How many electrons are transferred in reducing one Mn atom in the reaction MnO2 + 4HCl → MnCl2 + 2H2O + Cl2?
Manganese in MnO2 has an oxidation state of +4 and in MnCl2 has +2. The change (4 - 2 = 2) indicates 2 electrons are transferred per Mn atom.
20 cm³ of 0.1 M NH4OH is neutralized with 20.05 cm³ of 0.1 M HCl, liberating 102 J. What is the heat of neutralization?
Moles of NH4OH = 0.1 × 0.02 = 0.002 mol. Heat liberated = 102 J. ΔH = -102 / 0.002 = -51000 J/mol = -51.0 kJ mol⁻¹ (exothermic, hence negative).
What is the effect of increasing pressure on the equilibrium ZnO(s) + H2(g) ⇌ Zn(s) + H2O(l)?
H2 (gas) is on the left, and no gases are on the right. Increasing pressure favors the side with fewer gas moles, shifting the equilibrium to the right.
What is the volume of air containing 10 cm³ of oxygen?
Air contains approximately 20% oxygen by volume. To get 10 cm³ of oxygen, the volume of air required is 10 / 0.2 = 50 cm³.
The reaction Mg + H2O → MgO + H2 occurs with
Magnesium reacts with steam to form magnesium oxide (MgO) and hydrogen gas (H2), but does not react significantly with cold or hot water.
Steam passed over red-hot carbon produces
The reaction C + H2O → CO + H2 (water-gas shift reaction) produces carbon monoxide and hydrogen.
Which set contains an efflorescent, deliquescent, and hygroscopic substance, respectively?
Na2CO3·10H2O loses water to air (efflorescent), FeCl3 absorbs water and dissolves (deliquescent), H2SO4 absorbs water vapor (hygroscopic).
Exhaust from high-sulphur petrol contains
Combustion of high-sulphur petrol produces carbon monoxide (CO) and sulphur dioxide (SO2) as primary pollutants.
Oxygen-demanding wastes pollute water by
Oxygen-demanding wastes consume dissolved oxygen during decomposition, reducing oxygen available for aquatic organisms.
Which pair can form a higher oxide with oxygen?
SO2 can form SO3, and NO can form NO2. Other pairs do not form higher oxides (e.g., CO2 and H2O are stable).
Gas X turns wet lead ethanoate paper black, and gas Y bleaches litmus paper. The elements in X and Y are
Gas X is H2S (forms black PbS with lead ethanoate), and gas Y is Cl2 (bleaches litmus). Elements: H, S (in H2S); Cl (in Cl2).
Which sulphide is insoluble in dilute HCl?
CuS has a very low solubility product and remains insoluble in dilute HCl, unlike Na2S, ZnS, and FeS.
Chlorine in water with sunlight evolves
In sunlight, Cl2 reacts with water: Cl2 + H2O → 2HCl + ½O2, evolving oxygen gas.
Which metal does not form a stable trioxocarbonate(IV)?
Aluminium does not form stable carbonates due to its high charge density; Fe, Zn, and Pb form stable carbonates.
A compound Z reacts with NaOH to form a salt and water, with HCl to form a gas, and with H2SO4 to form a yellow suspension. Z is
Na2SO3 reacts with NaOH to form a salt, with HCl to form SO2 gas, and SO2 with H2SO4 forms sulphur (yellow suspension).
Ammonia is dried using
Calcium oxide (CaO) is used to dry ammonia as it does not react with it, unlike H2SO4, CaCl2, or MgSO4.
In the reaction xCu + yHNO3 → xCu(NO3)2 + 4H2O + zNO, the coefficients x, y, z are
Balanced equation: 3Cu + 8HNO3 → 3Cu(NO3)2 + 4H2O + 2NO. Thus, x = 3, y = 8, z = 2.
Fe2O3 in bauxite is removed by
Fe2O3 is insoluble in NaOH, while Al2O3 dissolves. Filtration removes Fe2O3 in the Bayer process.
A white solid, possibly Pb(NO3)2, ZnCO3, or CaCO3, when heated, leaves a residue that is yellow when hot and white when cold. It is
ZnCO3 decomposes to ZnO + CO2. ZnO is yellow when hot and white when cold, matching the description.
Which compound gives a lilac flame and forms a white precipitate with BaCl2?
K2SO4 contains K⁺ (lilac flame) and SO4²⁻ (forms insoluble BaSO4 with BaCl2).
A metal that is explosive with air and acids is extracted by
Reactive metals like sodium are extracted by electrolysis of their fused salts (e.g., NaCl), as they react explosively with air and acids.
Which statement is incorrect about the organic compound?
Glucose does not react with Na2CrO4. A: Butanoic acid reacts with Na2CO3 to release CO2. C: But-2-ene reduces KMnO4. D: Esterification forms a sweet-smelling ester.
An anti-knock agent in engines is
Lead tetraethyl was historically used as an anti-knock agent to improve fuel combustion in engines.
Palm oil reacting with potash to form foam undergoes
Saponification is the reaction of fats (like palm oil) with an alkali (potash) to form soap, which produces foam.
How many isomers does C3H8O have?
C3H8O has three isomers: propan-1-ol, propan-2-ol, and methyl ethyl ether.
Ethanol with excess H2SO4 at 170°C forms
Concentrated H2SO4 at 170°C dehydrates ethanol (C2H5OH) to form ethene (C2H4) by removing water.
Which is not formed by the reaction of Cl2 with CH4?
Chlorination of methane (CH4) produces CH3Cl, CH2Cl2, CHCl3, and CCl4. C2H5Cl (ethyl chloride) is not formed.
The general formula of an alkyl halide is
Alkyl halides have the formula CnH2n+1X, where X is a halogen (e.g., CH3Cl).
Which are made by polymerization?
Nylon and rubber are polymers formed by polymerization. Soap and margarine involve other processes (saponification, hydrogenation).
Starch is converted to ethanol by
Fermentation converts starch to ethanol through enzymatic breakdown and yeast action.
Co(II), Cu(II), and Fe ions in ink are separated by
Chromatography is used to separate metal ions based on their differential migration rates.
Which is a mixture?
Sea-water is a mixture of water, salts, and other substances. Sugar, NaCl, and iron filings are pure substances.
How many CO2 molecules are produced from 10.0 g CaCO3 reacting with 0.2 dm³ of 1 M HCl? [Ca=40, C=12, O=16, NA=6.02×10²³]
Molar mass of CaCO3 = 100 g/mol. Moles CaCO3 = 10/100 = 0.1 mol. Moles HCl = 0.2 × 1 = 0.2 mol. Reaction: CaCO3 + 2HCl → CaCl2 + CO2 + H2O. HCl is limiting (0.2 mol HCl produces 0.1 mol CO2). Molecules = 0.1 × 6.02×10²³ = 6.02×10²².
What is the mass of C2H2 produced from CaC2 + 2H2O at STP? [C=12, Ca=40, GMV=22.4 dm³]
Reaction: CaC2 + 2H2O → C2H2 + Ca(OH)2. Molar mass of C2H2 = 26 g/mol. At STP, 1 mol C2H2 = 22.4 dm³ ≈ 26 g. Thus, mass ≈ 2.6 g.
If the amount of O2 in 2.76 L at 0.825 atm and 300 K is halved, what is the new pressure?
Using PV = nRT, if the number of moles (n) is halved, and V and T remain constant, P is halved: 0.825 / 2 = 0.413 atm.
Which compound has the lowest vapour density? [O=16, Cl=35.5, H=1, C=12]
Vapour density = molar mass / 2. Ethanoic acid (60/2 = 30), Propanol (60/2 = 30), Dichloromethane (85/2 = 42.5), Ethanal (44/2 = 22). Ethanal has the lowest.
The rate of gaseous diffusion is related to density (d) by
Graham’s law states that the rate of diffusion (r) is inversely proportional to the square root of density: r = k/√d.
An isotope with atomic number 17 and mass number 36 has
Atomic number = 17 (protons). Mass number = 36. Neutrons = 36 - 17 = 19.
The bond between elements X (atomic number 12) and Y (atomic number 9) is
Element X (Mg, atomic number 12) and Y (F, atomic number 9) form MgF2, an ionic compound due to the large electronegativity difference.
Element Z has isotopes: 90% ¹⁶Z and 10% ¹⁸Z. What is the relative atomic mass?
Relative atomic mass = (0.9 × 16) + (0.1 × 18) = 14.4 + 1.8 = 16.2.
Now practice in exam mode
You've studied the answers — now test yourself under real exam conditions with the timer running.
Start JAMB Chemistry 2010 Quiz