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Chemistry
UTME / JAMB 1993
Periodic Table & Periodicity
Solution
Which group of elements forms hydrides that are pyramidal in structure?
A
III
B
IV
C
V
D
VI
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Group V elements (also known as pnictogens) form hydrides that are pyramidal in structure. The trihydrides, such as NH\(_3\) (ammonia), PH\(_3\) (phosphine), AsH\(_3\) (arsine), and SbH\(_3\) (stibine), all exhibit a pyramidal shape.
Source: Myschool Past Questions Archive (Record #13309)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
Water has a rather high boiling point despite its low molecular mass because of the presence of?
A
hydrogen bonding
B
covalent bonding
C
ionic bonding
D
metallic bonding
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 #13310)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Argon is used in gas-filled electric lamp because it helps to?
A
prevent the reduction of the lamp fillaments
B
prevent oxidation of the lamp fillaments
C
make the lamp fillament glow brightly
D
keep the atmosphere in the lamp inert
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Argon is used to fill incandescent and fluorescent light bulbs to prevent oxygen from corroding the hot filament.
Source: Myschool Past Questions Archive (Record #13311)
Chemistry
UTME / JAMB 1993
Organic Chemistry I: Hydrocarbons & Crude Oil
Solution
The air around a petroleum refinery is most likely to contain?
A
CO2, SO3 and N2O
B
CO2, CO and N2O
C
SO2, CO and NO2
D
PH3 H2O and CO2
medium Difficulty
Verified Correct Answer: Option C
Chemical Principles & Mechanism
Topic is Impurities of Crude-oil
Source: Myschool Past Questions Archive (Record #13312)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Water can be identified by the use of?
A
anhydrous copper (II) tetraoxosulphate (VI)
B
anhydrous sodium trioxocarbonate (IV)
C
potassium heptaoxochromate (VII)
D
copper (II) trioxocaronate (IV)
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Anhydrous CuSO4 will turn blue with water
Source: Myschool Past Questions Archive (Record #13326)
Chemistry
UTME / JAMB 1993
Water, Solutions & Solubility
Solution
The phenomenon whereby sodium trioxocarbonate (IV) decahydrate loses some of its water of crystallization on exposure to the atmosphere is known as?
A
deliquescene
B
hygroscopy
C
effervescence
D
efflorescence
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
Topic is Salts With Water of Crystallization.
Source: Myschool Past Questions Archive (Record #13328)
Chemistry
UTME / JAMB 1993
Acids, Bases, pH & Salts
Solution
A student prepares 0.5 M solution each of hydrochloric and ethanoic acids and then measured pH. The result would show that the?
A
pH values are equal
B
HCI solution has a higher pH
C
sum of the values is 14
D
ethanoic acid solution has a higher pH
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
A weak acid would have a higher pH value than a strong acid at the same concentration. Strong acids dissociate completely in water, releasing more hydrogen ions (H\(^+\) and thus having a lower pH (more acidic). Weak acids only partially dissociate, resulting in fewer H\(^+\) ions and a higher pH (less acidic).
HCl is a strong acid because it dissociates completely when dissolved in water, thereby releasing more hydrogen ions and thus having a lower pH value when compared to ethanoic acid, a weak acid which dissociates partially when dissolved in water, thereby releasing less hydrogen ions, invariably having a higher pH, regardless of the fact that both acids have the same concentration of 0.5M.
Source: Myschool Past Questions Archive (Record #13331)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
4.0 g of sodium hydroxide in 250 cm3 of solution contains?
A
0.40 moles per dm3
B
0.10 moles per dm3
C
0.04 moles per dm3
D
0.02 moles per dm3
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Unit of concentration = (moles)/(dm3)
If 250 cm3 solution NaOH contains 4.0 g NaOH
i.e -1cm3 solution NaOH (4.0)/(250) g
∴ 1000 cm3 (1 dm3) will contain (40 x 1000) / (250 x 1) = 16 g/dm3
16 g/dm3 = 16g/dm3 + molar mass NaOH
because no of moles = (mass of substance given) / (molar mass)
∴ (16 g) / (40 g) dm3 = (16 g)/(dm3 x (1 mole)/ (40g) = 0.4 (moles)/(dm3)
Source: Myschool Past Questions Archive (Record #13363)
Chemistry
UTME / JAMB 1993
Electrolysis & Electrochemical Cells
Solution
During the electrolysis of a salt of a metal M, a current of 0.5 A flows from for 32 minutes 10 seconds and deposits 0.325 g of M, What is the charge of the metal ion?
(M = 65, If = 96,500 C per mole of electron)
A
1
B
2
C
3
D
4
medium Difficulty
Verified Correct Answer: Option B
Chemical Principles & Mechanism
Ampere = (Coulomb) x (Sec) x 1930 secs = 965 coulombs (unit of current)
But quantity of electricity = current x time = (Coulomb)/(Sec) x time
If 0.5 A for 32 mins 10 secs; Quantity of electricity = (0.5 coulomb)/(Sec x 1930) secs
= 965 coulombs
Since 965 coulombs give 0.325 g M
i.e1 coulombs = (0.325)/(965) g
∴96500 coulombs = (0.30)/(965) x 96500 =32.5 g
∴(65 g)/(32.5) = 2
inference: it takes 2 Faraday of electricity to deposit 1 mole of M. Therefore, the change on M ion = 2.
Source: Myschool Past Questions Archive (Record #13378)
Chemistry
UTME / JAMB 1993
Electrolysis & Electrochemical Cells
Which of the reactions occurs at the anode during the electrolysis of a very dilute aqueous solution of sodium chloride?
A
OH- - e → OH
B
CIsup>- - e → CI
C
OHsup>- + CIsup>-HCI + O2
D
Na+ - esup>- Hg (Na)/(Hg) amalgam
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 #13388)
Chemistry
UTME / JAMB 1993
Oxidation, Reduction & Redox Reactions
The oxidation states of chlorine in HOCL, HCLO3 and HCLO4 are respectively?
A
-1, +5, and +7
B
-1, -5 and 7
C
+1, +3 and +4
D
+1, +5 and +7
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 #13392)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
A reaction takes places spontaneously if?
A
∆G = O
B
∆S O
C
∆H < T ∆S
D
∆G > O
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 #13394)
Chemistry
UTME / JAMB 1993
Chemical Energetics & Thermochemistry
Solution
The standard enthalpies of formation of CO2(g), H2O(g) and CO(g) in kJ mol- are -394, -242 and -110 respectively. What is the standard enthalpy change for the reaction CO(g) + H2(g)O → CO2(g) + H2(g)?
A
-42 KJ mol-
B
+42 KJ mol-
C
-262 KJ mol-
D
+262 KJ mol-
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Standard enthalpy change of a process = ∆H° process = ∆H° F reactant - DF° products
Source: Myschool Past Questions Archive (Record #13399)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
10g of a solid is in equilibrium with its own vapour.
When 1 g of a small amount of solid is added, the vapour pressure?
A
remains the same
B
drops
C
increases by 1%
D
increases by 99%
medium Difficulty
Verified Correct Answer: Option A
Chemical Principles & Mechanism
Since the solid was at equilibrium with its own vapour, which means pressure is constant. However, if 1g of the solid was added, the pressure remains the same, since pressure of the system in equilibrium is not affected by solid.
Source: Myschool Past Questions Archive (Record #13419)
Chemistry
UTME / JAMB 1993
Acids, Bases, pH & Salts
NaCI(s) + H2SO4(I) → HCI(g) + NaHSO4(s).
In the reaction above, H2SO4 behaves as?
A
a strong acid
B
an oxidizing agent
C
a good solvent
D
a dehydrating agent
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 #13420)