract this decrease.
Precipitating Cu\(^{2+}\) as CuS shifts the equilibrium to the left, decreasing the concentration of [Cu(NH\(_3\))\(_4\)]\(^{2+}\). Hence more of the reactant will be formed.i.e NH\(_3\)
Source: Myschool Past Questions Archive (Record #3772)
Chemistry
UTME / JAMB 2007
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Copper and silver metals are commonly used as coin because they are
A
easily reduced
B
not easily reduced
C
easily oxidized
D
not easily oxidized
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Copper and Silver metals are commonly used as coins because they are not easily oxidized. They are resistant to oxidation, meaning they don't easily react with oxygen in the air to form oxides. This property helps preserve the coin's appearance and structure over time.
Source: Myschool Past Questions Archive (Record #3774)
Chemistry
UTME / JAMB 2007
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which of the following sets of metals dissolves in dilute HCl?
A
Fe, Sn and Cu
B
Mg, Fe and Cu
C
Mg, Sn and Fe
D
Cu, Mg and Sn
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Mg, Sn and Fe all dissolve in dilute HCl because they are more reactive and have a greater tendency to lose electrons to form ions. In contrast, Cu does not readily dissolve in dilute HCl.
Source: Myschool Past Questions Archive (Record #3784)
Chemistry
UTME / JAMB 2007
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
If chlorine is bubbled into water and the resulting yellowish-green solution is exposed to bright sunlight for a while, the solution will decompose giving out
A
oxygen and leaving behind aqueous hydrochloric acid
B
chlorine and oxygen
C
oxygen, hydrogen and chlorine
D
oxygen, thereby producing hypochlorous acid
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
When chlorine reacts with water in the presence of sunlight, it produces oxygen gas and hydrochloric acid as the primary products; essentially, the sunlight breaks down the chlorine in water, liberating oxygen gas.
2Cl\(_2\) + 2H\(_2\)O → 4HCl + O\(_2\)
Source: Myschool Past Questions Archive (Record #3791)
Chemistry
UTME / JAMB 2007
Chemical Energetics & Thermochemistry
Solution
H\(_3\)PO\(_4\)(aq) + H\(_2\)O(l) ↔ H\(_2\)PO\(^{4-}\)(aq) + H\(_3\)O\(^+\)(aq) \DeltaH = -13kJ at 298K
In the reaction above, an increase in temperature would
A
slow down the reverse reaction
B
have no effect on the reaction
C
favour the reverse reaction
D
favour the forward reaction
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
In an exothermic reaction, an increase in temperature will favour the reactants (shift the reaction towards the left), meaning the reaction will produce less product as heat is considered a product in an exothermic reaction; according to Le Chatelier's principle, the system will try to counteract the added heat by favouring the reactant side. Thus, the reverse reaction will be favoured.
Source: Myschool Past Questions Archive (Record #3796)
Chemistry
UTME / JAMB 2007
Oxidation, Reduction & Redox Reactions
Solution
The reaction that takes place in Daniell's cell is
A
direct combination
B
redox
C
double decomposition
D
neutralization
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
A Daniell cell undergoes a redox reaction where zinc is oxidized at the anode, releasing electrons that travel through a circuit to the cathode where copper ions are reduced to solid copper, generating an electric current.
Oxidation half-reaction: Zinc metal (Zn) is oxidized to zinc ions (Zn\(^{2+}\)) at the anode, releasing electrons. Zn(s) → Zn\(^{2+}\) + 2e\(^-\)
Reduction half-reaction: Copper ions Cu\(^{2+}\) are reduced to solid copper metal (Cu) at the cathode, accepting electrons. Cu\(^{2+}\) + 2e\(^-\) → Cu
Overall reaction: Zn (s) + Cu\(^{2+}\) (aq) → Zn\(^{2+}\) (aq) + Cu (s).
Source: Myschool Past Questions Archive (Record #3797)
Chemistry
UTME / JAMB 2007
Electrolysis & Electrochemical Cells
What happens when zinc rod is immersed in copper (II) tetraoxosulphate (VI) solution?
A
The blue colour of the solution disappears
B
Electrons flow from copper to zinc
C
The zinc rod remain undissolved
D
The copper generate more copper ions
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 #3805)
Chemistry
UTME / JAMB 2007
Chemical Energetics & Thermochemistry
C\(_2\)H\(_4\)(g) + H\(_2\)(g) → C\(_2\)H\(_6\)(g) \DeltaH = -137kJ mol-1
The reaction represented above is
A
exothermic
B
spontaneous
C
endothermic
D
in equilibrium
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 #3808)
Chemistry
UTME / JAMB 2007
Electrolysis & Electrochemical Cells
How long would it take to deposit 0.08g of copper from CuCl\(_2\) solution by passing a current of 0.5A?
[Cu = 64, 1F = 96500 C mol-1]
A
6 mins
B
8 mins
C
24 mins
D
48 mins
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 #3813)
Chemistry
UTME / JAMB 2007
Metals, Transition Elements & Extraction
Solution
Tartaric acid is used industrially to
A
make baking powder
B
make fruit juices
C
remove rust
D
dry substance
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Tartaric acid is used industrially as an acidulant in food products like carbonated drinks, jellies, and baking powder, as well as in metal cleaning and polishing processes due to its chelating properties; it also finds applications in textile processing and certain photographic development procedures.
The major industrial use of tartaric acid is as an acidulant in the food and beverage industry, primarily used to add a tart flavour to products like carbonated drinks, fruit jellies, candies, and wine, often in combination with other acids to achieve the desired taste profile; it is also used as a leavening agent in baking due to its reaction with baking soda when heated.
Source: Myschool Past Questions Archive (Record #3818)
Chemistry
UTME / JAMB 2007
Chemical Energetics & Thermochemistry
Dissolving some pellets of NaOH in water would result in
A
a decrease in the free energy of the solution
B
a decrease in the entropy of the solution
C
a lowering of the temperature of te solution
D
an increase in the entropy of the solution
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 #3822)
Chemistry
UTME / JAMB 2007
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Calculate the number of moles of HCl present in 20cm3 of a 0.75M solution of the acid
A
0.015 mole
B
0.038 mole
C
3.800 moles
D
1.500 moles
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Number of moles = (conc. in mol/dm3*volume in cm3)/1000
(0.75 * 20)/100 = 0.015 mole
Source: Myschool Past Questions Archive (Record #3826)