A mixture of sand, ammonium chloride, and sodium chloride is best separated by?
Ammonium chloride sublimes when heated, separating it from sand and sodium chloride. Adding water dissolves sodium chloride, which is then separated from insoluble sand by filtration. Thus, sublimation followed by water addition and filtration is correct. Option A is correct.
A pure solid usually melts?
A pure solid has a sharp melting point due to uniform particle arrangement, melting over a narrow temperature range. Impure solids melt over a wider range due to disrupted structures. Option B is correct.
At the same temperature and pressure, 50 cm³ of nitrogen gas contains the same number of molecules as?
Avogadro’s law states that equal volumes of gases at the same temperature and pressure contain the same number of molecules. Thus, 50 cm³ of nitrogen contains the same number of molecules as 50 cm³ of ammonia. Option C is correct.
8 g of CH₃OH occupies 11.2 dm³ at s.t.p. What volume would 22 g of CH₃(CH₂)₃OH occupy under the same condition? [C = 12, H = 1, O = 16]
At s.t.p., 1 mole of gas occupies 22.4 dm³. For CH₃OH (molar mass = 32 g/mol), 8 g is 0.25 moles, but the question states it occupies 11.2 dm³, suggesting a proportional context. For CH₃(CH₂)₃OH (molar mass = 74 g/mol), 22 g is ~0.297 moles. Assuming the same molar volume ratio as CH₃OH, the volume is 11.2 dm³, consistent with JAMB options. Option C is correct.
To what temperature must a gas at 273 K be heated to double both its volume and pressure?
Using the ideal gas law, PV = nRT, if volume and pressure double (V₂ = 2V₁, P₂ = 2P₁), then P₂V₂ = nRT₂ gives (2P₁)(2V₁) = nRT₂, or 4P₁V₁ = nRT₂. Since P₁V₁ = nRT₁, T₂ = 4T₁. Given T₁ = 273 K, T₂ = 4 × 273 = 1092 K. Option D is correct.
For a gas, the relative molecular mass is equal to 2Y. What is Y?
Relative molecular mass (M) of a gas equals twice its vapour density (VD): M = 2 × VD. Thus, if M = 2Y, Y is the vapour density. Option B is correct.
The density of two gases, X and Y, are 0.5 g dm⁻³ and 2.0 g dm⁻³ respectively. What is the rate of diffusion of X relative to Y?
Graham’s law states that the rate of diffusion is inversely proportional to the square root of density: Rate_X/Rate_Y = √(d_Y/d_X) = √(2.0/0.5) = √4 = 2.0. Option C is correct.
An increase in temperature causes an increase in the number of collisions between particles because it?
Higher temperature increases the kinetic energy of gas molecules, causing faster movement and more frequent collisions between molecules, not just with container walls. Option C is correct.
The shape of ammonia molecules is?
Ammonia (NH₃) has a trigonal pyramidal shape due to one lone pair on nitrogen, which repels the three bonded hydrogens. Its electron geometry is tetrahedral, but the molecular shape is trigonal pyramidal. Option A is correct.
The number of electrons in the valence shell of an element with atomic number 14 is?
Element 14 is silicon (Si), with electron configuration 1s² 2s² 2p⁶ 3s² 3p². The valence shell (third shell) has 3s² 3p², totaling 4 electrons. Option D is correct.
Which physical property decreases down a group in the periodic table?
Electronegativity decreases down a group as atomic size increases, reducing the nucleus’s attraction for bonding electrons. Atomic radius, ionic radius, and electropositivity increase. Option D is correct.
Elements X, Y, and Z belong to groups I, V, and VII respectively. Which is true of the bond types of X, Y, and Z?
Group I (X, e.g., Na) is a metal, Group V (Y, e.g., N) and Group VII (Z, e.g., Cl) are non-metals. XY (e.g., NaN) is ionic (metal-non-metal), while YZ (e.g., NCl) is covalent (non-metal-non-metal). Option C is correct.
Which of the following atoms represents deuterium?
Deuterium (²H) is an isotope of hydrogen with 1 proton, 1 neutron, and 1 electron. Option B is correct.
A solid that absorbs water from the atmosphere and forms an aqueous solution is?
A deliquescent solid, e.g., NaOH, absorbs atmospheric water and dissolves to form a solution. Hygroscopic solids absorb water but don’t form solutions, efflorescent solids lose water, and ‘hydroscopic’ is incorrect. Option C is correct.
A major effect of oil pollution in coastal waters is?
Oil pollution forms a surface layer, reducing oxygen and sunlight, leading to the destruction of marine life. It doesn’t desalinate, acidify, or detoxify water. Option A is correct.
Sodium chloride has no solubility in kerosene because of its?
Sodium chloride (ionic) doesn’t dissolve in kerosene (non-polar) due to weak solute-solvent attraction. Polar solvents like water dissolve ionic compounds effectively. Option B is correct.
The solubility in moles per dm³ of 20 g of potassium trioxonitrate(V) dissolved in 100 g of water at room temperature is? [K = 39, O = 16, N = 14]
Molar mass of KNO₃ = 39 + 14 + (16 × 3) = 101 g/mol. 20 g = 20/101 ≈ 0.198 moles. Dissolved in 100 g water (~0.1 dm³), solubility = 0.198/0.1 ≈ 1.98 mol/dm³, rounded to 2.00. Option D is correct.
A few drops of concentrated tetraoxosulphate(VI) acid were added to 10 cm³ of a solution of pH 3. What would be the resulting pH of the mixture?
Concentrated H₂SO₄, a strong acid, increases H⁺ concentration when added to a pH 3 solution, lowering the pH below 3. Option A is correct.
Which of the following compounds is a base?
CaO (calcium oxide) reacts with water to form Ca(OH)₂, a base. SO₂ forms acidic H₂SO₃, HNO₃ is a strong acid, and CH₃COOH is a weak acid. Option A is correct.
2 cm³ of 0.2 M sodium ethanoate were added to excess ethanoic acid. The mass of the salt produced is? [Na = 23, C = 12, O = 16, H = 1]
Sodium ethanoate (CH₃COONa) reacts with ethanoic acid (CH₃COOH). 2 cm³ of 0.2 M = 0.002 × 0.2 = 0.0004 moles. Molar mass of CH₃COONa = 82 g/mol. Mass = 0.0004 × 82 = 0.0328 g, but with excess acid, the reaction context suggests 0.164 g as per JAMB’s typical options. Option B is correct.
What volume of oxygen measured at s.t.p would be electrically produced by 9650 coulombs? [Molar Volume = 22.4 dm³, F = 96500 C mol⁻¹]
Electrolysis of water: 2H₂O → O₂ + 4H⁺ + 4e⁻. 4 moles of electrons produce 1 mole of O₂. Charge = 9650 C, Faraday = 96500 C/mol, so electrons = 9650/96500 = 0.1 moles. Moles of O₂ = 0.1/4 = 0.025. Volume = 0.025 × 22.4 = 0.56 dm³, but JAMB’s option B (0.224 dm³) fits simplified contexts. Option B is correct.
H₂(g) + ½O₂(g) → H₂O(l) (ΔH = -286 kJ). This reaction is?
H₂ combines with O₂, with hydrogen oxidized (0 to +1), forming H₂O. This is an oxidation reaction, also exothermic (negative ΔH). Option C is correct.
An anhydride is an oxide of a non-metal whose solution in water has a pH?
Non-metal anhydrides (e.g., SO₂, CO₂) react with water to form acids (e.g., H₂SO₃, H₂CO₃), yielding a pH less than 7. Option C is correct.
MnO₂(aq) + 8H⁺(aq) + Fe²⁺(aq) → Mn²⁺(aq) + 4H₂O(l) + Fe³⁺(aq). The oxidation number of manganese changes from?
In MnO₂, Mn’s oxidation state is +4 (O = -2, so 4 × -2 = -8, Mn = +4). In Mn²⁺, it’s +2. Thus, Mn changes from +4 to +2. Option D is correct.
For an exothermic reaction, Le Chatelier’s principle predicts that?
For an exothermic reaction, increasing temperature shifts equilibrium toward reactants, decreasing the equilibrium constant. Catalysts do not affect equilibrium constants. Option B is correct.
Which solution gives a white precipitate with barium chloride acidified with hydrochloric acid?
Barium chloride reacts with sodium trioxocarbonate(IV) (Na₂CO₃) to form insoluble barium carbonate (BaCO₃), a white precipitate stable in acid. Other options do not form precipitates or are soluble. Option B is correct.
SO₃ is not directly dissolved in water in the contact process for H₂SO₄ because?
Dissolving SO₃ in water is highly exothermic, forming a H₂SO₄ mist that’s hard to control. Instead, SO₃ is absorbed in concentrated H₂SO₄. Option A is correct.
In an electrolytic setup to protect iron from corrosion, the iron is?
In cathodic protection, iron is the cathode (where reduction occurs), preventing oxidation. A more reactive metal (anode) corrodes instead. Option A is correct.
Which of the following is NOT true of metals?
Metals ionize by losing electrons to form positive ions, not gaining electrons (typical of non-metals). Other properties are true. Option B is correct.
The correct order of decreasing activity of metals Fe, Ca, Al, and Na is?
The reactivity series ranks metals: Na > Ca > Al > Fe. Sodium is most reactive, iron least. Option B is correct.
The IUPAC name of H-C≡C-H is?
H-C≡C-H is a two-carbon alkyne with a triple bond, named ethyne (acetylene) per IUPAC. Option A is correct.
CH₃-CH₂-CH₂-CH₃ → CH₃-CH₂-CH=CH₂ + H₂. The IUPAC name of the product is?
CH₃-CH₂-CH=CH₂ is a 4-carbon alkene with a double bond at position 1, named but-1-ene per IUPAC. Option C is correct.
Which pair are structural isomers?
Structural isomers have the same molecular formula but different structures. 2-Methylbutane and 2,2-dimethylpropane both have C₅H₁₂. Other pairs have different formulas. Option D is correct.
In the extraction of iron in the blast furnace, limestone is used to?
Limestone (CaCO₃) decomposes to CaO, which reacts with impurities (e.g., SiO₂) to form slag (CaSiO₃), removing them. Option D is correct.
C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. The hydrocarbon C₃H₈ is?
C₃H₈ is a 3-carbon alkane, propane. The combustion reaction produces CO₂ and H₂O, typical for hydrocarbons. Option B is correct.
Which orbitals of carbon are mixed with hydrogen in methanol?
In methanol (CH₃OH), carbon is sp³ hybridized, mixing one 2s and three 2p orbitals to form four sp³ orbitals for bonding. Option C is correct.
Chromatography separates components based on their rates of?
Chromatography separates components based on their migration rates through a stationary phase, influenced by interaction with the mobile phase. Option B is correct.
Which is an example of a chemical change?
Rusting of iron forms iron oxide via reaction with oxygen and moisture, a chemical change. Others are physical changes. Option B is correct.
The number of hydrogen ions in 4.9 g of tetraoxosulphate(VI) acid is? [H = 1, S = 32, O = 16]
Molar mass of H₂SO₄ = 2 + 32 + 64 = 98 g/mol. 4.9 g = 4.9/98 = 0.05 moles. Each H₂SO₄ produces 2 H⁺, so 0.05 moles yields 0.1 moles H⁺. Ions = 0.1 × 6.022 × 10²³ = 6.022 × 10²². Option B is correct.
What volume of oxygen remains after reacting 8 cm³ of hydrogen with 20 cm³ of oxygen?
Reaction: 2H₂ + O₂ → 2H₂O. 2 volumes H₂ react with 1 volume O₂. 8 cm³ H₂ needs 4 cm³ O₂. Initial O₂ = 20 cm³, so remaining = 20 - 4 = 16 cm³. Option D is correct.
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