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Chemistry
UTME / JAMB 1992
Acids, Bases, pH & Salts
Solution
A sample of orange juice is found to have a pH of 3.80. What is he concentration of the hydroxide ion in the juice?
A
1.6 x 10-4
B
6.3 x 10-11
C
6.3 x 10-4
D
1.6 x 10-11
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
pH + pOH = 14
3.80 + pOH = 14
pOH = 14 - 3.80
pOH = 10.2
Recall that pOH = - log [ OH\(^-\)]
10.2 = - log [ OH\(^-\)]
[ OH\(^-\)] = 10\(^{-10.2}\)
[ OH\(^-\)] = 6.3 x 10\(^{-11}\)
Source: Myschool Past Questions Archive (Record #13157)
Chemistry
UTME / JAMB 1992
Stoichiometry, Mole Concept & Volumetric Analysis
Arrange HCI, CH3COOH, C6H5CH3 in order of increasing conductivity.
A
HCI, CH3COOH, C6H5CH3
B
C6H5CH3, HCI, CH3COOH
C
C6H5CH3, CH3COOH, HCI
D
CH3COOH, C6H5CH3, HCI
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 #13158)
Chemistry
UTME / JAMB 1992
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
How many grams of H2SO4 are necessary for the preparation of 0.175 dm3 of M 6.00 M H2SO4?
(S = 32.06, O = 16.00 H = 1.00)
A
206.0 g
B
103.0 g
C
98.1 g
D
51.5 g
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
1 mole of H2SO4 ≈ 98 gms
0.175 dm3 of 6.0 m H2SO4
1000 cm3 ≈ dm3
(0.175) / (1000) of 6.0 m H2SO4
0.000175 x 6 x 98 ≈ 0.1029 gms
1 dm3 - 1000 cm3
∴ 0.1029 x 1000 = 103 gms
Source: Myschool Past Questions Archive (Record #13198)
Chemistry
UTME / JAMB 1992
Electrolysis & Electrochemical Cells
Copper (II) tetraoxosulphate (VI) solution is electrolyzed using carbon electrodes. Which of the following are produced at the anode and cathode respectively ?
A
Copper and oxygen
B
Oxygen and copper
C
Hydrogen and copper
D
Copper and hydrogen
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 #13199)
Chemistry
UTME / JAMB 1992
Electrolysis & Electrochemical Cells
Solution
Calculate the mass, in kilograms, of magnesium produced by the electrolysis of magnesium (II) chloride in a cell operating for 24 hours at 500 amperes.
A
2.7
B
5.4
C
10.8
D
21.7
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Mg + 2e → 24 gms
2f → 24 gms
2 x 96,500 → 24 gms
Q = (500 x 1440 x 60)
Q = 4320000 C
1 mole of mg = (1) / (2 x 96,500) x (43200000) / (1)
= (24)/(1) = (1036800000) / (193000) = 5372.020725 gms
in leg = (5372.020725) / (1000) = 5.4 leg
Source: Myschool Past Questions Archive (Record #13201)
Chemistry
UTME / JAMB 1992
Oxidation, Reduction & Redox Reactions
S2O2-3 + I2 → S2O62- + 2I-. In reaction above, the oxidizing agent is?
A
S2O32-
B
I2
C
S4O62-
D
I-
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 #13205)
Chemistry
UTME / JAMB 1992
Oxidation, Reduction & Redox Reactions
Solution
\(MnO_2 + 2CI^- + 4H^+ → Mn^{2+} + CI_2 + 2H_2O\).
The changes in oxidation numbers when the manganese, chloride, and hydrogen ions react according to the above equation are respectively?
A
2, 2, 4
B
-1, -2, 4
C
-2, 1, 0
D
2, 4, 0
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
\(MnO_2 + 2CI^- + 4H^+ → Mn^{2+} + CI_2 + 2H_2O\). i.e \(Mn^+ O^{2-} + 2Cl^- + 4H^+\) → \(Mn^{2+} + Cl^0_2 + 2H^+ O^{2-}\)
Mn⇒2 - 4 = -2; Cl ⇒ 0 - 1 = -1; H ⇒ 1-1 = 0.
therefore, the change in the oxidation state of Mn, Cl, and H = -2, -1, and 0.
Source: Myschool Past Questions Archive (Record #13206)
Chemistry
UTME / JAMB 1992
Chemical Energetics & Thermochemistry
Solution
In which of the following is the entropy change positive?
A
H2O(I) → H2O(g)
B
Cu2+(aq) + Fe(s) → Fe2+(aq) + Cu(s)
C
N2(g) + 3H2(g) → 2NH3(g)
D
2HCI(g) → H2(g) + CI2(g)
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Entropy is the measure of the degree of disorderliness or randomness in a system. It will, however, decrease from gaseous to liquid and to solid states and vice versa.
This implies for option A, as you move from reactants(liquid H\(_2\)O) to products(gaseous H\(_2\)O), entropy increases because the level of disorderliness increases. (Just liken it to liquid water that needs to be boiled). Hence \DeltaS = + ve.
Source: Myschool Past Questions Archive (Record #13209)
Chemistry
UTME / JAMB 1992
Reaction Rates & Chemical Equilibrium
Solution
In what way is equilibrium constant for the forward reaction related to that of the reversed reaction?
A
The additional of the two is expected to be one
B
The product of the two is expected to be one
C
The two equilibrium constants are identical
D
The product of the two is always greater than one
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
The equilibrium constant for a forward reaction is equal to the reciprocal of the equilibrium constant for the reversed reaction. therefore, the Kc for the forward reaction is related to the Kc for the reversed reaction. when the product of both (Kc)s is equal to one.
Source: Myschool Past Questions Archive (Record #13212)
Chemistry
UTME / JAMB 1992
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which of the following equilibria shows little or no net reaction when the volume of the system is decreased?
A
H2(g) + I2(g) ≈ 2HI(g)
B
2NO2(g) ≈ N2O4(g)+O4(g)N2O4(g)
C
PCI5(g) ≈ PCI3(g) + CI2(g)
D
ZnO(s) + CO2(g) ≈ ZnCO3(g)
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Simply calculate the number of moles on both reactants side and products side, for each of the options. The one that has equal number of moles on both sides, shows little or no reaction when volume is decreased. That is according to Le chatelier's principle.
Based on the above, option A is the correct answer, with 2 moles each on both sides.
Source: Myschool Past Questions Archive (Record #13215)
Chemistry
UTME / JAMB 1992
Reaction Rates & Chemical Equilibrium
For a general equation of the nature xP + yQ ≈ mR + nS, the expression for the equilibrium constant is?
A
k (p)x (Q)y
B
(p)x (Q)y / (R)m (S)n
C
(R)m (S)n / (p)x (Q)y
D
m(R) n (S) / x(P) y (Q)
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 #13218)
Chemistry
UTME / JAMB 1992
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which of these statements is TRUE about carbon (IV) oxide?
A
it supports combustion
B
It is strongly acidic in water
C
It is very soluble in water
D
It supports the buring of magnesium to produce magnesium oxide
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Carbon(iv)oxide does not burn, nor support the combustion of most substance .
The intense heat produced by burning magnesium,
However, decomposes Carbon(iv)oxide to release oxygen for the further oxidation of magnesium.
Carbon(iv)oxide dissolves in water to form trioxocarbonate(iv) acid ( soda water).
Source: Myschool Past Questions Archive (Record #13219)
Chemistry
UTME / JAMB 1992
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
Which of the following combination of gases is used for metal welding? i. Oxygen and ethyne, ii. Hydrogen and ethyne, iii. Hydrogen and oxygen, iv. Ethyne, hydrogen and oxygen.
A
i and ii
B
ii and iv
C
i and iii
D
ii and iv
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Oxyhydrogen is a mixture of hydrogen and oxygen gases.
This gaseous mixture is used for torches to process refractory materials and was the first gaseous mixture used for welding.
A gas torch that burns a mixture of acetylene and oxygen to produce a high-temperature flame (3,000^\circC or 5,400^\circF) that can weld or cut metal.
Source: Myschool Past Questions Archive (Record #13221)
Chemistry
UTME / JAMB 1992
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following oxides of nitrogen is unstable in air?
A
NO2
B
NO
C
N2O4
D
N2O5-
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 #13222)
Chemistry
UTME / JAMB 1992
Non-Metals & Their Compounds
Solution
The gas formed when ammonium trioxonitrate (V) is heated with sodium hydroxide is?
A
hydrogen
B
nitrogen (IV) oxide
C
oxygen
D
ammonia
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
When ammonium trioxonitrate (V) (NH₄NO₃) is heated with sodium hydroxide (NaOH), ammonia gas (NH₃) is released, along with water and sodium nitrate. The reaction can be represented as:
NH₄NO₃ + NaOH → NH₃ + H₂O + NaNO\(_3\)
Source: Myschool Past Questions Archive (Record #13224)