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Chemistry
UTME / JAMB 1990
Oxidation, Reduction & Redox Reactions
Solution
Cr\(_2\)O\(_7\)\(^{2-}\) + 6Fe\(^{2+}\) + 14H\(^+\) → 2Cr\(^{3+}\) +6Fe\(^{3+}\) + 7H\(_2\)O. In the above , the oxidation number of chromium changed from?
A
+7 to +3
B
+6 to +3
C
+5 to +3
D
-2 to +3
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The oxidation number of Cr in Cr\(_2\)O\(_7\)\(^{2-}\) is
Cr\(_2\)O\(_7\) = - 2
2Cr + ( - 2) x 7 = - 2
2Cr - 14 = - 2
2Cr = - 2 + 14
2Cr = 12
\(\frac{2Cr}{2}\) = \(\frac{12}{2}\)
Cr = + 6
On the RHS, the oxidation number of Cr is +3.
Thus, the oxidation number changed from +6 to +3 - option B.
Source: Myschool Past Questions Archive (Record #12856)
Chemistry
UTME / JAMB 1990
Oxidation, Reduction & Redox Reactions
In the reaction 1O-3 + 5l- + 6H+ → 312 + 3H2O, the oxidizing agent is?
A
H+
B
l-
C
1O-
D
l2
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 #12858)
Chemistry
UTME / JAMB 1990
Chemical Energetics & Thermochemistry
Solution
Fe\(_2\)O\(_{3(s)}\) + 2Al\(_{(s)}\) → Al\(_2\)O\(_3\) + 2Fe\(_{(s)}\). If the heats of formation of Al\(_2\)O\(_3\) and Fe\(_2\)O\(_3\) are - 1670 kJmol\(^{-1}\) and - 822 kJmol\(^{-1}\) respectively, the enthalpy change in kJ for the reaction is ?
A
+2492
B
+848
C
-848
D
-2492
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Heat of formation = Heat of products - Heat of reactants
= - 1670 - (- 822)
= - 1670 + 822
= - 848 kJ
Source: Myschool Past Questions Archive (Record #12860)
Chemistry
UTME / JAMB 1990
Metals, Transition Elements & Extraction
Solution
Iron galvanized with zinc is cathodically protected from corrosion. This is because?
A
zinc has a more positive oxidation potential than iron
B
zinc has less positive oxidation potential than iron
C
bith have the same oxidation potential
D
zinc is harder than iron
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Iron galvanized with zinc is cathodically protected from corrosion because Zinc has a more positive oxidation potential than iron. This means that Zinc will preferentially corrode, acting as a sacrificial anode.
Source: Myschool Past Questions Archive (Record #12861)
Chemistry
UTME / JAMB 1990
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following samples will react fastest with dilute trioxonitrate (V) acid?
A
5 g of lumps of CacO3 at 25°C
B
5 g of powered CacO3 at 25°
C
5 g of lumps of CaCO3 at 50°C
D
5 g of powered CaCO3 AT 50°C
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 #12862)
Chemistry
UTME / JAMB 1990
Chemical Energetics & Thermochemistry
In the reaction:
2Hl(g) ↔ H2(g) + l2(g)' ΔH = 10 kj;
The concentration of iodine in the equilibrium mixture can be increased by?
A
raising the pressure
B
raising the temperature
C
adding a catalyst
D
lowering the pressure
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 #12863)
Chemistry
UTME / JAMB 1990
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following gases can be collected by the upward displacement of air?
A
NO
B
H 2
C
NH3
D
Cl 2
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 #12865)
Chemistry
UTME / JAMB 1990
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
The brown fumes given off when trioxonitrate (V) acid is heated consist of ?
A
NO2 and O2
B
H2O and NO2
C
NO2' O2 and H2O
D
NO, NO2 and H2O
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
decomposition of the acid by heat to produce reddish-brown gas (nitrogen (iv)) which then dissolve in the acid to impart the yellow colour.
Source: Myschool Past Questions Archive (Record #12866)
Chemistry
UTME / JAMB 1990
Acids, Bases, pH & Salts
Which of the following tests will completely identify anyone of surphur (VI) oxide, hydrogen, carbon (IV) oxide and nitrogen (II) oxide?
A
Pass each gas into water and test with blue litmus paper
B
Pass each gas into lime water
C
Expose each gas to atmospheric air
D
Pass each gas to concentrated tetraoxosulphate (IV) acid
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 #12867)
Chemistry
UTME / JAMB 1990
Non-Metals & Their Compounds
In the Haber process for the manufacture of ammonia, the catalyst commonly used is finely divided ?
A
vanadium
B
platinum
C
iron
D
copper
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 #12869)
Chemistry
UTME / JAMB 1990
Acids, Bases, pH & Salts
A metallic oxide which reacts with both HCl and NaOH to give salt and water only can be classified as?
A
an acidic oxide
B
a basic oxide
C
a neutral oxide
D
an amphoteric oxide
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 #12870)
Chemistry
UTME / JAMB 1990
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following metals will liberate hydrogen from steam or dilute acid?
A
Copper
B
Iron
C
Lead
D
Mercury
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 #12871)
Chemistry
UTME / JAMB 1990
Non-Metals & Their Compounds
Coal fire should not be used in poorly ventilated rooms because ?
A
of the accumulation of CO2 which causes dep sleep
B
it is usually too hot
C
of the acumulation of CO which causes suffocation
D
it removes most most of the gases in the rooms
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 #12872)
Chemistry
UTME / JAMB 1990
Metals, Transition Elements & Extraction
Solution
The major component of the slag from the production of iron is?
A
an alloy of calcium and iron
B
coke
C
impure iron
D
calcium trioxosilicate (IV)
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Blast furnace slag is a nonmetallic coproduct produced in the process. It consists primarily of silicates, aluminosilicates, and calcium-alumina-silicates
Source: Myschool Past Questions Archive (Record #12873)
Chemistry
UTME / JAMB 1990
Water, Solutions & Solubility
Solution
Sodium hydroxide should be stored in properly closed containers because it?
A
readily asborbs water vapour to air
B
is easily oxidize by atmospheric oxygen
C
turns golden yellow when exposed to light
D
melts at a low temperature
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
NaOH pellets are deliquescent..so they easily absorb from the atmosphere when exposed
Source: Myschool Past Questions Archive (Record #12874)