All 41 questions from the Joint Admissions and Matriculation Board (JAMB) Mathematics 2022 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
Advertisement
The IUPAC name of CH₂BrCHClCH₂CH₂Br is
Parent chain = pentane. Substituents: Br at C1, Cl at C2, Br at C5. Counting from the end closer to substituents: 1,5-dibromo-2-chloropentane.
If 25 cm³ of hydrogen is sparked with 5 cm³ of oxygen, the volume of the unreacted oxygen is
2H₂ + O₂ → 2H₂O. 25 cm³ H₂ requires 12.5 cm³ O₂. Only 5 cm³ O₂ is available, so O₂ is the limiting reagent. All O₂ is consumed. Unreacted O₂ = 0 cm³.
The element common to Alnico, steel and Permalloy is
Alnico = Al + Ni + Co + Fe. Permalloy = Fe + Ni. Steel = Fe + C. Iron (Fe) is the element common to all three alloys.
What bond is present in hydrated copper(ii) ions?
In [Cu(H₂O)₆]²⁺, water molecules donate lone pairs to Cu²⁺ to form coordinate (dative) bonds. The bond is dative (coordinate) covalent.
Which of the following pairs are oxidising agents?
Halogens (Group VII) are good oxidising agents. Chlorine and bromine both readily accept electrons (are reduced). H₂S and sodium are reducing agents.
How many atoms are present in 12 g of magnesium?
Moles of Mg = 12/24 = 0.5 mol. Atoms = 0.5 × 6.02 × 10²³ = 3.01 × 10²³.
A hydrogen atom which has lost an electron contains
Protium (¹H): 1 proton, 0 neutrons, 1 electron. Losing 1 electron leaves only 1 proton (H⁺ ion).
Chlorination of water for town supply is carried out to
Chlorine is added to water to kill bacteria and other micro-organisms (disinfection/sterilisation). It kills germs by oxidation.
The number of hydroxonium ions produced by one molecule of an acid in aqueous solution is its
Basicity (acidity) of an acid is the number of H⁺ (hydroxonium) ions it can produce per molecule. HCl = 1, H₂SO₄ = 2, H₃PO₄ = 3.
An increase in entropy can best be illustrated by
Entropy increases with disorder. Mixing gases increases disorder (more possible arrangements). Solidification, freezing, and condensation all decrease entropy (more ordered states).
A piece of filter paper moistened with lead(ii) ethanoate turns black when the paper is dropped into a gas likely to be
H₂S + Pb(CH₃COO)₂ → PbS (black precipitate) + 2CH₃COOH. Lead ethanoate paper turning black is the test for hydrogen sulphide.
Commercial bleaching can be carried out using
Chlorine (Cl₂) bleaches by oxidation; sulphur(iv) oxide (SO₂) bleaches by reduction. Both are used as bleaching agents commercially.
A major factor considered in selecting a suitable method for preparing a simple salt is its
Solubility determines the preparation method: soluble salts by neutralisation/direct combination; insoluble salts by precipitation (double decomposition).
Mineral acids are usually added to commercial hydrogen peroxide to
Mineral acids (especially H₃PO₄) are added to hydrogen peroxide to stabilise it and minimise decomposition (2H₂O₂ → 2H₂O + O₂).
Geometric isomerism can exist in
Hex-3-ene (CH₃CH₂CH=CHCH₂CH₃) has two different groups on each carbon of the double bond, allowing cis and trans isomers. Propene and 3-methylbut-1-ene have a –CH₂– end, limiting geometric isomerism.
Ethanol reacts with concentrated tetraoxosulphate(vi) acid at a temperature above 170°C to form
At ~170°C with conc. H₂SO₄ (excess acid), ethanol undergoes dehydration to form ethene: CH₃CH₂OH → CH₂=CH₂ + H₂O. (At ~140°C with excess alcohol, ethoxyethane forms.)
On exposure to the atmosphere, a hydrated salt loses its water of crystallisation to become anhydrous. This phenomenon is called
Efflorescence is the loss of water of crystallisation when a hydrated salt is exposed to the atmosphere (e.g. Na₂CO₃·10H₂O → Na₂CO₃·H₂O + 9H₂O).
Cr₂O₇²⁻ + H₂O ⇌ 2CrO₄²⁻ + 2H⁺ — What happens when the concentration of H⁺ is increased?
Adding H⁺ increases product concentration. By Le Chatelier's principle, the equilibrium shifts left to reduce H⁺ concentration.
Ethyne is passed through a hot tube containing organo-nickel catalyst to produce
3C₂H₂ →(organo-Ni, Δ)→ C₆H₆ (benzene). Trimerisation of ethyne gives benzene.
A hydrocarbon has an empirical formula CH and vapour density of 39. Determine its molecular formula.
M.M. = 2 × VD = 78. (CH)ₙ = 78. 13n = 78. n = 6. Molecular formula = C₆H₆ (benzene).
The shape of methane is
CH₄ has 4 bonding pairs and 0 lone pairs on carbon. VSEPR theory gives a tetrahedral shape with H–C–H bond angles of 109.5°.
Y in the energy diagram (Y = enthalpy change of reaction) represents
In a reaction energy profile: X = activation energy (energy barrier), Y = enthalpy change (ΔH, overall energy difference), Z = transition state/activated complex.
An aqueous solution of Na₂CO₃ is
Na₂CO₃ is a salt of a weak acid (H₂CO₃) and strong base (NaOH). It hydrolyses in water to give an alkaline solution: CO₃²⁻ + H₂O ⇌ HCO₃⁻ + OH⁻.
Which of the following correctly expresses Boyle's law?
Boyle's Law: at constant temperature, pressure is inversely proportional to volume: P ∝ 1/V (or PV = constant). Charles' Law: V ∝ T (constant P).
Which of the factors would affect the equilibrium constant?
The equilibrium constant K is only affected by temperature. Changes in concentration, pressure and volume shift the equilibrium position but do not change the value of K.
Which of the following is non-biodegradable?
Plastics cannot be broken down by micro-organisms and persist indefinitely in the environment. Wood, paper and organic matter are biodegradable.
Heavy chemicals are those produced in large quantities while fine chemicals are those produced in very small quantities but with a higher degree of purity. Which of the following is a fine chemical?
Drugs (pharmaceuticals) are fine chemicals — produced in small quantities to high purity. H₂SO₄, NaOH and NH₃ are heavy chemicals produced in large industrial quantities.
Evidently there are two unpaired electrons in the p-orbitals of oxygen. What is the electronic configuration of ₈O?
O (Z=8): 1s²2s²2p⁴. The 2p⁴ electrons fill as: 2px↑↓, 2py↑, 2pz↑ — giving 2 unpaired electrons in the p-orbitals.
Gamma rays have the highest penetration power but the lowest ionising power. Alpha particles have the highest ionising power but the lowest penetration power. Which has the lowest ionisation power?
Ionising power: α > β > γ (X-rays). Gamma rays have the lowest ionising power but the highest penetrating power.
The mass of Mg atoms present in 48 g of Mg is
Moles of Mg = 48/24 = 2 mol. Atoms = 2 × 6.02 × 10²³ = 1.204 × 10²⁴.
S.V.P of H₂O at 10°C = 5 mmHg. 50 cm³ of gas collected over water at 10°C and 765 mmHg. Volume at STP?
Dry gas pressure = 765 − 5 = 760 mmHg. At STP (273K, 760 mmHg): V₂ = V₁T₂/T₁ = (50 × 273)/283 = 48.23 cm³.
Group VII elements are electron acceptors; they are diatomic, highly electronegative and good oxidising agents. Which is correct about Group VII?
Group VII (halogens) are good oxidising agents. They are diatomic, not monoatomic; highly electronegative, not electropositive; and are electron acceptors, not donors.
Ammonia describes which of the following?
Ammonia is the only known gas that turns red litmus blue (it is the only alkaline gas). It also forms white fumes with HCl, but this is a property, not its defining description.
Dehydrogenase is a type of enzyme that catalyses the oxidation-reduction reaction by removing hydrogen atoms from a substrate. What type of enzyme is dehydrogenase?
Dehydrogenase is an oxidoreductase enzyme. It catalyses oxidation-reduction (redox) reactions by transferring hydrogen atoms (or electrons) from a substrate to an acceptor.
The law of multiple proportion states that when two elements combine in more than one ratio, different masses of one element combining with a fixed mass of the other are in simple whole-number ratios. This illustrates the law of
The law of multiple proportion (Dalton): the same elements can combine in different ratios to form different compounds, and those ratios are simple whole numbers.
The oxidation states of chlorine in HOCl, HClO₃ and HClO₄ are respectively
HOCl: H(+1) + O(−2) + Cl = 0 → Cl = +1. HClO₃: Cl = +5. HClO₄: Cl = +7. Oxidation states are +1, +5, +7.
Since NH₄Cl is formed from a strong acid (HCl) and a weak base (NH₄OH), the hydrolysis of NH₄Cl gives an acidic solution. Which of the following is correct?
NH₄Cl is a salt of strong acid (HCl) and weak base (NH₃). It undergoes hydrolysis: NH₄⁺ + H₂O ⇌ NH₃ + H₃O⁺, giving an acidic solution.
Ethene (also known as ethylene) plays an important role in the ripening of fruits. What role does ethene play?
Ethene is a plant hormone (phytohormone) that triggers and accelerates fruit ripening. It is used commercially to ripen bananas and other fruits.
Ionic compounds have high melting and boiling points. Which of the following is correct?
Ionic compounds have strong electrostatic attractions between ions in a crystal lattice. Large amounts of energy are needed to break these attractions, giving high melting and boiling points.
This is known as activation energy — the minimum amount of energy required for effective collisions between reacting particles. What is the activation energy?
Activation energy is the minimum energy that reacting particles must possess for effective collisions to occur and produce a chemical reaction.
Mercury is the only stable liquid elemental metal at room temperature. Which of the following metals is liquid at room temperature?
Mercury (Hg) is the only metal that is liquid at standard room temperature (25°C). All other metals are solid at room temperature.
Advertisement
…and/or go further with premium services and No Ads.