Which of the following substances is not a homogeneous mixture?
A homogeneous mixture has a uniform composition throughout. Filtered sea water, soft drinks, and writing ink are homogeneous as their components are evenly distributed. Flood water is heterogeneous due to suspended particles like mud, making it non-uniform.
There is a large temperature interval between the melting point and boiling point of a metal because
In metals, melting disrupts the lattice but the metallic bond (delocalized electrons) persists in the liquid state. Boiling requires breaking these bonds to vaporize the metal, needing much more energy, hence the large temperature interval.
How many moles of H⁺ ions are present in 1 dm³ of a 0.5 mol/dm³ solution of H₂SO₄?
H₂SO₄ is diprotic, releasing 2 H⁺ per molecule. For 0.5 mol/dm³ H₂SO₄ in 1 dm³, moles of H₂SO₄ = 0.5. Thus, moles of H⁺ = 0.5 × 2 = 1.0 mole.
In the reaction 2H₂S(g) + 3O₂(g) → 2H₂O(l) + 2SO₂(g), how many moles of O₂ are required to react with 4 moles of H₂S?
The balanced equation shows 2 moles of H₂S react with 3 moles of O₂. For 4 moles of H₂S: (3/2) × 4 = 6 moles of O₂ are required.
A gas occupies 2 dm³ at 300 K and 1 atm. At what temperature will its volume double if the pressure remains constant?
Using Charles’s Law (V₁/T₁ = V₂/T₂), V₁ = 2 dm³, T₁ = 300 K, V₂ = 4 dm³. T₂ = (V₂/V₁) × T₁ = (4/2) × 300 = 600 K.
If 100 cm³ of oxygen gas diffuses through a porous plug in 50 seconds, how long will it take for 100 cm³ of hydrogen gas to diffuse through the same plug? [Molar mass of O₂ = 32 g/mol, H₂ = 2 g/mol]
Using Graham’s Law: t₂/t₁ = √(M₂/M₁). For O₂, t₁ = 50 s, M = 32; for H₂, M = 2. t₂/50 = √(2/32) = √(1/16) = 1/4. Thus, t₂ = 50 × (1/4) = 12.5 s.
Which of the following is a measure of the average kinetic energy of the molecules of a substance?
According to the kinetic theory of gases, the average kinetic energy of molecules is directly proportional to the absolute temperature (in Kelvin): KE = (3/2)kT.
An increase in temperature causes an increase in the pressure of a gas in a fixed volume due to an increase in the
Increasing temperature increases the kinetic energy of gas molecules, causing them to move faster and collide more frequently with the container walls, thus increasing pressure.
The nucleus of the isotope ²³⁸₉₂U contains
For ²³⁸₉₂U, the atomic number (92) is the number of protons, and the mass number (238) is the sum of protons and neutrons. Neutrons = 238 - 92 = 146.
How many lone pairs of electrons are present on the central atom of the H₂O molecule?
In H₂O, oxygen has 6 valence electrons. It forms 2 bonds with hydrogen (using 2 electrons), leaving 4 electrons as 2 lone pairs on the oxygen atom.
In the nuclear reaction ⁷₃Li + ¹₁H → ⁴₂He + X, what is X?
Balancing the reaction: ⁷₃Li + ¹₁H → ⁴₂He + X. Mass numbers: 7 + 1 = 4 + X, so X’s mass = 4. Atomic numbers: 3 + 1 = 2 + X, so X’s atomic number = 2. Thus, X is ⁴₂He.
The elements P, Q, R, and S have 1, 2, 3, and 7 electrons in their outermost shells, respectively. Which element is most likely to be a metal?
Elements with 1-3 valence electrons tend to be metals, as they lose electrons to form positive ions. R, with 3 valence electrons, is most likely a metal (e.g., aluminum in Group 13).
The pollutants that are likely to be present in an industrial environment are
Industrial processes often emit H₂S (from sulfur compounds), SO₂ (from burning sulfur-containing fuels), and CO/CO₂ (from combustion), making these the most likely pollutants.
Which of the following gases dissolves in water vapor to produce acid rain during rainfall?
Sulphur(IV) oxide (SO₂) dissolves in water vapor to form sulfurous acid (H₂SO₃), which can oxidize to sulfuric acid (H₂SO₄), contributing to acid rain.
Water in a town supply is chlorinated to make it free from
Chlorination is used in water treatment to kill bacteria and disinfect the water, ensuring it is safe for consumption.
On which of the following does the solubility of a gaseous substance depend? I. Nature of solvent. II. Temperature. III. Pressure. IV. Nature of solute.
Gas solubility depends on the nature of the solvent and solute (chemical compatibility), temperature (solubility decreases with increasing temperature), and pressure (Henry’s Law: solubility increases with pressure).
An aqueous solution consists of
An aqueous solution is a solution where the solvent is water, and the solute (which can be solid, liquid, or gas) is dissolved in it.
A sample of orange juice has a pH of 3.80. What is the concentration of hydroxide ions in the juice? [Kw = 1.0 × 10⁻¹⁴ at 25°C]
pH = 3.80, so [H⁺] = 10⁻³.⁸⁰ ≈ 1.58 × 10⁻⁴ M. Using Kw = [H⁺][OH⁻], [OH⁻] = 1.0 × 10⁻¹⁴ / 1.58 × 10⁻⁴ ≈ 6.3 × 10⁻¹¹ M.
Arrange the following compounds in order of increasing acidity (weakest to strongest): CH₃OH, C₆H₅CH₃, CH₃COOH, HCl.
C₆H₅CH₃ (toluene) has no acidic protons. CH₃OH (methanol, pKa ~15) is a weak acid. CH₃COOH (acetic acid, pKa ~4.76) is stronger. HCl is a strong acid (pKa ~ -7). Order: C₆H₅CH₃ < CH₃OH < CH₃COOH < HCl.
Which of the following is an acid salt?
An acid salt contains a replaceable hydrogen ion. NaHSO₄ has one H⁺ that can be replaced, making it an acid salt. A is a double salt, B and C are basic salts.
How many grams of H₂SO₄ are required to prepare 0.350 dm³ of a 6.00 mol/dm³ H₂SO₄ solution? [Molar mass of H₂SO₄ = 98 g/mol]
Moles of H₂SO₄ = 6.00 × 0.350 = 2.1 moles. Mass = moles × molar mass = 2.1 × 98 = 205.8 g ≈ 206 g.
During the electrolysis of CuSO₄ solution using carbon electrodes, what are the products at the anode and cathode, respectively?
At the cathode, Cu²⁺ + 2e⁻ → Cu (copper deposits). At the anode, 2H₂O → O₂ + 4H⁺ + 4e⁻ (oxygen gas is produced). Thus, oxygen at the anode, copper at the cathode.
Calculate the mass of magnesium produced by the electrolysis of MgCl₂ in a cell operating at 500 A for 24 hours. [Molar mass of Mg = 24 g/mol, F = 96500 C/mol]
Charge Q = I × t = 500 × (24 × 3600) = 43,200,000 C. For Mg²⁺, n = 2. Mass = (Q × M) / (n × F) = (43,200,000 × 24) / (2 × 96500) ≈ 107.7 g ≈ 108 g.
In the reaction MnO₄²⁻ + 2Cl⁻ + 4H⁺ → Mn²⁺ + Cl₂ + 2H₂O, the change in oxidation number of manganese is
In MnO₄²⁻, Mn is +6 (4O at -2 = -8, so +6 - 8 = -2). In Mn²⁺, Mn is +2. Change in oxidation number: +6 to +2 (a decrease of 4, indicating reduction).
In which of the following reactions does the entropy change (ΔS) for the forward reaction equal the negative of the entropy change for the backward reaction?
For a reversible reaction, ΔS_forward = -ΔS_backward. In B, Cu²⁺ + Fe → Fe²⁺ + Cu, the number of particles and phases remains the same (all in aqueous/solid states), so entropy changes are minimal and reversible. Other reactions involve gases with significant entropy changes.
For the reaction A → B, the enthalpy change for the forward reaction is +50 kJ/mol. What is the enthalpy change for the backward reaction?
For a reversible reaction, ΔH_forward = -ΔH_backward (Hess’s Law). If ΔH_forward = +50 kJ/mol, then ΔH_backward = -50 kJ/mol.
For the reaction A ⇌ B, how is the equilibrium constant for the forward reaction related to that of the backward reaction?
For A ⇌ B, K_forward = [B]/[A], K_backward = [A]/[B]. Thus, K_forward × K_backward = ([B]/[A]) × ([A]/[B]) = 1.
Which of the following equilibria shows no net shift when the volume of the system is decreased?
Decreasing volume increases pressure, shifting equilibrium to the side with fewer gas moles (Le Chatelier’s principle). In A, 2 moles of gas (H₂ + I₂) form 2 moles (2HI), so there’s no shift. Other reactions have unequal gas moles on each side.
For the general reaction xP + yQ ⇌ mR, the expression for the equilibrium constant is
The equilibrium constant Kc for xP + yQ ⇌ mR is [R]^m / ([P]^x [Q]^y), where the coefficients become the powers of the concentrations.
Which of the following statements is true about carbon(IV) oxide (CO₂)?
CO₂ does not support combustion, forms a weak acid (H₂CO₃) in water, and has low solubility. However, magnesium burns in CO₂: 2Mg + CO₂ → 2MgO + C, producing magnesium oxide.
In the preparation of ammonia gas, a mixture of ammonium chloride and calcium hydroxide is heated. What gas is produced?
Heating NH₄Cl with Ca(OH)₂ produces ammonia: 2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2H₂O + 2NH₃.
Which of the following combinations of gases is used for metal welding?
Oxy-acetylene welding uses oxygen and ethyne (acetylene, C₂H₂) to produce a high-temperature flame for welding metals.
Which of the following oxides of nitrogen is unstable in air?
NO (nitric oxide) is unstable in air as it reacts with oxygen to form NO₂: 2NO + O₂ → 2NO₂. The other oxides are more stable under normal conditions.
The gas formed when ammonium trioxonitrate(V) is heated with sodium hydroxide is
NH₄NO₃ + NaOH → NaNO₃ + H₂O + NH₃. The gas produced is ammonia (NH₃).
Safety matches contain sulphur and
Safety matches contain sulfur and potassium chlorate (KClO₃), which acts as an oxidizing agent to support combustion when struck.
Addition of an aqueous solution of barium chloride to an aqueous solution of a salt produces a white precipitate. The salt is likely to be
BaCl₂ forms a white precipitate with sulfate ions: Ba²⁺ + SO₄²⁻ → BaSO₄ (insoluble). Nitrates, chlorides, and sulfides do not form white precipitates with BaCl₂ in this context.
Sodium hydroxide solution can be conveniently stored in a container made of
NaOH reacts with lead, zinc, and aluminum to form soluble complexes or hydrogen gas. Copper does not react with NaOH, making it suitable for storage.
Which of the following is NOT used as a raw material in the Solvay process for producing sodium carbonate?
The Solvay process uses NaCl, CaCO₃, and NH₃ to produce Na₂CO₃. Sodium carbonate is the product, not a raw material.
Duralumin is an alloy consisting of aluminum and
Duralumin is an alloy of aluminum, copper, magnesium, and manganese, used for its strength. The closest option is copper and magnesium.
In the reaction CaO + H₂O → Ca(OH)₂, the process is known as
The reaction of CaO (quicklime) with water to form Ca(OH)₂ (slaked lime) is called slaking, commonly used in the production of lime.
Now practice in exam mode
You've studied the answers — now test yourself under real exam conditions with the timer running.
Start JAMB Chemistry 2020 Quiz