JAMB Chemistry 1987 past questions and answers

A brand of ink containing cobalt (II), copper (II) and iron (II) ions can best be separated into its various components by

1. A.fractional crystallization
2. B.fractional distillation
3. C.sublimation
4. D.chromatography

Which of the following substances is a mixture?

1. A.Granulated sugar
2. B.Sea-water
3. C.Sodium chloride
4. D.Iron filings

The number of molecules of carbon (IV) oxide produced when 10.0 g of CaCO₃ is treated with 0.2 dm³ of 1 M HCl in the equation CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂ is [Ca = 40, O = 16, C = 12, N_A = 6.02 × 10²³, H = 1, Cl = 35.5]

1. A.1.00 × 10²³
2. B.6.02 × 10²³
3. C.6.02 × 10²²
4. D.6.02 × 10²⁴

In the reaction CaC_2(s) + 2H₂O_(l) → Ca(OH)_2(s) + C₂H_2(g) what is the mass of solid calcium carbide needed to produce 1000 cm³ of acetylene gas at S.T.P.? [C = 12, Ca = 40, G.M.V = 22400 cm³]

1. A.3.8 g
2. B.2.9 g
3. C.2.0 g
4. D.1.0 g

If the quantity of oxygen occupying a 2.76 litre container at a pressure of 0.825 atmospheres and 300 K is reduced by one-half, what is the pressure exerted by the remaining gas?

1. A.1.650 atm
2. B.0.825 atm
3. C.0.413 atm
4. D.0.275 atm

Which of the following substances has the lowest vapour density? [O = 16, Cl = 35.5, H = 1, C = 12]

1. A.Ethanoic acid
2. B.Propanol
3. C.Dichloromethane
4. D.Ethanal

If d represents the density of a gas and K is a constant, the rate of gaseous diffusion r is related to d by the equation

1. A.r = k/√d
2. B.r = kd
3. C.r = k/d
4. D.r = k√d

An isotope has an atomic number of 17 and a mass number of 36. Which of the following gives the correct number of neutrons and protons in an atom of the isotope?

1. A.Neutrons 53, Protons 17
2. B.Neutrons 17, Protons 36
3. C.Neutrons 19, Protons 17
4. D.Neutrons 36, Protons 17

The atomic numbers of two elements X and Y are 12 and 16 respectively. The bond in the compound formed between the atoms of these two elements is

1. A.ionic
2. B.covalent
3. C.neutral
4. D.co-ordinate

An element Z, contained 90% of ¹⁶₈Z and 10% of ¹⁸₈Z. Its relative atomic mass is

1. A.16.0
2. B.16.2
3. C.17.0
4. D.17.8

The greater the difference in electronegativity between bonded atoms, the

1. A.lower the polarity of the bond
2. B.higher the polarity of the bond
3. C.weaker the bond
4. D.higher the possibility of the substance formed being a molecule.

A stream of air was successively passed through three tubes X, Y and Z containing a concentrated aqueous solution of KOH, red hot copper powder and fused calcium chloride respectively. What was the composition of the gas emanating from tube Z?

1. A.CO₂ and the inert gases
2. B.N₂, CO₂ and the inert gases
3. C.N₂ and the inert gases
4. D.water vapour, N₂ and the inert gases.

In the purification of town water supply, alum is used principally to

1. A.kill bacteria
2. B.control the pH of water
3. C.improve the taste of the water
4. D.coagulate small particles of mud.

Which of the following water samples will have the highest titre value when titrated for the Ca²⁺ ions using soap solution?

1. A.Permanently hard water after boiling
2. B.Temporarily hard water after boiling
3. C.Rain water stored in a glass jar for two years
4. D.Permanently hard water passed through permutit.

Oil spillage in ponds and creeks can be cleaned up by

1. A.burning off the oil layer
2. B.spraying with detergent
3. C.dispersal with compressed air
4. D.spraying with hot water.

The solubility of Na₃AsO₄(H₂O)₁₂ is 38.9 g per 100 g H₂O. What is the mass percentage of Na₃AsO₄ in the saturated solution? [As = 75, Na = 23, O = 16, H = 1]

1. A.87.2%
2. B.38.9%
3. C.19.1%
4. D.13.7%

Which is the correct set of results for tests conducted respectively on fresh lime juice and ethanol?

1. A.Add crystals of NaHCO₃: fresh lime juice, gas evolved; ethanol, no gas evolved
2. B.Test with methyl orange: fresh lime juice, turns colourless; ethanol, no change
3. C.Taste: fresh lime juice, bitter; ethanol, sour
4. D.Add a piece of sodium: fresh lime juice, no gas evolved; ethanol, hydrogen evolved

In which of the following are the aqueous solutions of each of the substances correctly arranged in order of decreasing acidity?

1. A.Ethanoic acid, milk of magnesia, sodium chloride, hydrochloric acid and sodium hydroxide
2. B.Ethanoic acid, hydrochloric acid, milk of magnesia, sodium chloride and sodium hydroxide
3. C.Hydrochloric acid, ethanoic acid, sodium chloride, milk of magnesia and sodium hydroxide
4. D.Hydrochloric acid, sodium hydroxide, sodium chloride, ethanoic acid and milk of magnesia.

The basicity of tetraoxophosphate (V) acid is

1. A.7
2. B.5
3. C.4
4. D.3

If 24.83 cm³ of 0.15 M NaOH is titrated to its end point with 39.45 cm³ of HCl, what is the molarity of the HCl?

1. A.0.094 M
2. B.0.150 M
3. C.0.940 M
4. D.1.500 M

A quantity of electricity liberates 3.6 g of silver from its salt. What mass of aluminium will be liberated from its salt by the same quantity of electricity? [Al = 27, Ag = 108]

1. A.2.7 g
2. B.1.2 g
3. C.0.9 g
4. D.0.3 g

Which of the following statements is CORRECT if 1 Faraday of electricity is passed through 1 M CuSO₄ solution for 1 minute?

1. A.The pH of the solution at the cathode decreases
2. B.The pH of the solution at the anode decreases
3. C.1 mole of Cu will be liberated at the cathode
4. D.60 moles of Cu will be liberated at the anode.

What mass of magnesium would be obtained by passing a current of 2 amperes for 2 hrs. 30 mins through molten magnesium chloride? [1 Faraday = 96500 coulombs, Mg = 24]

1. A.1.12 g
2. B.2.00 g
3. C.2.24 g
4. D.4.48 g

In the reaction: 3CuO + 2NH₃ → 3Cu + 3H₂O + N₂ how many electrons are transferred for each mole of copper produced?

1. A.4.0 × 10⁻²³
2. B.3.0 × 10⁻²³
3. C.1.2 × 10²⁴
4. D.6.0 × 10²⁴

Z is a solid substance which liberates carbon (IV) oxide on treatment with concentrated H₂SO₄. A warm solution of Z also decolorizes acidified KMnO₄. The solid substance, Z, is

1. A.sodium hydrogen trioxocarbonate (IV)
2. B.methanoic acid
3. C.iron (II) trioxocarbonate (IV)
4. D.ethanedioic acid (oxalic acid).

5 g of ammonium trioxonitrate (V) on dissolution in water cooled its surrounding water and container by 1.6 kJ. What is the heat of solution of NH₄NO₃? [N = 14, O = 16, H = 1]

1. A.+51.4 kJ mol⁻¹
2. B.+25.6 kJ mol⁻¹
3. C.+12.9 kJ mol⁻¹
4. D.−6.4 kJ mol⁻¹

Tetraoxosulphate (VI) acid is prepared using the chemical reaction SO_3(g) + H₂O_(l) → H₂SO_4(l). Given the heats of formation for SO_3(g), H₂O_(l) and H₂SO_4(l) as −395 kJ mol⁻¹, −286 kJ mol⁻¹ and −811 kJ mol⁻¹ respectively, the enthalpy change accompanying this reaction is

1. A.−1032 kJ
2. B.−130 kJ
3. C.+130 kJ
4. D.+1032 kJ

The times taken for iodine to be liberated in the reaction between sodium thiosulphate and hydrochloric acid at various temperature are as follows:
Temp °C: 25, 35, 45
Time (seconds): 72, 36, 18
These results suggest that

1. A.for a 10° rise in temperature, rate of reaction is doubled
2. B.for a 10° rise in temperature, rate of reaction is halved
3. C.time taken for iodine to appear does not depend on temperature
4. D.for a 10° rise in temperature, rate of reaction is tripled.

The reaction between sulphur (IV) oxide and oxygen is represented by the equilibrium reaction 2SO_2(g) + O_2(g) ⇌ 2SO_3(g), ΔH = −196 kJ. What factor would influence increased production of SO_3(g)?

1. A.Addition of a suitable catalyst
2. B.Increase in the temperature of the reaction
3. C.Decrease in the temperature of the reaction
4. D.Decrease in the concentration of SO_2(g).

Which of the following equations correctly represents the action of hot concentrated alkaline solution on chlorine?

1. A.Cl_2(g) + 2OH⁻_(aq) → OCl⁻_(aq) + Cl⁻_(aq) + H₂O_(l)
2. B.3Cl_2(g) + 6OH⁻_(aq) → ClO₃⁻_(aq) + 5Cl⁻_(aq) + 3H₂O_(l)
3. C.3Cl_2(g) + 6OH⁻_(aq) → ClO₃⁻_(s) + 5Cl⁻_(aq) + 3H₂O_(l)
4. D.3Cl_2(g) + 6OH⁻_(aq) → 5ClO₃⁻_(aq) + Cl⁻_(aq) + 3H₂O_(l)

Magnesium ribbon was allowed to burn inside a given gas P leaving a white solid residue Q. Addition of water to Q liberated a gas which produced dense white fumes with a drop of hydrochloric acid. The gas P was

1. A.nitrogen
2. B.chlorine
3. C.oxygen
4. D.sulphur (IV) oxide

The best treatment for a student who accidentally poured concentrated tetraoxosulphate (VI) acid on his skin in the laboratory is to wash the skin with

1. A.cold water
2. B.sodium hydroxide solution
3. C.iodine solution
4. D.sodium trioxocarbonate (IV) solution.

In which of the following pairs of elements is allotropy exhibited by each element?

1. A.Phosphorus and hydrogen
2. B.Oxygen and chlorine
3. C.Sulphur and nitrogen
4. D.Oxygen and sulphur

Which of the following gases can best be used for demonstrating the fountain experiment?
(i) Nitrogen (ii) Ammonia (iii) Nitrogen (I) oxide (iv) Hydrogen chloride

1. A.(ii) and (iii)
2. B.(i) and (iii)
3. C.(ii) and (iv)
4. D.(ii) only.

When calcium hydroxide is heated with ammonium tetraoxosulphate (VI), the gas given off may be collected by

1. A.bubbling it through concentrated H₂SO₄
2. B.bubbling it through water and then passing it through calcium oxide
3. C.passing it directly through calcium oxide
4. D.passing it directly through calcium chloride.

Which of the following elements will form oxide which will dissolve both in dilute HNO₃ and NaOH solutions to form salts?

1. A.Al
2. B.Mg
3. C.Ag
4. D.Mn

Alloys are best prepared by

1. A.high temperature welding of the metals
2. B.electrolysis using the major metallic component as cathode
3. C.reducing a mixture of the oxides of the elements
4. D.cooling a molten mixture of the necessary elements.

Corrosion is exhibited by

1. A.iron only
2. B.electropositive metals
3. C.metals below hydrogen in the electrochemical series
4. D.all metals.

Inspite of the electronic configuration, 1s²2s²2p², carbon is tetravalent because

1. A.the electrons in both 2s and 2p orbitals have equal energy
2. B.the electrons in both 2s and 2p orbitals are equivalent
3. C.both the 2s and 2p orbitals hydrodize
4. D.the six orbitals hybridize to four.

Which of the following compounds will give a precipitate with an aqueous ammoniacal solution of copper (I) chloride?

1. A.CH₃CH = CHCH₃
2. B.CH₃C ≡ CCH₃
3. C.HC ≡ C–CH₂CH₃
4. D.CH₂ = CH–CH = CH₂

The efficiency of petrol as a fuel in high-compression internal combustion engines improves with an increase in the amount of

1. A.branched chain alkanes
2. B.straight chain alkanes
3. C.cycloalkanes
4. D.halogenated hydrocarbons

A palm wine seller stoppered a bottle of his palm wine in his stall and after a few hours the bottle exploded. Which of the following equations represents the reaction that occurred?

1. A.C₆H₁₂O₆ → 2C₂H₅OH + 2CO_2(g) (enzymes)
2. B.C₂H₅OH → CH₂ = CH_2(g) + H₂O
3. C.C₂H₅OH + dil H₂SO₄ → C₂H₅OSO₂OH
4. D.2C₆H₁₂O₆ → C₁₂H₂₂O₁₃ + H₂O.

Ethanol reacts with aqueous sodium mono-oxoiodate (I) to give a bright yellow solid with a characteristic smell. The product is

1. A.trichloromethane
2. B.triiodomethane
3. C.iodoethane
4. D.ethanal.

The most volatile fraction obtained from fractional distillation of crude petroleum contains

1. A.butane, propane and kerosene
2. B.butane, propane and petrol
3. C.ethane, methane and benzene
4. D.methane, ethane and propane.

Local black soap is made by boiling palm oil with liquid extract of ash. The function of the ash is to provide the

1. A.acid
2. B.ester of alkanoic acid
3. C.alkali
4. D.alkanol

Synthetic rubber is made by polymerization of

1. A.2 methyl buta – 1, 3 – diene
2. B.2 methyl buta – 1,2– diene
3. C.2 methyl but–1–ene
4. D.2 methyl but–2–ene

Complete oxidation of propan –1–ol gives

1. A.propanal
2. B.propan–2–al
3. C.propan–1–one
4. D.propanoic acid

When water drops are added to calcium carbide in a container and the gas produced is passed through a jet and lighted, the resultant flame is called an

1. A.oxyethylene flame
2. B.oxyhydrocarbon flame
3. C.oxyacetylene flame
4. D.oxymethane flame

The structure of benzoic acid is

1. A.Benzene ring with –CHO (structure A in the figure)
2. B.Cyclohexane ring with –COOH (structure B in the figure)
3. C.Benzene ring with –CH₂–COOH (structure C in the figure)
4. D.Benzene ring with –COOH (structure D in the figure)