2025. CBT WAEC GCE CHEMISTRY QUESTIONS
2025. CBT WAEC GCE CHEMISTRY QUESTIONS BELOW
2025. CBT WAEC GCE CHEMISTRY SOLUTIONS BELOW
*WAEC GCE CHEMISTRY*
(1a)
(i) Law of Conservation of Mass
(ii) Law of Definite Proportions
(iii) Law of Multiple Proportions
(1b)
A standard solution is a solution whose concentration is accurately known.
(1c)
(i) Iodine molecules have stronger intermolecular forces (van der Waals forces) than bromine molecules.
(ii) Iodine has a larger molecular size and mass than bromine.
(iii) More energy is required to separate iodine molecules, making it a solid, while bromine needs less energy and remains a liquid.
(1d)
Dalton’s Law states that the total pressure of a mixture of non reacting gases is equal to the sum of the partial pressures of the individual gases.
(1e)
(PICK ANY TWO)
(i) Intermolecular forces exist between gas molecules.
(ii) Gas particles have finite volume.
(iii) Collisions between gas particles are not perfectly elastic.
(1fi)
(PICK ANY ONE)
(i) It is largely covalent in nature.
(ii) It does not contain free or mobile ions.
(iii) It involves electron sharing instead of electron transfer.
(iv) The ions are strongly held and cannot move freely.
(1fii)
(PICK ANY TWO)
(i) High charge density of Al³⁺ ion.
(ii) Small ionic radius of aluminium.
(iii) Strong polarization of chloride ions.
(iv) Formation of covalent molecules instead of ionic ions.
(v) Electron sharing forms a molecular structure
(1gi)
Sodium (Na)
Magnesium (Mg)
(1gii)
Phosphorus (P)
Sulphur (S)
(1h)
(PICK ANY TWO)
(i) Manufacture of plastics (e.g. polyethene).
(ii) Production of synthetic rubber.
(iii) Used as raw materials in petrochemical industries.
(iv) Manufacture of alcohols (e.g. ethanol from ethene).
(v) Used in making detergents.
(1i)
=SIMILARITY=
(i) Both involve sharing of electrons between atoms.
=DIFFERENCE=
(i) In a covalent bond, each atom contributes electrons, while in a dative bond the shared pair is supplied by only one atom.
(1j)
(i) Oxidizing agent: Cl₂
(ii) Product of reduction: Cl⁻
(2ai)
A transition element is a d-block element that has an atom or ion with an incomplete d-subshell.
(2aii)
(α) Coloured compound formation: Transition metals form coloured compounds due to d-d electron transitions within the partially filled d-orbitals when they absorb certain wavelengths of light.
(β) Complex ion formation: Transition metals can form complex ions by bonding with ligands due to their ability to use empty d orbitals for coordinate covalent bonding.
(γ) Catalytic abilities: Transition metals act as catalysts because they can change oxidation states easily and provide a surface for reactants to adsorb, lowering activation energy.
(2bi)
(α) Potassium and oxygen: K₂O
(β) Sulphur and aluminium: Al₂S₃
(γ) Nitrogen and magnesium: Mg₃N₂
(2bii)
K₂O: Potassium oxide
Al₂S₃: Aluminium sulphide
Mg₃N₂: Magnesium nitride
(2ci)
(α) Atom
An atom is the smallest particle of an element that can exist alone and retains the chemical properties of that element; it consists of a nucleus (protons and neutrons) surrounded by electrons.
(β) Molecule
A molecule is a neutral group of two or more atoms chemically bonded together, representing the smallest particle of a substance that can exist while retaining its chemical identity.
(γ) Ion
An ion is an atom or group of atoms that has acquired a net electrical charge by losing or gaining electrons.
(2cii)
Atom: Cl (chlorine atom)
Molecule: Cl₂ (chlorine molecule)
Ion: Cl⁻ (chloride ion)
*CHEMISTRY SOLUTIONS*
(3ai)
Hydrochloric acid with zinc metal
Zn + 2HCl -> ZnCl₂ + H₂
(ii) Hydrochloric acid with zinc oxide
ZnO + 2HCl -> ZnCl₂ + H₂O
(iii) Hydrochloric acid with zinc trioxocarbonate(IV) (“zinc trioxocarbonate(IV)” = zinc carbonate, ZnCO3)
ZnCO₃ + 2HCl -> ZnCl₂ + CO₂ + H₂O
(3b)
Moles of sodium (Na):
moles Na = (4.6g) /23g mol⁻¹ = 0.2 mol
Number of atoms in 4.6 g Na:
atoms = 0.2 mol × 6.02 × 10²³ atoms mol⁻¹ = 1.204 × 10²³ atoms
Moles of H₂ required = (1.204 × 10²³)/ (6.02 × 10²³) = 0.2 mol.
molar mass of H₂ = 2g mol⁻¹.
mass of H₂ = 0.2mol × 2g mol⁻¹ = 0.4 g
(3c)
(i) Hydration (addition of water)
(ii) Concentrated H₂SO₄(sulphuric acid)
(iii) Presence of acid catalyst and suitable temperature
(iv) Propene: CH₃-CH=CH₂
Product C₃H₈O (major): CH₃-CH(OH)-CH₃
(v) Chemical equation (hydration, showing catalyst):
CH₃CH=CH₂ + H₂O —> CH₃CH(OH)CH₃ (H₂SO₄ to be written at the top of the arrow)
(vi) 2‑Propanol (propan‑2‑ol)
*WAEC GCE CHEMISTRY*
(5a)
(i)2NaOH + Cl_2 NaCl + NaClO + H2O
(ii)Cl_2 + H2O HOCl + HCl
(5aii)
(I)Chlorine: Gas
(II) Fluorine: Gas
(III) Astatine: Solid
(5aiii)
The strength of Van der Waal’s forces increases down the group due to the increase in atomic size and polarizability.
(5bi)
(i)Low temperature
(ii)High pressure
(5bii)
The choice of conditions is governed by Le Chatelier’s principle, which states that a system at equilibrium will adjust to counteract any changes in concentration, temperature, or pressure.
(5biii)
(i) For fertilizer production.
(ii)For cleaning agent
(iii)For Industrial applications
(5ci)
(i)High electrical conductivity
(ii)Ductility
(iii)Resistance to corrosion
(5cii)
(i)Oxidizing properties.
(ii)Antimicrobial activity.
(5di)
(i)For Construction.
(ii)It is use as an food and nutrition for humans.
(iii)It is use for manufacturing products, including paper, glass, and ceramics.
(5dii)
(i)Coke
(ii)Coal tar
OBJECTIVE QUESTIONS AND ANSWERS BELOW
