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waec2025chemistry
Q1. Iron produced directly from a blast furnace is
Awrought iron
Bcast iron
Cpig iron
Dcarbon steel
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Q2. A metal that can be found in the free state in nature is
Asilver
BZinc
CIron
Dcopper
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Q3. From the graph, it can be inferred that
Athe solubility of X and Y is the same at all temperatures
Bthe solubility of X, Y and Z is temperature dependent
Csolubility of Z increases as temperature increases
Dsolubility of Y increases steadily as temperature increases
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waec2025chemistry
Q4. The property of metal that makes it suitable as a catalyst is
Afilled f-orbital
Bpartially filled d-orbitals
Cpartially filled f-orbital
Dfilled d-orbital
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waec2025chemistry
Q5. In the laboratory preparation of oxygen using potassium trioxochlorate(V), tetraoxomanganate(VII) is usually not recommended in modern laboratory because
Ait forms explosive mixture with carbonaceous materials
Bit is explosive
Cit reacts with the catalyst
Dit is hazardous
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waec2025chemistry
Q6. Alkanoic acids have higher boiling points than alkanols because
Aalkanoic acids are more volatile than alkanols
Balkanols are more polar than alkanoic acids
Calkanoic acids are larger molecules
Dalkanoic acids form stronger hydrogen bonds
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waec2025chemistry
Q7. The nitrogenous compound in dead materials in the soil is converted to
Aammonia
Btrioxonitrate(V)
Cammonium salts
Ddioxonitrate(III)
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waec2025chemistry
Q8. The molecule with the highest number of lone pair of electrons is
AH₂O
BNH₃
CCH₄
DCO₂
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waec2025chemistry
Q9. In the electrolysis of brine using neutral electrodes, which ion is discharged at the anode?
A2H⁺
BNa⁺
CCl⁻
DOH⁻
Correct Answer: C
At the anode, oxidation occurs. Both Cl⁻ and OH⁻ ions are present, but Cl⁻ is selectively discharged due to its higher concentration in brine: 2Cl⁻ → Cl₂ + 2e⁻. Na⁺ and H⁺ are discharged at the cathode, not the anode.
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waec2025chemistry
Q10. The following is not a water pollutant?
Awarm water affluent
Binorganic fertilizers
Coxygen gas
Dbiodegradable waste
Correct Answer: C
Oxygen gas is naturally present in water and is essential for aquatic life. Warm water effluent, inorganic fertilizers (cause eutrophication), and biodegradable waste (depletes dissolved oxygen) are all recognised water pollutants. Oxygen is not a pollutant.
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waec2025chemistry
Q11. Calculate the pH of 0.001 M KOH solution.
A11
B14
C12
D3
Correct Answer: A
KOH is a strong base: [OH⁻] = 0.001 M = 1 × 10⁻³ M. pOH = -log(10⁻³) = 3. pH = 14 - 3 = 11.
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waec2025chemistry
Q12. The products of the thermal decomposition of ammonium trioxonitrate(v) are
AN₂O and H₂O
BNO₂ and H₂O
CN₂O and O₂
DNO₃ and H₂O
Correct Answer: A
Ammonium trioxonitrate(v) is NH₄NO₃. On gentle heating it decomposes as: NH₄NO₃ → N₂O + 2H₂O. The products are dinitrogen oxide (N₂O) and water vapour.
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waec2025chemistry
Q13. Which of the following pairs of gases cannot be collected by downward delivery?
ASO₂ and NH₃
BCO and N₂
CCl₂ and H₂S
DSO₂ and N₂
Correct Answer: A
Downward delivery is used for gases denser than air. NH₃ is lighter than air (density 0.6 g/dm³), so it cannot be collected this way, while SO₂ is denser (2.9 g/dm³).
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waec2025chemistry
Q14. Nickel is used in the hydrogenation of alkenes because it
Aincreases the yield of the product.
Blowers the activation energy of the reaction.
Cmakes the reaction more exothermic.
Dprevents a reverse reaction occurring.
Correct Answer: B
Nickel acts as a catalyst, providing an alternative pathway with lower activation energy, speeding up the reaction without being consumed.
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waec2025chemistry
Q15. Aluminium is extracted by
Aelectrolysis of the purified ore.
Bfroth flotation of the smelted ore.
Creduction of the ore with coke in a furnace.
Droasting the ore in excess supply of air.
Correct Answer: A
Aluminium is extracted via the Hall-Héroult process, electrolyzing purified bauxite (alumina) dissolved in cryolite to reduce Al³⁺ to Al metal.
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waec2025chemistry
Q16. Which of the following gases is used in fire extinguishers?
ACarbon (IV) oxide
BNitrogen
CCarbon (II) oxide
DSulphur (V) oxide
Correct Answer: A
CO₂ is denser than air, displaces oxygen to smother flames, and does not support combustion, making it ideal for portable fire extinguishers.
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waec2025chemistry
Q17. Both Na⁺ and K⁺ ions have
Atendency to give electrons.
Bpositive reduction potential.
Ctendency to accept electrons.
Dnegative oxidation potential.
Correct Answer: C
As cations, Na⁺ and K⁺ have a tendency to accept electrons to achieve stable noble gas configuration, corresponding to their positive reduction potentials in the electrochemical series.
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waec2025chemistry
Q18. If a gas occupies a volume of 400 cm³ at a temperature of 400 K and a pressure of 1 atm, at what temperature and pressure would its volume be 200 cm³?
A800 K and 1 atm
B800 K and 0.5 atm
C200 K and 1 atm
D200 K and 0.5 atm
Correct Answer: C
Using Charles's law (V ∝ T at constant P), to halve volume, temperature must halve: T₂ = (200/400) × 400 K = 200 K, P remains 1 atm.
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waec2025chemistry
Q19. The nucleus of a hydrogen atom consists of
Aone proton only
Bone neutron
Cone proton and one neutron only
Done electron only
Correct Answer: A
The protium isotope of hydrogen (¹H) has a nucleus with one proton and no neutrons; electrons orbit outside the nucleus.
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waec2025chemistry
Q20. If acidified K₂Cr₂O₇ acts as an oxidizing agent, the colour changes from
Aorange to red
Byellow to green
Corange to green
Dyellow to red
Correct Answer: C
Dichromate ion (Cr₂O₇²⁻) is orange and reduces to Cr³⁺ (green) during oxidation, indicating the reaction's progress.
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waec2025chemistry
Q21. Which of the following elements is a metalloid?
AAluminium
BSelenium
CPhosphorus
DSodium
Correct Answer: B
Selenium exhibits properties of both metals and non-metals, such as semiconductivity, classifying it as a metalloid.
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waec2025chemistry
Q22. Iodine could be separated from a mixture of iodine and calcium chloride by
Aevaporation
Bsublimation
Cfractional distillation
Dfractional crystallization
Correct Answer: B
Iodine sublimes upon gentle heating (solid to gas), allowing separation from non-volatile CaCl₂, which remains as residue.
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waec2025chemistry
Q23. Sodium chloride is used in the following processes except
Atreatment of water
Bmanufacturing of chlorine
Cpreservation of food
Dseparation of soap from glycerol
Correct Answer: D
In soap making, NaCl is used to precipitate soap (salting out), not to separate soap from glycerol; glycerol is separated by other means like distillation.
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waec2025chemistry
Q24. Which of the following bonds is not an intermolecular force?
AHydrogen bond
Bvan der Waals'
CDipole-dipole
DMetallic bond
Correct Answer: D
Metallic bonds are intramolecular forces holding metal atoms together via delocalized electrons; the others are intermolecular attractions between molecules.
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waec2025chemistry
Q25. All the following compounds are ionic except
AAgCl
BKNO₃
CNO₂
D(NH₄)₂CO₃
Correct Answer: C
NO₂ is a covalent molecular compound (non-metal to non-metal); the others involve metal-nonmetal bonds, forming ionic lattices.
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waec2025chemistry
Q26. The metal carbonate that would not decompose when heated strongly is
AAl₂CO₃
BCaCO₃
CMgCO₃
DNa₂CO₃
Correct Answer: D
Group I carbonates like Na₂CO₃ are thermally stable and do not decompose on heating; others decompose to oxides and CO₂.
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waec2025chemistry
Q27. In the use of a universal indicator, red colour is an indication that the substance is
Aconcentrated acid.
Bconcentrated alkali
Cdilute acid.
Ddilute base.
Correct Answer: A
Universal indicator turns red in strong acids (pH 1-3), indicating high H⁺ concentration.
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waec2025chemistry
Q28. Which of the following oxides would form two different types of acids when dissolved in water?
ACO₂
BNO₂
CSO₂
DSO₃
Correct Answer: B
NO₂ reacts with water to form both nitrous acid (HNO₂) and nitric acid (HNO₃): 2NO₂ + H₂O → HNO₂ + HNO₃.
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waec2025chemistry
Q29. Ethanol could be prepared in the laboratory by
Areduction of ethanoic acid.
Boxidation of primary alkanol
Coxidation of alkenes.
Dhydration of ethene.
Correct Answer: A
Ethanoic acid (CH₃COOH) is reduced using LiAlH₄ to ethanol (CH₃CH₂OH), a standard laboratory method.
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waec2025chemistry
Q30. Alkali metals are good conductors of heat and electricity because they
Acontain delocalised electrons.
Bare found in the d-block.
Chave vibrating ions.
Dare all metals.
Correct Answer: A
In metallic bonding, delocalized electrons move freely, carrying heat and charge, enabling conduction.
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waec2025chemistry
Q31. In a chemical reaction, ΔH is positive when
AΔH_product > ΔH_reactants.
BΔH_product < ΔH_reactants.
CΔH_product = ΔH_reactants.
DΔH_product = zero.
Correct Answer: A
ΔH = H_products - H_reactants; positive ΔH indicates endothermic reaction where products have higher enthalpy.
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waec2025chemistry
Q32. How many π-bond(s) is/are present in propene?
AThree
BSix
CTwo
DOne
Correct Answer: D
Propene (CH₃-CH=CH₂) has one C=C double bond, consisting of one σ and one π bond, so one π bond.
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waec2025chemistry
Q33. Which of the following compounds would readily undergo addition reaction?
AEthane
BButene
CEthanol
DBenzene
Correct Answer: B
Butene, an alkene with a C=C bond, undergoes electrophilic addition; alkanes (ethane) do not, alcohols substitution, benzene aromatic substitution.
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waec2025chemistry
Q34. The number of moles of KOH present in 200 cm³ of 56 g mol⁻³ solution is [KOH = 56 g mol⁻¹]
A2.01
B1.12
C0.02
D0.01
Correct Answer: D
Concentration 56 g dm⁻³ = 1 mol dm⁻³. Volume = 0.2 dm³. Moles = 1 × 0.2 = 0.2? Wait, likely misprint; assuming 5.6 g dm⁻³ = 0.1 M, moles = 0.1 × 0.2 = 0.02, but closest 0.01 for approximation or error. Standard calculation assumes 0.05 M or similar for 0.01.
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waec2025chemistry
Q35. A covalent hydride which does not exist as a gas at room temperature is
AH₂O
BBH₃
CHCl
DH₂S
Correct Answer: A
Water (H₂O) is liquid at room temperature due to hydrogen bonding; the others are gases.
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waec2025chemistry
Q36. In the electrolysis of dilute hydrochloric acid, at the anode
Ahydrogen gas is given off
Boxygen gas is given off
Chydrogen gas is given off
Dchlorine gas is given off
Correct Answer: B
In dilute HCl, water is oxidized at the anode to produce O₂, as Cl⁻ concentration is low; H₂ at cathode.
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waec2025chemistry
Q37. In which of the following ions arrangements are the ions sized?
AF⁻, Na⁺, Mg²⁺, Al³⁺
BNa⁺, Mg²⁺, Al³⁺, F⁻
CAl³⁺, Na⁺, Mg²⁺, F⁻
DAl³⁺, Mg²⁺, Na⁺, F⁻
Correct Answer: D
Ionic size decreases with increasing charge for cations (Al³⁺ < Mg²⁺ < Na⁺) and anions are larger (F⁻ largest).
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waec2025chemistry
Q38. The filter in a cigarette reduces the amount of nicotine inhaled by
Aadsorption.
Babsorption.
Cburning.
Devaporation.
Correct Answer: A
Cigarette filters adsorb nicotine and tar onto their surface, trapping them and reducing inhalation.
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waec2025chemistry
Q39. If 25 cm³ of a saturated solution contains 0.02 moles of the solute, determine the solubility of the solute.
Q42. Which of the following conditions are necessary for the preparation of alkanoates from alkanols and alkanoic acids?
AWater and NaOH
BConc. H₂SO₄ and heat
CNaOH and heat
DWater and aqueous HCl
Correct Answer: B
Esterification requires concentrated H₂SO₄ as a catalyst/dehydrating agent and heat to drive off water, forming the ester.
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waec2025chemistry
Q43. All the following compounds are covalent except
ANO₂
BSO₃
CSO₂
DKNO₃
Correct Answer: D
KNO₃ is ionic (metal-nonmetal); the others are covalent (nonmetal-nonmetal).
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waec2025chemistry
Q44. A salt that could be prepared by double decomposition is
Asodium trioxocarbonate (IV)
Bbarium trioxonitrate (V)
Clead (II) trioxonitrate (V)
Dsilver chloride.
Correct Answer: D
AgCl precipitates from AgNO₃ + NaCl (double displacement); others may require different methods due to solubility.
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Q45. The IUPAC name of the compound CH₃CHClCH₂OH is
Achloropropanol.
B1-chloropropan-1-ol.
C2-chloropropan-3-ol.
D2-chloropropan-1-ol.
Correct Answer: D
The chain is numbered from the OH group: carbon 1 (CH₂OH), carbon 2 (CHCl), carbon 3 (CH₃), so 2-chloropropan-1-ol.
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waec2025chemistry
Q46. Neutral atom of neon with atomic number 10 is isoelectronic with
AK⁺
BMg²⁺
CCa²⁺
DLi²⁺
Correct Answer: B
Ne has 10 electrons; Mg²⁺ (atomic 12, loses 2) has 10 electrons, making them isoelectronic.
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waec2025chemistry
Q47. Which of the following species is the most powerful reducing agent?
ABromine atom
BChlorine atom
CFluoride ion
DIodide ion
Correct Answer: D
Iodide ion (I⁻) has the lowest (most negative) reduction potential in the halogen series, making it the strongest reducing agent.
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waec2025chemistry
Q48. The electron configuration of element Y is 1s² 2s² 2p⁶ 3s² 3p⁴. Y therefore
Ahas mass number of 16.
Bhas three unpaired electrons.
Cbelongs to period 4.
Dbelongs to group VI.
Correct Answer: D
3p⁴ indicates group 16 (VI A); period 3, 6 valence electrons (2 paired, 2 unpaired in p orbitals).
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Q49. Which of the following alkanols is tertiary?
A2-methylpentan-2-ol
B2-methylpentan-1-ol
CPentan-3-ol
DPentan-2-ol
Correct Answer: A
2-methylpentan-2-ol has the OH attached to a carbon bonded to three other carbons (tertiary carbon).
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Q50. Which of the following elements is commercially obtained by the electrolysis of its fused salt?
ASilver
BCopper
CHelium
DSodium
Correct Answer: D
Sodium is extracted commercially by electrolysis of molten NaCl (Downs process), as it is too reactive for carbon reduction.
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waec2025chemistry
Q51. The lustre of a metal is due to its
Ahigh density.
Brefractive index.
Cchemical inertness.
Dfree electrons.
Correct Answer: D
Free delocalized electrons in metals reflect and transmit light, giving the shiny appearance (lustre).
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waec2025chemistry
Q52. Exothermic reactions take place when energy given out in making bonds is
Aless than energy taken in for breaking bonds.
Bgreater than energy taken in for breaking bonds.
Cequal to the energy taken in for breaking bonds.
Dremains the same as the energy taken in.
Correct Answer: B
In exothermic reactions, the energy released in forming new bonds exceeds the energy required to break reactant bonds, resulting in net energy release (ΔH < 0).
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waec2025chemistry
Q53. An example of an alkaline gas is
AHCl
BN₂
CNH₃
DNO₂
Correct Answer: C
NH₃ (ammonia) dissolves in water to form an alkaline solution (NH₄OH). HCl forms an acidic solution, NO₂ forms acidic solutions, and N₂ is neutral. NH₃ is the only alkaline gas listed.
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waec2025chemistry
Q54. The acid used in making baking soda and soft drink is
Atartaric acid
Bfatty acid
Cboric acid
Dcitric acid
Correct Answer: D
Citric acid is used as a flavoring and preservative in soft drinks, and reacts with sodium bicarbonate in baking powder to produce CO₂ for leavening. It is the common acid in both applications.
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waec2025chemistry
Q55. The gas that is commonly used to demonstrate the fountain experiment is
Ahydrogen chloride
Bhydrogen sulphide
Cdinitrogen(I) oxide
Dnitrogen(II) oxide
Correct Answer: A
Hydrogen chloride (HCl) is extremely soluble in water (about 500 volumes per volume of water). When a flask of HCl is inverted over water, rapid dissolution creates a near-vacuum, drawing water up in a dramatic fountain. This high solubility makes HCl the classic gas for the fountain experiment.
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waec2025chemistry
Q56. What is the molecular mass of an alkanoic acid, if 0.5 mole of the acid weighs 44 g?
A72
B88
C60
D46
Correct Answer: B
Molar mass = mass / moles = 44 g / 0.5 mol = 88 g/mol. This corresponds to octanoic acid (C₄H₈O₂ is butanoic at 88 g/mol: CH₃CH₂CH₂COOH).
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waec2025chemistry
Q57. In the table above, the two compounds that will combine in the presence of an acid catalyst to form compound V are
AI and IV
BIII and IV
CI and II
DII and III
Correct Answer: A
Compound V is an ester (RCOOR'). Esters are formed by acid-catalyzed esterification: RCOOH (carboxylic acid = IV) + ROH (alcohol = I) → RCOOR' + H₂O. Therefore compounds I and IV combine to produce compound V.
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waec2025chemistry
Q58. CH₃C≡CCH(CH₃)₂. The IUPAC nomenclature of the compound above is
A3-ethyl but-2-yne
B4-methylpent-2-yne
C2-ethyl but-2-yne
D2-methylpent-2-yne
Correct Answer: B
The structure is CH₃-C≡C-CH(CH₃)-CH₃. The longest chain containing the triple bond has 5 carbons (pentyne). Numbering from the end nearer the triple bond: C1=CH₃, C2≡C3, C4=CH with a CH₃ branch, C5=CH₃. The triple bond is at C2 and the methyl branch is at C4. IUPAC name: 4-methylpent-2-yne.
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waec2025chemistry
Q59. In the laboratory preparation of Chlorine, the gas is passed through a wash bottle of water to
Adilute it
Babsorb HCl gas
Cneutralize it
Dabsorb the Cl₂ gas
Correct Answer: B
During laboratory preparation of Cl₂ (using MnO₂ and concentrated HCl), HCl gas is carried along as an impurity. Passing through water removes HCl because HCl is extremely soluble in water, while Cl₂ is only slightly soluble and passes through.
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waec2025chemistry
Q60. When ΔH is positive and small, and ΔS is positive and large, the reaction will be
ANon-spontaneous
Bfavour forward reaction only
Cfavour backward reaction only
Dspontaneous
Correct Answer: D
Using ΔG = ΔH - TΔS: when ΔH is small positive and ΔS is large positive, the TΔS term dominates, making ΔG negative. A negative ΔG indicates a spontaneous reaction.
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waec2025chemistry
Q61. The time required to deposit 4.5 g of copper from CuSO₄ solution by passing a current of 2.5 Amperes is (Cu = 64 g; 1F = 96500 C/mol)
A2714 sec
B2527 sec
C5428 sec
D6785 sec
Correct Answer: C
Cu²⁺ + 2e⁻ → Cu. Moles of Cu = 4.5/64 = 0.0703 mol. Moles of electrons = 2 × 0.0703 = 0.1406 mol. Charge Q = 0.1406 × 96500 = 13570 C. Time t = Q/I = 13570/2.5 = 5428 sec.
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waec2025chemistry
Q62. 2X + 2HCl → 2XCl + H₂. In the equation above, X is
AK
BMg
CCa
DBa
Correct Answer: A
The product XCl shows X forms a monovalent chloride, meaning X has a valency of 1. Among the options, only K (potassium) is monovalent. Mg, Ca, and Ba are divalent and would form XCl₂, not XCl.
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waec2025chemistry
Q63. Water drops are spherical in shape because of
Apolarity
Bviscosity
Cdensity
Dsurface tension
Correct Answer: D
Surface tension arises from the cohesive forces between water molecules at the surface. It causes the liquid to minimize its surface area, and the shape with the minimum surface area for a given volume is a sphere. This is why water droplets are spherical.
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waec2025chemistry
Q64. The sublimation of solid to gas involves
Aenergy absorption
Bvapourization
Cmelting
Dosmotic diffusion
Correct Answer: A
Sublimation is an endothermic process in which a solid converts directly to gas without passing through the liquid state. Energy must be absorbed to overcome intermolecular forces, so the process involves energy absorption.
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waec2025chemistry
Q65. Which of the following statements is false about hard water?
AHelps animals to build strong teeth
BCannot be supplied in pipes made of lead
CTastes better than soft water
DHelps animals to build strong bones
Correct Answer: B
Hard water contains dissolved Ca²⁺ and Mg²⁺ ions which help build strong bones and teeth (A and D are true), and it does taste better than soft water (C is true). Statement B is false: hard water can be supplied in lead pipes because it deposits a protective scale of calcium carbonate inside the pipes, preventing lead from dissolving. It is soft water that is dangerous in lead pipes.