JAMB Chemistry 1993 past questions and answers

The dissolution of common salt in water is a physical change because

1. A.the salt can be obtained by crystallization
2. B.the salt can be recovered by the evaporation of the water
3. C.heat is not generated during mixing
4. D.the solution will not boil at 100°C

Which of the following substances is a mixture?

1. A.Sulphur powder
2. B.Bronze
3. C.Distilled water
4. D.Ethanol

How many moles of oxygen molecules would be produced from the decomposition of 2.5 moles of potassium trioxochlorate (V)?

1. A.2.50
2. B.3.50
3. C.3.75
4. D.7.50

A balanced chemical equation obeys the law of

1. A.conservation of mass
2. B.definite proportions
3. C.multiple proportions
4. D.conservation of energy

At 25°C and 1 atm, a gas occupies a volume of 1.50 dm³. What volume will it occupy at 100°C and 1 atm?

1. A.1.88 dm³
2. B.6.00 dm³
3. C.18.80 dm³
4. D.60.00 dm³

A gaseous mixture of 80.0 g of oxygen and 56.0 g of nitrogen has a total pressure of 1.8 atm. The partial pressure of oxygen in the mixture is [O = 16, N = 14]

1. A.0.8 atm
2. B.1.0 atm
3. C.1.2 atm
4. D.1.4 atm

For iodine crystals to sublime on heating, the molecules must acquire energy that is

1. A.less than the forces of attraction in the solid
2. B.equal to the forces of attraction in the solid
3. C.necessary to melt the solid
4. D.greater than the forces of attraction in both the solid and the liquid phases

An element, E, has the electronic configuration 1s²2s²2p⁶3s²3p³. The reaction of E with a halogen X can give

1. A.EX₃ and EX₅
2. B.EX₃ only
3. C.EX₅ only
4. D.EX₂ and EX₃

Two atoms represented as U and U are

1. A.isomers
2. B.allotropes
3. C.isotopes
4. D.anomers

As the difference in electronegativity between bonded atoms increases, polarity of the bond

1. A.decreases
2. B.increases
3. C.remains unchanged
4. D.reduces to zero

Which group of elements forms hydrides that are pyramidal in structure?

1. A.III
2. B.IV
3. C.V
4. D.VI

Water has a rather high boiling point despite its low molecular mass because of the presence of

1. A.hydrogen bonding
2. B.covalent bonding
3. C.ionic bonding
4. D.metallic bonding

The air around a petroleum refinery is most likely to contain

1. A.CO₂, SO₃ and N₂O
2. B.CO₂, CO and N₂O
3. C.SO₂, CO and NO₂
4. D.PH₃, H₂O and CO₂

Water can be identified by the use of

1. A.anhydrous copper (II) tetraoxosulphate (VI)
2. B.anhydrous sodium trioxocarbonate (IV)
3. C.potassium heptaoxochromate (VII)
4. D.copper (II) trioxocarbonate (IV)

The phenomenon whereby sodium trioxocarbonate (IV) decahydrate loses some of its water of crystallization on exposure to the atmosphere is known as

1. A.deliquescence
2. B.hygroscopy
3. C.effervescence
4. D.efflorescence

A student prepares 0.5 M solution each of hydrochloric and ethanoic acids and then measured their pH. The result would show that the

1. A.pH values are equal
2. B.HCl solution has a higher pH
3. C.sum of the pH values is 14
4. D.ethanoic acid solution has a higher pH

For which salt in the graph above does the solubility increase most rapidly with rise in temperature?

1. A.CaSO₄
2. B.KNO₃
3. C.NaCl
4. D.KCl

NH₃ + H₃O⁺ → NH₄⁺ + H₂O. It may be deduced from the reaction above that

1. A.a redox reaction has occurred
2. B.H₃O⁺ acts as an oxidizing agent
3. C.H₃O⁺ acts as an acid
4. D.water acts as an acid

4.0 g of sodium hydroxide in 250 cm³ of solution contains

1. A.0.40 moles per dm³
2. B.0.10 moles per dm³
3. C.0.04 moles per dm³
4. D.0.02 moles per dm³

During the electrolysis of a salt of a metal M, a current of 0.5 A flows for 32 minutes 10 seconds and deposits 0.325 g of M. What is the charge of the metal ion? [M = 65, 1F = 96,500 C per mole of electron]

1. A.1
2. B.2
3. C.3
4. D.4

Which of the following reactions occurs at the anode during the electrolysis of a very dilute aqueous solution of sodium chloride?

1. A.OH⁻ − e → OH
2. B.Cl⁻ − e⁻ → Cl
3. C.OH⁻ + Cl⁻ → HCl + O²⁻
4. D.Na⁺ − e⁻ → Na/Hg amalgam (over Hg)

Half-cell reactions and E° values:
Cu²⁺(aq) + 2e⁻ → Cu(s): +0.34 V
Fe²⁺(aq) + 2e⁻ → Fe(s): −0.44 V
Ba²⁺(aq) + 2e⁻ → Ba(s): −2.90 V
Zn²⁺(aq) + 2e⁻ → Zn(s): −0.76 V
From the data above, it can be deduced that the most powerful reducing agent of the four metals is

1. A.Cu
2. B.Fe
3. C.Ba
4. D.Zn

The oxidation states of chlorine in HOCl, HClO₃ and HClO₄ are respectively

1. A.-1, +5 and +7
2. B.-1, +5 and 7
3. C.+1, +3 and +4
4. D.+1, +5 and +7

A reaction takes place spontaneously if

1. A.ΔG = O
2. B.ΔS < O and ΔH > O
3. C.ΔH < TΔS
4. D.ΔG > O

The standard enthalpies of formation of CO_2(g), H₂O_(g) and CO_(g) in kJ mol⁻¹ are −394, −242 and −110 respectively. What is the standard enthalpy change for the reaction CO_(g) + H₂O_(g) → CO_2(g) + H_2(g)?

1. A.−42 kJ mol⁻¹
2. B.+42 kJ mol⁻¹
3. C.−262 kJ mol⁻¹
4. D.+262 kJ mol⁻¹

10 g of a solid is in equilibrium with its own vapour. When 1 g of a small amount of solid is added, the vapour pressure

1. A.remains the same
2. B.drops
3. C.increases by 1%
4. D.increases by 99%

In the diagram above, curve X represents the energy profile for a homogeneous gaseous reaction. Which of the following conditions would produce curve Y for the same reaction?

1. A.Increase in temperature
2. B.Increase in the concentration of a reactant
3. C.Addition of a catalyst
4. D.Increase in pressure

NaCl_(s) + H₂SO_4(l) → HCl_(g) + NaHSO_4(s). In the reaction above, H₂SO₄ behaves as

1. A.a strong acid
2. B.an oxidizing agent
3. C.a good solvent
4. D.a dehydrating agent

Which of these gases can be dried with concentrated H₂SO₄?

1. A.HBr
2. B.H₂S
3. C.NH₃
4. D.SO₂

Which of these salts will produce its metal, oxygen and nitrogen (IV) oxide on heating?

1. A.Silver trioxonitrate (V)
2. B.Sodium trioxonitrate (V)
3. C.Calcium trioxonitrate (V)
4. D.Lithium trioxonitrate (V)

An experiment produces a gaseous mixture of carbon (IV) oxide and carbon (II) oxide. In order to obtain pure carbon (II) oxide, the gas mixture should be

1. A.passed over heated copper (II) oxide
2. B.bubbled through concentrated tetraoxosulphate (VI) acid
3. C.bubbled through sodium hydroxide solution
4. D.bubbled through water

Which of the following is a property of ionic chlorides?

1. A.They can be decomposed by heat
2. B.They react with aqueous AgNO₃ to give a white precipitate which is soluble in excess ammonia
3. C.They explode when in contact with dry ammonia gas
4. D.They react with concentrated tetraoxosulphate (VI) acid to give white fumes of chlorine gas

When dilute aqueous solutions of lead (II) nitrate and potassium bromide are mixed, a precipitate is observed. The products of this reaction are

1. A.PbO_(s) + Br⁻_(aq) + KNO₃
2. B.Br₂ + NO_2(g) + PbBr_2(s)
3. C.PbO_(s) + K⁺_(aq) + Br⁻_(aq) + NO_2(g)
4. D.PbBr_2(s) + K⁺_(aq) + NO₃⁻_(aq)

Bronze is an alloy of

1. A.silver and copper
2. B.silver and gold
3. C.copper and nickel
4. D.copper and zinc
5. E.copper and tin

Copper metal will react with concentrated trioxonitrate (V) acid to give

1. A.Cu(NO₃)₂ + NO + N₂O₄ + H₂O
2. B.Cu(NO₃)₂ + NO + H₂O
3. C.CuO + NO₂ + H₂O
4. D.Cu(NO₃)₂ + NO₂ + H₂O

The active reducing agent in the blast furnace for the extraction of iron is

1. A.carbon
2. B.limestone
3. C.carbon (II) oxide
4. D.calcium oxide

Al₂O_3(s) + 3H₂SO_4(aq) → Al₂(SO₄)_3(aq) + 3H₂O_(l)
Al₂O_3(s) + 2NaOH_(aq) + 3H₂O_(l) → 2NaAl(OH)_4(aq)
We can conclude from the equations above that Al₂O₃ is

1. A.an acidic oxide
2. B.an amphoteric oxide
3. C.a basic oxide
4. D.a neutral oxide

H₂N—CH₂—COOH
The two functional groups in the above compound are

1. A.alcohol and amine
2. B.acid and amine
3. C.aldehyde and acid
4. D.ketone and amine

The fraction of crude oil used as jet fuel is

1. A.refinery gas
2. B.diesel oil
3. C.kerosene
4. D.gasoline

CH₃CH(CH₃)CH₂CH(CH₃)CH₂CH₃
The IUPAC nomenclature for the compound above is

1. A.dimethylhexane
2. B.3,5 dimethylhexane
3. C.1,1 dimethyl, 3 methylpentane
4. D.2,4 dimethylhexane

It is not desirable to use lead tetraethyl as an anti-knock agent because

1. A.it is expensive
2. B.of pollution effects from the exhaust fumes
3. C.it lowers the octane rating of petrol
4. D.it is explosive

The carbon atoms on ethane are

1. A.sp² hybridized
2. B.sp³ hybridized
3. C.sp²d hybridized
4. D.sp hybridized

Catalytic hydrogenation of benzene produces

1. A.an aromatic hydrocarbon
2. B.margarine
3. C.cyclohexane
4. D.D.D.T.

CH₃COOCH₂CH₃ and CH₃CH₂CH₂COOH are

1. A.isomers
2. B.esters
3. C.carboxylic acids
4. D.polymers

Palm wine turns sour with time because

1. A.the sugar content is converted into alcohol
2. B.the carbon (IV) oxide formed during the fermentation process has a sour taste
3. C.it is commonly adulterated by the tappers and sellers
4. D.microbial activity results in the production of organic acids within it

The function of the copper (II) tetraoxosulphate (VI) in dilute H₂SO₄ in the figure above is to

1. A.dry the gas
2. B.absorb phosphine impurity
3. C.absorb ethene impurity
4. D.form an acetylide with ethyne

Which of the following represents saponification?

1. A.Reaction of carboxylic acids with sodium hydroxide
2. B.Reaction of alkanoates with acid
3. C.Reaction of carboxylic acids with alcohols
4. D.Reaction of alkanoates with sodium hydroxide

The confirmatory test for alkanoic acids in organic qualitative analysis is the

1. A.turning of wet blue litmus paper red
2. B.reaction with alkanols to form esters
3. C.reaction with sodium hydroxide to form salt and water
4. D.reaction with aqueous Na₂CO₃ to liberate a gas which turns lime water milky