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Instruction
JAMB Chemistry 2015
JAMB (UTME)
Chemistry
2015
Q6701.12.0g of a mixture of potassium carbonate and potassium chloride were dissolved in a 250cm³ standard flask. 25cm³ of this solution required 40.00cm³ of 0.1M HCl for neutralization. What is the percentage by weight of K₂CO₃ in the mixture (K = 39, O = 16, C = 12)
A60
B72
C82
D92
Correct Answer: D
The reaction is K₂CO₃ + 2HCl → 2KCl + H₂O + CO₂. Moles of HCl = 0.1 × 40/1000 = 0.004 mol. Moles of K₂CO₃ in 25cm³ = 0.004/2 = 0.002 mol. Moles in 250cm³ = 0.02 mol. Mass of K₂CO₃ = 0.02 × 138 = 2.76 g. Percentage = (2.76/12) × 100 = 23%. (The provided answer D is a typo; the correct percentage is 23%).
JAMB (UTME)
Chemistry
2015
Q6702.Electron affinity
A1 and 2
B1, 2 and 3
C3 and 4
D1, 2, 3 and 4
Correct Answer: C
Across a period (left to right), ionization energy increases, electronegativity increases, and electron affinity increases. Atomic radius decreases. Therefore, properties that increase are 1, 3, and 4.
JAMB (UTME)
Chemistry
2015
Q6703.An element Z, contained 90% of ⁸Z¹⁶ and 10% of ⁸Z¹⁸. its relative atomic mass is
Q6704.What are the possible oxidation numbers for an element if its atomic number is 17?
A-1 and 7
B-1 and 6
C-3 and 5
D-2 and 6
Correct Answer: A
Atomic number 17 is chlorine. Chlorine can have oxidation states of -1 (in chlorides) and +7 (in perchlorates), among others.
JAMB (UTME)
Chemistry
2015
Q6705.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
2015
Q6706.10.0 dm³ of air containing H₂S as an impurity was passed through a solution of Pb(NO₃)₂ until all the H₂S had reacted. The precipitate of PbS was found to weigh 5.02 g. According to the equation: Pb(NO₃)₂ + H₂S → PbS + 2HNO₃ the percentage by volume of hydrogen sulphide in the air is
A50.2
B47.0
C4.70
D0.47
Correct Answer: C
Molar mass of PbS = 207 + 32 = 239 g/mol. Moles of PbS = 5.02/239 = 0.021 mol. Moles of H₂S = 0.021 mol. Volume of H₂S at s.t.p. = 0.021 × 22.4 = 0.47 dm³. Percentage by volume = (0.47/10) × 100 = 4.7%.
JAMB (UTME)
Chemistry
2015
Q6707.A quantity of air was passed through a weighed amount of alkaline pyrogallol. An increase in the weight of the pyrogallol would result from the absorption of
Anitrogen
Bneon
Coxygen
Dcarbon (IV) oxide
Correct Answer: C
Alkaline pyrogallol absorbs oxygen from air. An increase in weight indicates absorption of oxygen.
JAMB (UTME)
Chemistry
2015
Q6708.Water for town supply is chlorinated to make it free from
Abad odour
Bbacteria
Ctemporary hardness
Dpermanent hardness
Correct Answer: B
Chlorination kills bacteria and other microorganisms in water, making it safe for drinking.
JAMB (UTME)
Chemistry
2015
Q6709.4.0 g of sodium hydroxide in 250cm³ of solution contains
Q6710.A major effect of oil pollution in coastal waters is the
Adestruction of marine life
Bdesalination of the water
Cincrease in the acidity of the water
Ddetoxification of the water
Correct Answer: A
Oil pollution in coastal waters destroys marine life by coating the feathers of birds and the gills of fish, preventing them from breathing and insulating them.
JAMB (UTME)
Chemistry
2015
Q6711.In general, an increase in temperature increases the solubility of a solute in water because
Amore solute molecules collide with each other
Bmost solutes dissolve with the evolution of heat
Cmore solute molecules dissociate at higher temperatures
Dmost solutes dissolve with absorption of heat.
Correct Answer: D
For most solutes, the dissolution process is endothermic (absorbs heat). According to Le Chatelier's principle, increasing the temperature favours the endothermic process, increasing solubility.
JAMB (UTME)
Chemistry
2015
Q6712.The relatively high boiling points of alkanols are due to
Aionic bonding
Baromatic character
Ccovalent bonding
Dhydrogen bonding.
Correct Answer: D
Alkanols (alcohols) have high boiling points compared to alkanes of similar molecular mass because they can form hydrogen bonds with each other.
JAMB (UTME)
Chemistry
2015
Q6713.Given that 15.00cm³ of H₂SO₄ was required to completely neutralize 25.00cm³ of 0.125 mol dm⁻³ NaOH, calculate the molar concentration of the acid solution
A0.925 mol dm⁻³
B0.104 mol dm⁻³
C0.115 mol dm⁻³
D0.125 mol dm⁻³
Correct Answer: B
The reaction is H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O. Moles of NaOH = 0.125 × 25/1000 = 0.003125 mol. Moles of H₂SO₄ = 0.003125/2 = 0.0015625 mol. Concentration of H₂SO₄ = 0.0015625/0.015 = 0.104 mol dm⁻³.
JAMB (UTME)
Chemistry
2015
Q6714.What volume of 0.1 mol dm⁻³ solution of tetraoxosulphate (VI) acid would be needed to dissolve 2.86g of sodium trioxocarbonate (IV) decahydrate crystals? [H = 1, C = 12, O = 16, S = 32, Na = 23]
pH depends on the concentration of H⁺ ions, not volume. M/10 = 0.1 M, M/5 = 0.2 M, M/8 = 0.125 M. The highest concentration is M/5 (0.2 M), which has the lowest pH. (The provided answer D is a typo; the correct answer is C).
JAMB (UTME)
Chemistry
2015
Q6716.In which order are the following salts sensitive to light?
AAgI > AgCl > AgBr
BAgCl > AgI > AgBr
CAgBr > AgCl > AgI
DAgCl > AgBr > AgI
Correct Answer: D
Silver halides are sensitive to light. The order of sensitivity is AgCl > AgBr > AgI. AgCl is the most light-sensitive.
JAMB (UTME)
Chemistry
2015
Q6717.A metal M displaces Zinc from Zinc chloride solution. This shows that
AM is more electronegative than Zinc
BZinc is above hydrogen in the series.
CM is more electropositive than zinc.
Delectrons flow from zinc to M.
Correct Answer: C
A metal can displace another from its salt solution if it is more electropositive (more reactive) than the other. So M is more electropositive than zinc.
JAMB (UTME)
Chemistry
2015
Q6718.Steam changes the colour of anhydrous cobalt (II) chloride from
Ablue to pink
Bwhite to red
Cwhite to green
Dblue to white
Correct Answer: A
Anhydrous cobalt(II) chloride is blue. When it absorbs water (steam), it forms hydrated cobalt(II) chloride, which is pink.
JAMB (UTME)
Chemistry
2015
Q6719.When at equilibrium, which of the reactions below will shift to the right if the pressure is increased and the temperature is kept constant?
A2SO₃(g) ⇌ 2SO₂(g) + O₂(g)
B2CO₂(g) ⇌ 2CO(g) + O₂(g)
C2H₂(g) + O₂(g) ⇌ 2H₂O(g)
D2NO(g) ⇌ N₂(g) + O₂(g)
Correct Answer: C
Increasing pressure shifts the equilibrium to the side with fewer gas molecules. Reaction C has 3 moles of gas on the left (2H₂ + O₂) and 2 moles on the right (2H₂O), so it will shift right.
JAMB (UTME)
Chemistry
2015
Q6720.2CO(g) + O₂(g) → 2CO₂(g)
A-503.7 kJ
B-282.6 kJ
C+282.6 kJ
D+503.7 kJ
Correct Answer: B
ΔH = ΣΔHf(products) - ΣΔHf(reactants) = [2(-393.0)] - [2(-110.4) + 0] = -786.0 - (-220.8) = -786.0 + 220.8 = -565.2 kJ. (The provided answer B is a typo).
JAMB (UTME)
Chemistry
2015
Q6721.Which of these properties gives a solid its definite shape?
AStrong intermolecular attraction
BHigh melting point
CHigh boiling point
DWeak intermolecular attraction
Correct Answer: A
Strong intermolecular attraction holds the particles of a solid closely together in fixed positions, giving it a definite shape.
JAMB (UTME)
Chemistry
2015
Q6722.When a crystal was added to the clear solution of its salt, the crystal did not dissolve and the solution remained unchanged. This showed that the solution was
Asupersaturated
Bconcentrated
Cunsaturated
Dsaturated
Correct Answer: D
A saturated solution is one in which no more solute can dissolve at a given temperature. Adding a crystal to a saturated solution results in no further dissolution.
JAMB (UTME)
Chemistry
2015
Q6723.If the electron configuration of an element is 1s² 2s² 2p⁵, how many unpaired electrons are there?
A2
B5
C1
D4
Correct Answer: C
The 2p sublevel has 5 electrons. According to Hund's rule, the first three electrons occupy separate orbitals with parallel spins. The remaining two electrons pair up in two of the orbitals. Therefore, there is 1 unpaired electron.
JAMB (UTME)
Chemistry
2015
Q6724.The substance that is used in the steel industry for the removal of carbon, sulphur and phosphorus impurities from pig iron is
Aoxygen
Bchlorine
Cnitrogen
Dhydrogen
Correct Answer: A
Oxygen is blown through molten pig iron in a converter to oxidize carbon, sulphur, and phosphorus impurities, removing them as gases or slag.
JAMB (UTME)
Chemistry
2015
Q6725.Hydrogen sulphide gas can act as
Aan oxidizing agent
Ba dehydrating agent
Ca bleaching agent
Da precipitating agent.
Correct Answer: D
Hydrogen sulphide (H₂S) acts as a precipitating agent in qualitative analysis. It precipitates metal ions as insoluble sulphides.
JAMB (UTME)
Chemistry
2015
Q6726.Which of the following is used as a rocket fuel?
AHNO₃
BCH₃COOH
CH₂SO₄
DHCl
Correct Answer: A
Concentrated nitric acid (HNO₃) is used as an oxidizer in rocket fuels.
JAMB (UTME)
Chemistry
2015
Q6727.The bleaching action of chlorine is effective due to the presence of
AHydrogen chloride
BWater
CAir
DOxygen
Correct Answer: B
Chlorine bleaches by oxidation in the presence of water. It reacts with water to form hypochlorous acid (HOCl), which is the active bleaching agent.
JAMB (UTME)
Chemistry
2015
Q6728.Mineral acids are usually added to commercial hydrogen peroxide to
AOxidize it
Bdecompose it
Cminimize its decomposition
Dreduce it to water and oxygen.
Correct Answer: C
Mineral acids are added to hydrogen peroxide to stabilize it and minimize its decomposition into water and oxygen.
JAMB (UTME)
Chemistry
2015
Q6729.Aluminium containers are frequently used to transport trioxonitrate (v) acid because aluminium
Ahas a low density
Bdoes not react with the acid
Cdoes not corrode
Dhas a silvery-white appearance
Correct Answer: B
Aluminium does not react with concentrated trioxonitrate(V) acid (HNO₃) due to the formation of a protective oxide layer (passivation). Therefore, it can be used to transport the acid.
JAMB (UTME)
Chemistry
2015
Q6730.Ethyne is passed through a hot tube containing organo-nickel catalyst to produce
AIsoprene
Bpolythene
Cethanol
Dbenzene
Correct Answer: D
Ethyne (acetylene) undergoes cyclization when passed through a hot tube containing an organo-nickel catalyst to produce benzene.
JAMB (UTME)
Chemistry
2015
Q6731.The process of converting starch to ethanol is
Acracking
Bdistillation
Cfermentation
Doxidation
Correct Answer: C
Fermentation is the process by which starch is converted to ethanol using yeast (zymase enzyme).
JAMB (UTME)
Chemistry
2015
Q6732.An endothermic reaction is one during which heat is __ and can be represented by the symbol __. Which of the following combinations can be used accurately to complete the above definition?
Aliberated -ΔH
Bliberated +ΔH
Cabsorbed -ΔH
Dabsorbed +ΔH
Correct Answer: D
An endothermic reaction absorbs heat, and the enthalpy change (ΔH) is positive (+ΔH).
JAMB (UTME)
Chemistry
2015
Q6733.Consider the following exothermic reaction 2SO₂(g) + O₂(g) ⇌ 2SO₃(g). If the temperature of the reaction is reduced from 800°C to 500°C, and no other change takes place, then
Athe reaction rate increases
Bconcentration of SO₂ decreases
Cconcentration of SO₂ increases
DSO₂ gas becomes unreactive
Correct Answer: C
The reaction is exothermic (forward reaction releases heat). According to Le Chatelier's principle, decreasing the temperature favours the exothermic (forward) reaction, so the equilibrium shifts to the right, decreasing the concentration of SO₂ and increasing that of SO₃. (Note: The provided answer C is a typo; the correct answer is B).
Instruction
JAMB Chemistry 2016
JAMB (UTME)
Chemistry
2016
Q6734.An element X has two isotopes ²⁰₁₀X and ²²₁₀X present in the ratio 1:3. The relative atomic mass of X would be
Q6735.200cm³ of oxygen diffuse through a porous plug in 50 seconds. How long will 80cm³ of methane (CH₄) take to diffuse through the same porous plug under the same conditions?
Q6736.Which of the following terms indicates the number of bonds that can be formed by an atom?
Aoxidation number
BValence
CAtomic number
DElectronegativity
Correct Answer: B
Valence (valency) is the combining power of an element — the number of bonds it can form.
JAMB (UTME)
Chemistry
2016
Q6737.The diagram above represents an atom of
Amagnesium
Bhelium
Cchlorine
Dneon
Correct Answer: A
The diagram shows 12 electrons in 3 shells (2, 8, 2), which is the electronic configuration of magnesium (atomic number 12).
JAMB (UTME)
Chemistry
2016
Q6738.Which of the following gases is the most dangerous pollutant?
AHydrogen sulphide
BCarbon Monoxide
CSulphur(IV) oxide
DCarbon Dioxide
Correct Answer: B
Carbon monoxide (CO) is the most dangerous pollutant because it is colourless, odourless, and binds strongly to haemoglobin, preventing oxygen transport. It can cause death at relatively low concentrations.
JAMB (UTME)
Chemistry
2016
Q6739.A side effect of soft water is that
AIt gives offensive taste
Bexcess calcium is precipitated
Cit attacks lead contained in pipes
Dit encourages the growth of bacteria
Correct Answer: C
Soft water is acidic and can dissolve lead from pipes, leading to lead poisoning. Hard water does not attack lead pipes as much because the carbonate scale protects them.
JAMB (UTME)
Chemistry
2016
Q6740.Farmlands affected by crude oil spillage can be decontaminated by
Aadding acidic solutions
Busing aerobic bacteria
Cpouring water on the affected area
Dburning off the oil from the area
Correct Answer: B
Using aerobic bacteria (bioremediation) is an effective method for decontaminating farmlands affected by crude oil spillage. Bacteria break down the hydrocarbons into harmless substances.
JAMB (UTME)
Chemistry
2016
Q6741.Which of the following functional groups will give gas bubbles when treated with a saturated solution of sodium hydrogen trioxocarbonate(IV)?
A-NH₃
B-COOH
C-OH
D-CHO
Correct Answer: B
The carboxylic acid group (-COOH) reacts with sodium hydrogen trioxocarbonate(IV) (NaHCO₃) to produce carbon(IV) oxide gas (bubbles).
JAMB (UTME)
Chemistry
2016
Q6742.The oxidation state of Cr in K₂Cr₂O₇ is
A+7
B+6
C+5
D+4
Correct Answer: B
K is +1, O is -2. Let Cr be x. 2(+1) + 2x + 7(-2) = 0 → 2 + 2x - 14 = 0 → 2x = 12 → x = +6.
JAMB (UTME)
Chemistry
2016
Q6743.2Na₂O₂(s) + 2H₂O(l) → 4NaOH(s) + O₂(g)
ANa₂O₂
BNaOH
CH₂O
DO₂
Correct Answer: A
In Na₂O₂, oxygen has an oxidation state of -1. In O₂, it is 0 (oxidized), and in NaOH, it is -2 (reduced). Na₂O₂ undergoes both oxidation and reduction (disproportionation). The substance oxidized is Na₂O₂.
JAMB (UTME)
Chemistry
2016
Q6744.Z in diagram above represents
Aheat of reaction
Bactivation energy
Cfree energy
Dentropy of reaction
Correct Answer: A
In the energy profile diagram, Z represents the heat of reaction (enthalpy change, ΔH), which is the difference in energy between reactants and products.
JAMB (UTME)
Chemistry
2016
Q6745.The nucleus of an atom contains
Aprotons only
Bneutrons only
Cprotons and electrons
Dprotons and neutrons
Correct Answer: D
The nucleus of an atom contains protons and neutrons (collectively called nucleons). Electrons orbit the nucleus.
JAMB (UTME)
Chemistry
2016
Q6746.Which of the following does NOT happen when a Zinc rod is introduced into a solution of Copper (II) sulphate?
AElectrons flow towards the zinc rod
BThe Zinc rod dissolves
CThe temperature of the solution changes
DThe blue colour of the solution gradually disappears
Correct Answer: A
Zinc is more reactive than copper, so it displaces copper from CuSO₄. Electrons flow from zinc (anode) to copper (cathode), not towards the zinc rod. The blue colour fades as Cu²⁺ is reduced to Cu.
JAMB (UTME)
Chemistry
2016
Q6747.Which of the following statements is correct during the electrolysis of a caustic soda solution using platinum electrodes?
AOxygen gas is given off at the cathode
BHydrogen gas is given off at the anode
CSodium metal is deposited at the cathode
DAlkalinity at the cathode increases
Correct Answer: D
During the electrolysis of caustic soda (NaOH) solution with platinum electrodes, H₂ is produced at the cathode and O₂ at the anode. The cathode region becomes more alkaline as OH⁻ concentration increases. Sodium metal is not deposited because water is preferentially reduced.
JAMB (UTME)
Chemistry
2016
Q6748.Which of the following statements is INCORRECT?
AFractional distillation of crude petroleum will give the following hydrocarbon fuels in order of increasing boiling point: Butane < Petrol < Kerosene
BH₂C=CH₂ will serve as a monomer in the preparation of polythene
CBoth but-1-ene and but-1-yne will decolourize bromine readily
DCalcium carbide will react with water to form any alkyne
Correct Answer: D
Calcium carbide (CaC₂) reacts with water to form ethyne (acetylene), not "any alkyne." Only ethyne is produced.
JAMB (UTME)
Chemistry
2016
Q6749.The iron (III) oxide impurity in bauxite can be removed by
Afractional crystallization in acid solution
Bdissolution in sodium hydroxide and filtration
Cextraction with concentrated ammonia and reprecipitation
Delectrolysis of molten mixture
Correct Answer: B
Bauxite (Al₂O₃) is purified by dissolving in NaOH. Al₂O₃ is amphoteric and dissolves, while Fe₂O₃ (iron(III) oxide) is basic and does not dissolve. It is filtered off.
JAMB (UTME)
Chemistry
2016
Q6750.Aluminium is extracted commercially from its ore by
Aheating aluminium oxide with coke in a furnace
Bthe electrolysis of fused aluminium oxide in cryolite
Ctreating cryolite with sodium hydroxide solution under pressure
Dheating sodium aluminium silicate to a high temperature
Correct Answer: B
Aluminium is extracted by the electrolysis of fused alumina (Al₂O₃) dissolved in molten cryolite (Na₃AlF₆) at about 950°C.