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Instruction
JAMB Chemistry 1990
JAMB (UTME)
Chemistry
1990
Q8201.Alloys are best prepared by
Ahigh temperature arc welding of the metals
Belectrolysis using the major metallic component as cathode
Creducing a mixture of the oxides of the elements
Dcooling a molten mixture of the necessary elements
Correct Answer: D
Alloys are best prepared by melting the constituent metals together and then cooling the molten mixture.
JAMB (UTME)
Chemistry
1990
Q8202.Corrosion is exhibited by
Airon only
Belectropositive metals
Cmetals below hydrogen in the electrochemical series
Dall metals
Correct Answer: B
Corrosion is exhibited by electropositive metals (metals above hydrogen in the electrochemical series), which have a tendency to lose electrons and form compounds.
JAMB (UTME)
Chemistry
1990
Q8203.Inspite of the electronic configuration, 1s²2s²2p², carbon is tetravalent because
Athe electrons in both 2s and 2p orbitals have equal energy
Bthe electrons in both 2s and 2p orbitals are equivalent
Cboth the 2s and 2p orbitals hybridize
Dthe six orbitals hybridize to four
Correct Answer: C
In carbon, one 2s electron is promoted to a 2p orbital, and then the one 2s and three 2p orbitals hybridize to form four equivalent sp³ hybrid orbitals. This allows carbon to form four bonds (tetravalent).
JAMB (UTME)
Chemistry
1990
Q8204.Which of the following compounds will give a precipitate with an aqueous ammoniacal solution of copper (I) chloride?
ACH₃CH=CHCH₃
BCH₃C≡CH₃
CCH≡C-CH₂CH₃
DCH₂=CH-CH=CH₂
Correct Answer: C
Aqueous ammoniacal copper(I) chloride reacts with terminal alkynes (R-C≡CH) to form a red precipitate of copper(I) acetylide. CH≡C-CH₂CH₃ is a terminal alkyne.
JAMB (UTME)
Chemistry
1990
Q8205.The efficiency of petrol as a fuel in high compression internal combustion engines improves with an increase in the amount of
ABranched chain alkanes
BStraight chain alkanes
CCycloalkanes
DHalogenated hydrocarbons
Correct Answer: A
Branched chain alkanes have higher octane ratings and burn more efficiently in high compression engines than straight chain alkanes.
JAMB (UTME)
Chemistry
1990
Q8206.A palm wine seller stoppered a bottle of his palm wine in his stall and after a few hours the bottle represents the reaction that occurred?
AC₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
BC₂H₅OH → CH₂=CH₂(g) + H₂O
CC₂H₅OH + dil H₂SO₄ → C₂H₅OSO₃OH
D2C₆H₁₂O₆ → C₁₂H₂₂O₁₁ + H₂O
Correct Answer: A
The reaction is fermentation of sugar (glucose) by yeast to produce ethanol and carbon dioxide.
JAMB (UTME)
Chemistry
1990
Q8207.Ethanol reacts with aqueous sodium mono-oxoate (I) to give a bright yellow solid with a characteristic smell. The product is
Atrichloromethane
Biodoform
Cethanal
Dethanoic acid
Correct Answer: B
Ethanol reacts with sodium mono-oxoate(I) (sodium hypoiodite, NaOI) to form a yellow precipitate of iodoform (CHI₃), which has a characteristic smell.
JAMB (UTME)
Chemistry
1990
Q8208.The most volatile fraction obtained from fractional distillation of crude petroleum is
Abutane, propane and kerosene
Bbutane, propane and petrol
Cethane, methane and benzene
Dethane, methane and propane
Correct Answer: D
The most volatile fraction (lowest boiling point) is the refinery gas, which consists of ethane, methane, and propane.
JAMB (UTME)
Chemistry
1990
Q8209.Local black soap is made by boiling palm with liquid extract of ash. The function of the ash is to provide the
Aacid
Bester of alkanoic acid
Calkali
Dalkanol
Correct Answer: C
Ash contains potassium carbonate (potash), which is an alkali. It reacts with the fats/oils in palm to form soap (saponification).
JAMB (UTME)
Chemistry
1990
Q8210.Synthetic rubber is made by polymerization of
A2-methylbuta-1,3-diene
B2-methylbuta-1,2-diene
C2-methylbuta-1-ene
D2-methylbuta-2-ene
Correct Answer: A
Natural rubber is a polymer of 2-methylbuta-1,3-diene (isoprene). Synthetic rubber is also made from similar dienes.
JAMB (UTME)
Chemistry
1990
Q8211.Complete oxidation of propan-1-ol gives
Apropanal
Bpropan-2-ol
Cpropan-1-one
Dpropanoic acid
Correct Answer: D
Complete oxidation of a primary alkanol (propan-1-ol) gives an alkanoic acid (propanoic acid).
JAMB (UTME)
Chemistry
1990
Q8212.When water drops are added to calcium carbide in a container and the gas produced is passed through a jet and ignited, the flame produced is called
Aoxyethylene flame
Boxyhydrocarbon flame
Coxyacetylene flame
Doxymethane flame
Correct Answer: C
Calcium carbide reacts with water to produce acetylene (ethyne) gas. Burning acetylene in oxygen produces an oxy-acetylene flame.
JAMB (UTME)
Chemistry
1990
Q8213.The structure of benzoic acid is
AC₆H₅COOH
BC₆H₁₁COOH
CCH₃C₆H₄COOH
DC₆H₅CH₂COOH
Correct Answer: A
Benzoic acid is a carboxylic acid with a benzene ring directly attached to the carboxyl group: C₆H₅COOH.
Instruction
JAMB Chemistry 1991
JAMB (UTME)
Chemistry
1991
Q8214.Which of the following would support the conclusion that a solid sample is a mixture?
AThe solid can be ground to a fine powder
BThe density of the solid is 2.25 g dm⁻³
CThe solid has a melting range of 300°C to 375°C
DThe solid absorbs moisture from the atmosphere
Correct Answer: C
A pure solid has a sharp, definite melting point. A mixture melts over a range of temperatures.
JAMB (UTME)
Chemistry
1991
Q8215.The molar ratio of carbon to hydrogen of a volatile liquid compound is 1:2. 0.12 g of the liquid on evaporation at s.t.p gave 32 cm³ of vapour. The molecular formula of the liquid is
ACH₂
BC₂H₄
CC₃H₆
DC₆H₁₂
Correct Answer: D
Moles of vapour = 32/22400 = 0.00143 mol. Molar mass = 0.12/0.00143 = 84 g/mol. Empirical formula = CH₂ (M=14). n = 84/14 = 6. Molecular formula = (CH₂)₆ = C₆H₁₂.
JAMB (UTME)
Chemistry
1991
Q8216.It can be deduced from the vapour pressure curves above that
Aliquid I has the highest boiling point
Bliquid II has the highest boiling point
Cliquid III has the highest boiling point
Dliquid III has the lowest boiling point
Correct Answer: A
The liquid with the lowest vapour pressure at a given temperature has the highest boiling point. From the graph, liquid I has the lowest vapour pressure, hence the highest boiling point.
JAMB (UTME)
Chemistry
1991
Q8217.20.00 cm³ of a solution containing 0.53 g of anhydrous Na₂CO₃ in 100 cm³ requires 25.00 cm³ of H₂SO₄ for complete neutralization. The concentration of the acid solution in moles per dm³ is
A0.02
B0.04
C0.06
D0.08
Correct Answer: B
Na₂CO₃ + H₂SO₄ → Na₂SO₄ + H₂O + CO₂. Moles of Na₂CO₃ in 20 cm³ = (0.53/106) × (20/100) = 0.001 mol. Moles of H₂SO₄ = 0.001 mol. Concentration = 0.001 / (25/1000) = 0.04 M.
JAMB (UTME)
Chemistry
1991
Q8218.The minimum volume of oxygen required for the complete combustion of a mixture of 10 cm³ of CO and 15 cm³ of H₂ is
Q8219.What is the partial pressure of hydrogen gas collected over water at standard atmospheric pressure and 25°C if the saturation vapour pressure of water is 23 mm Hg at that temperature?
A737 mm Hg
B763 mm Hg
C777 mm Hg
D737 mm Hg
Correct Answer: A
Partial pressure of dry gas = Total pressure - Vapour pressure of water = 760 - 23 = 737 mm Hg.
JAMB (UTME)
Chemistry
1991
Q8220.The atomic radius Li, Na and K are 1.33 Å, 1.54 Å and 1.96 Å respectively. Which of the following explains this gradation in atomic radius?
AElectropositivity decreases from Li to Na to K
BElectronegativity decreases from Li to Na to K
CThe number of electron shells increase from Li to Na to K
DThe elements are in the same period
Correct Answer: C
As you go down Group 1 (Li → Na → K), the number of electron shells increases, which increases the atomic radius.
JAMB (UTME)
Chemistry
1991
Q8221.Which of the curves in the above graph illustrates the behaviour of an ideal gas?
AW
BX
CY
DZ
Correct Answer: C
For an ideal gas, PV is constant at constant temperature. The graph of PV against P should be a horizontal straight line (curve Y).
JAMB (UTME)
Chemistry
1991
Q8222.Elements X and Y have electronic configurations 1s² 2s² 2p⁴ and 1s² 2s² 2p⁶ 3s² 3p¹ respectively. When they combine, the formula of the compound formed is
AXY
BYX
CX₂Y₃
DY₂X₃
Correct Answer: D
X (atomic number 8) is oxygen, which forms O²⁻. Y (atomic number 13) is aluminium, which forms Al³⁺. The compound formed is Al₂O₃ (Y₂X₃).
JAMB (UTME)
Chemistry
1991
Q8223.The atomic number of cesium is 55 and its atomic mass is 133. The nucleus of a cesium atom therefore contains
A78 protons and 55 electrons
B55 protons and 78 neutrons
C55 neutrons and 78 electrons
D78 neutrons and 55 neutrons
Correct Answer: B
Protons = atomic number = 55. Neutrons = mass number - atomic number = 133 - 55 = 78.
JAMB (UTME)
Chemistry
1991
Q8224.Four elements P, Q, R and S have atomic numbers of 4, 10, 12, and 14 respectively. Which of these elements is a noble gas?
AP
BQ
CR
DS
Correct Answer: B
Atomic number 10 is neon (Ne), which is a noble gas.
JAMB (UTME)
Chemistry
1991
Q8225.How many valence electrons are contained in the element represented by ³¹₁₅P?
A3
B5
C15
D31
Correct Answer: B
Phosphorus (atomic number 15) has electronic configuration 1s² 2s² 2p⁶ 3s² 3p³. It has 5 valence electrons (2 in 3s + 3 in 3p).
JAMB (UTME)
Chemistry
1991
Q8226.In the above set up, substances X and Y are respectively
ALime water and copper (II) tetraoxosulphate (VI)
BPotassium trioxocarbonate (IV) and alkaline pyrogallol
CPotassium hydroxide and alkaline pyrogallol
DPotassium trioxocarbonate (IV) and concentrated tetraoxosulphate (VI) acid
Correct Answer: C
The setup is for the removal of CO₂ and O₂ from air. X is KOH (absorbs CO₂), and Y is alkaline pyrogallol (absorbs O₂).
JAMB (UTME)
Chemistry
1991
Q8227.The gaseous pollutant sulphur (IV) oxide is most likely to be detected in fairly reasonable quantities in the area around a plant for the
Q8228.Calcium hydroxide is added in the treatment of town water supply to
Akill bacteria in the water
Bfacilitate coagulation of organic particles
Cfacilitate sedimentation
Dimprove the taste of the water
Correct Answer: B
Calcium hydroxide (slaked lime) is added to adjust pH and facilitate the coagulation of organic particles and impurities.
JAMB (UTME)
Chemistry
1991
Q8229.A hydrated salt of formula MSO₄·xH₂O contains 45.3% by mass of the water of crystallization. Calculate the value of x.
A3
B5
C7
D10
Correct Answer: C
Molar mass of MSO₄ = 56 + 32 + 64 = 152. Mass of water = 18x. Total mass = 152 + 18x. (18x) / (152 + 18x) = 0.453. 18x = 68.856 + 8.154x. 9.846x = 68.856. x ≈ 7.
JAMB (UTME)
Chemistry
1991
Q8230.If the graph above is a saturated solution of KCl, the mass of crystals deposited when 1 dm³ of the solution is cooled from 80°C to 60°C is
A117.00 g
B58.50 g
C11.70 g
D5.85 g
Correct Answer: B
From the graph, solubility at 80°C = 5.0 mol dm⁻³, at 60°C = 4.0 mol dm⁻³. Change = 1.0 mol dm⁻³. Molar mass of KCl = 39 + 35.5 = 74.5 g/mol. Mass deposited = 1.0 × 74.5 = 74.5 g. (The provided answer B is a typo).
JAMB (UTME)
Chemistry
1991
Q8231.Using 50 cm³ of 1 M potassium hydroxide and 100 cm³ of 1 M tetraoxosulphate (VI) acid, calculate the respective volumes in cm³ of base and acid that would be required to produce the maximum amount of potassium tetraoxosulphate (VI).
Q8232.A solution of calcium bromide contains 20 g dm⁻³. What is the molarity of the solution with respect to calcium bromide and bromide ions?
A0.1, 0.1
B0.1, 0.2
C0.1, 0.05
D0.05, 0.1
Correct Answer: B
Molar mass of CaBr₂ = 40 + 2(80) = 200 g/mol. Molarity = 20/200 = 0.1 M. Each formula unit gives 1 Ca²⁺ and 2 Br⁻. So [Br⁻] = 2 × 0.1 = 0.2 M.
JAMB (UTME)
Chemistry
1991
Q8233.The substance ZnO dissolves in sodium hydroxide solution and mineral acid solution to give soluble products in each case. ZnO is therefore referred to as
Aan allotropic acid
Ban amphoteric oxide
Ca peroxide
Da dioxide
Correct Answer: B
An oxide that reacts with both acids and bases to form salts is called an amphoteric oxide. ZnO is amphoteric.
JAMB (UTME)
Chemistry
1991
Q8234.An acid and its conjugate base
Acan neutralize each other to form a salt
Bdiffer only by a proton
Cdiffer only by the opposite charges they carry
Dare always neutral substances
Correct Answer: B
According to the Brønsted-Lowry theory, an acid and its conjugate base differ by a single proton (H⁺).
JAMB (UTME)
Chemistry
1991
Q8235.The same current is passed for the same time through solutions of AgNO₃ and CuSO₄ connected in series. How much silver will be deposited if 1.0 g of copper is produced?
A1.7 g
B3.4 g
C6.8 g
D13.6 g
Correct Answer: B
Equivalent mass of Cu = 63.5/2 = 31.75. Equivalent mass of Ag = 108/1 = 108. Mass of Ag = (1.0/31.75) × 108 = 3.4 g.
JAMB (UTME)
Chemistry
1991
Q8236.What is discharged at the cathode during the electrolysis of copper (II) tetraoxosulphate (VI) solution?
ACu²⁺ only
BH⁺ only
CCu²⁺ and H⁺
DCu²⁺ and SO₄²⁻
Correct Answer: A
In the electrolysis of CuSO₄ solution using inert electrodes, Cu²⁺ ions are preferentially discharged at the cathode because they are less electropositive than hydrogen.
JAMB (UTME)
Chemistry
1991
Q8237.An element, Z forms an anion whose formula is [Z(CN)₆]ⁿ⁻. If Z has an oxidation number of +2, what is the value of y?
A-2
B3
C-4
D-5
Correct Answer: C
Let the charge on CN be -1. The complex ion is [Z(CN)₆]ⁿ⁻. Z is +2, and 6 CN⁻ contribute -6. Total charge = +2 + (-6) = -4. So n = -4.
JAMB (UTME)
Chemistry
1991
Q8238.Which of the reactions is NOT an example of a redox reaction?
AI, II, III
BII and III
CIII and IV
DIV only
Correct Answer: D
Reaction IV is a decomposition reaction with no change in oxidation states. It is not a redox reaction.
JAMB (UTME)
Chemistry
1991
Q8239.The above diagram gives the potential energy profile of the catalysed and uncatalysed reactions of X(g) + Y(g) → XY(g). Deduce the respective activation energies in kJ of the catalysed and uncatalysed reverse reactions.
A300, 500
B500, 300
C-300, -500
D-500, -300
Correct Answer: A
From the diagram, the activation energy for the catalysed forward reaction is 300 kJ. For the uncatalysed forward reaction, it is 500 kJ. The reverse reaction activation energies are the same as forward since the reaction is the same.
JAMB (UTME)
Chemistry
1991
Q8240.The combustion of ethene, C₂H₄, is given by the equation C₂H₄ + 3O₂ → 2CO₂ + 2H₂O; ΔH = -1428 kJ. If the molar heats of formation of water and carbon (IV) oxide are -286 kJ and -396 kJ respectively. Calculate the molar heat of formation of ethane in kJ.
Q8241.CO(g) + H₂O(g) ⇌ CO₂(g) + H₂(g); ΔH = -41000 J. Which of the following factors favour the formation of hydrogen in the above reaction?
AI, III, and IV
BIII only
CII, III and I
DIV only
Correct Answer: A
The reaction is exothermic (ΔH negative), so low temperature favours the forward reaction. It is a gas-phase reaction with no change in the number of moles (2 moles on both sides), so pressure has no effect. Use of excess steam (increasing reactant concentration) favours the forward reaction.
JAMB (UTME)
Chemistry
1991
Q8242.The above graph shows a typical heating curve from the solid phase through the liquid phase to the gaseous phase of a substance. What part of the curve shows solid and liquid in equilibrium?
AT
BU
CX
DY
Correct Answer: C
The horizontal portion of the heating curve where temperature remains constant represents the phase change (melting). This is where solid and liquid are in equilibrium.
JAMB (UTME)
Chemistry
1991
Q8243.Which of the following represents the balanced equation for the reaction of copper with concentrated trioxonitrate (V) acid?
A2NHO₃ → Cu(NO₃)₂ + H₂(g)
BCu + 4HNO₃ → Cu(NO₃)₂ + 2H₂O + 2NO₂(g)
C3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 4H₂O + 2NO(g)
D3Cu + 4HNO₃ → 3Cu(NO₃)₂ + 2H₂O + 2NO₂(g)
Correct Answer: B
Copper reacts with concentrated HNO₃ to produce NO₂ gas: Cu + 4HNO₃ → Cu(NO₃)₂ + 2H₂O + 2NO₂.
JAMB (UTME)
Chemistry
1991
Q8244.The catalyst used in the contact process for the manufacture of tetraoxosulphate (VI) acid is
AManganese (IV) oxide
BManganese (II) tetraoxosulphate (IV)
CVanadium (V) oxide
DIron metal
Correct Answer: C
The contact process uses vanadium(V) oxide (V₂O₅) as a catalyst to oxidize SO₂ to SO₃.
JAMB (UTME)
Chemistry
1991
Q8245.Some products of destructive distillation of coal are
Acarbon (IV) oxide and ethanoic acid
Btrioxocarbonate (IV) acid and methanoic acid
Cproducer gas and water gas
Dcoke and ammoniacal liquor
Correct Answer: D
Destructive distillation of coal produces coke, coal tar, ammoniacal liquor, and coal gas.
JAMB (UTME)
Chemistry
1991
Q8246.Gunpowder is made from charcoal, sulphur and potassium trioxonitrate (V). The salt in the mixture performs the function of
Aan oxidant
Ba reductant
Ca solvent
Da catalyst
Correct Answer: A
Potassium trioxonitrate(V) (KNO₃) is an oxidizing agent. It provides oxygen for the rapid combustion of charcoal and sulphur.
JAMB (UTME)
Chemistry
1991
Q8247.Which of the following reaction(s) is (are) feasible?
AI only
BII and IV
CI and III
DIII and IV
Correct Answer: B
A more reactive halogen can displace a less reactive halogen from its salt solution. Br₂ can displace I⁻ (II). Br₂ can also oxidize Fe²⁺ to Fe³⁺ (IV). Cl₂ cannot displace F⁻ (III), and Br₂ cannot displace Cl⁻ (I).
JAMB (UTME)
Chemistry
1991
Q8248.Bleaching powder, CaOCl₂·H₂O, deteriorates on exposure to air because
Ait loses its water of crystallization
Batmospheric nitrogen displaces chlorine from it
Ccarbon (IV) oxide of the atmosphere displaces chlorine from it
Dbleaching agents should be stored in solution
Correct Answer: C
Bleaching powder reacts with CO₂ in the air to release chlorine gas, which reduces its bleaching power.
JAMB (UTME)
Chemistry
1991
Q8249.The product of the thermal decomposition of ammonium trioxonitrate (V) are
ANO₂ and oxygen
BNH₃ and oxygen
Cnitrogen and water
DN₂O and water
Correct Answer: D
Ammonium trioxonitrate(V) (NH₄NO₃) decomposes on heating to give nitrous oxide (N₂O) and water.
JAMB (UTME)
Chemistry
1991
Q8250.The scale of a chemical balance is made of iron plate and coated with copper electrolytically because
Airon is less susceptible to corrosion than copper
Bcopper is less susceptible to corrosion than iron
Ccopper is less susceptible to corrosion than ion
Dcopper and ion are equally susceptible to corrosion
Correct Answer: B
Copper is less reactive than iron and forms a protective oxide layer, making it more resistant to corrosion.