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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)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
Solution
Which of these gases can be dried with concentrated H2SO4?
A
HBr
B
H2S
C
NH3
D
SO2
medium Difficulty
Verified Correct Answer: Option D
Chemical Principles & Mechanism
In the preparation of \(SO_{2}\), we have the resultant reaction from heating the mixture of \(Na_{2}SO_{3}\) and \(HCl\) as:
\(Na_{2}SO_{{3}{(aq)}} + 2HCl_{(aq)} \to 2NaCl_{(aq)} + H_{2}O_{(l)} + SO_{{2}{(g)}}\)
Passing the gas evolved through conc. \(H_{2}SO_{4}\), we collect \(SO_{2}\) by DOWNWARD DELIVERY, leaving \(NaCl\) in the flask.
Source: Myschool Past Questions Archive (Record #13421)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
Which of these salts will produce its metal, oxygen and nitrogen (IV) oxide on heating?
A
Silver and trioxonitrate (V)
B
Sodium trioxonitrate (V)
C
Calcium trioxonitrate (V)
D
Lithium trioxonitrate (V)
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 #13422)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
An experiment produces a gaseous mixtures of carbon (IV) oxide and carbon (II) oxide. In order to obtain pure carbon (II) oxide, the gas mixture should be?
A
passed over heated copper (II) oxide
B
bubbled through concentrated tetraoxosulphate (IV) acid
C
bubbled through sodium hydroxide solution
D
bubbled through water
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 #13425)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
Which of the following is a property of ionic chlorides?
A
They can be decomposed by heat
B
They react with aqueous AgNO3 to give a white precipiate which is soluble in excess ammonia
C
They explode when in contact with dry ammonia
D
They react with concentrated tetraoxosulphate (IV) acid to give white fumes of chlorine gas
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 #13432)
Chemistry
UTME / JAMB 1993
Stoichiometry, Mole Concept & Volumetric Analysis
When dilute aqueous solutions of lead (II) nitrate and potassium bromide are mixed, a precipitate is observed.
The products of this reaction are?
A
PbO(s) + Br- + KNO3
B
Br2 + NO2(g) + PbBr2(s)
C
PbO(s) + K+(aq) + Br(aq) + NO2(g)
D
PbBr2(s) + K(aq) + K+(aq) + NO3(aq)
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 #13437)
Chemistry
UTME / JAMB 1993
Metals, Transition Elements & Extraction
Solution
Bronze is an alloy of?
A
silver and copper
B
silver and gold
C
copper and nickle
D
copper and zinc
E
copper and tin
medium Difficulty
Verified Correct Answer: Option E
Chemical Principles & Mechanism
Bronze is an alloy of copper and tin.
Source: Myschool Past Questions Archive (Record #13445)
Chemistry
UTME / JAMB 1993
Oxidation, Reduction & Redox Reactions
The active reducing agent in the blast furnace for the extraction of iron is?
A
carbon
B
limestone
C
carbon(II)oxide
D
calcium oxide
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 #13448)