What is the oxidation number of sulfur in H₂SO₄?
In H₂SO₄, H = +1, O = -2. For a neutral molecule: 2(+1) + x + 4(-2) = 0 → 2 + x - 8 = 0 → x = +6. Sulfur’s oxidation number is +6.
What is the concentration of a solution containing 2g of NaOH in 100cm³ of solution? [Na = 23, O = 16, H = 1]
Molar mass of NaOH = 40 g/mol. Moles = 2/40 = 0.05 mol. Volume = 100 cm³ = 0.1 dm³. Concentration = 0.05/0.1 = 0.50 mol dm⁻³.
Which of the following properties is NOT peculiar to matter?
Random motion decreases from gas to solid due to increased orderliness.
The principle of column chromatography is based on the ability of the constituents to
Column chromatography separates components based on their differing rates of movement.
Which of the following is a characteristic of an ideal gas?
Ideal gases obey the ideal gas law, PV = nRT, assuming negligible volume and no intermolecular forces.
Which of the following statements is correct about the periodic table?
Valence electrons increase across a period as atomic number increases.
The relative atomic mass of a naturally occurring lithium consisting of 90% ⁷Li and 10% ⁶Li is
R.A.M = (0.9 × 7) + (0.1 × 6) = 6.3 + 0.6 = 6.9.
An isotope has an atomic number of 15 and a mass number of 31. The number of protons it contains is
Atomic number equals the number of protons, which is 15.
The molecular lattice of iodine is held together by
Iodine molecules are held together by weak van der Waal's forces in its lattice.
The arrangement of particles in crystal lattices can be studied using
X-rays are used in X-ray diffraction to study crystal lattice structures.
The solubility of a solute is 0.6 mol dm⁻³ at 55°C and 0.5 mol dm⁻³ at 40°C. How much solute is deposited when 200 cm³ of the solution is cooled from 55°C to 40°C?
Solubility difference = 0.6 - 0.5 = 0.1 mol dm⁻³. Volume = 200 cm³ = 0.2 dm³. Solute deposited = 0.1 × 0.2 = 0.02 mol.
The importance of sodium aluminate (III) in the treatment of water is to
Sodium aluminate promotes coagulation, aiding in water purification.
What type of bond exists between an element with atomic number 12 and an element with atomic number 17?
Element 12 (Mg) and element 17 (Cl) form MgCl₂ via ionic bonding.
Hardness of water is mainly due to the presence of
Ca(HCO₃)₂ or CaSO₄ causes water hardness.
A suitable solvent for iodine and naphthalene is
Ethanol effectively dissolves both iodine and naphthalene.
Which of the following noble gases is commonly found in the atmosphere?
Argon is the most abundant noble gas in the atmosphere.
N₂O₄(g) ⇌ 2NO₂(g) ∆H = +ve. In the reaction above, an increase in temperature will
Endothermic reaction: higher temperature increases K, shifting equilibrium right.
CH₃COOH(aq) + OH⁻(aq) ⇌ CH₃COO⁻(aq) + H₂O(l). In the reaction above, CH₃COO⁻(aq) is
CH₃COO⁻ is the conjugate base of CH₃COOH after losing H⁺.
How many cations will be produced from a solution of potassium aluminium tetraoxosulphate (VI)?
KAl(SO₄)₂ → K⁺ + Al³⁺ + 2SO₄²⁻; produces 2 cations (K⁺, Al³⁺).
Which of the following is NOT an alkali?
NH₃ is a weak base, not an alkali; others are soluble hydroxides.
An effect of thermal pollution on water bodies is the
Thermal pollution reduces dissolved oxygen, affecting aquatic life.
Which of the following is a deliquescent compound?
CaCl₂ absorbs moisture to form a solution, making it deliquescent.
A chemical reaction where the hydration energy is greater than the lattice energy is referred to as
Hydration energy > lattice energy releases heat, making it exothermic.
The function of zinc electrode in a galvanic cell is that it
Zinc undergoes oxidation, producing electrons at the anode.
CH₄(g) + Cl₂(g) → CH₃Cl(s) + HCl(g). The major factor that influences the rate of the reaction above is
Chlorination of methane requires UV light to initiate the reaction.
The energy required to initiate a chemical reaction is called
Activation energy is the minimum energy needed to start a reaction.
A decrease in the concentration of reactants in a chemical reaction will generally lead to
Lower concentration reduces collision frequency, slowing the reaction.
MnO₄⁻(aq) + Y + 5Fe²⁺(aq) → Mn²⁺(aq) + 5Fe³⁺(aq) + 4H₂O(l). In the equation above, Y is
Balancing H and charge: 8H⁺ is required to form 4H₂O and balance the equation.
Given that M is the mass of a substance deposited during electrolysis and Q is the quantity of electricity consumed, then Faraday's first law can be written as
Faraday's first law: M ∝ Q, so M = ZQ, where Z is the electrochemical equivalent.
The impurities formed during the laboratory preparation of chlorine gas are removed by
Concentrated H₂SO₄ removes moisture and impurities during chlorine preparation.
The effect of the presence of impurities such as carbon and sulphur on iron is that they
Carbon and sulphur impurities lower iron’s melting point.
A few drops of concentrated HNO₃ is added to an unknown solution and boiled for a while. If this produces a brown solution, the cation present is likely to be
Fe²⁺ is oxidized to Fe³⁺ by HNO₃, forming a brown solution.
The property of concentrated H₂SO₄ that makes it suitable for preparing HNO₃ is its
H₂SO₄’s dehydrating property helps produce HNO₃ from nitrate salts.
The bleaching action of chlorine gas is effective due to the presence of
Cl₂ reacts with water to form HClO, which is responsible for bleaching.
In the laboratory preparation of oxygen, dried oxygen is usually collected over
Oxygen is collected over mercury due to its insolubility in it.
Bronze is preferred to copper in the making of medals because it
Bronze (Cu + Sn) is stronger than pure copper, ideal for medals.
The constituent of baking powder that makes the dough rise is
NaHCO₃ decomposes to release CO₂, causing dough to rise.
What volume of 0.5 mol dm⁻³ H₂SO₄ will exactly neutralize 20 cm³ of 0.1 mol dm⁻³ NaOH solution?
H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O. Moles of NaOH = 0.1 × 0.02 = 0.002 mol. Moles of H₂SO₄ = 0.002/2 = 0.001 mol. Volume of H₂SO₄ = 0.001/0.5 = 0.002 dm³ = 4.0 cm³.
Which of the following gases is produced when a metal reacts with dilute acid?
Metals react with dilute acids to produce hydrogen gas.
The general formula of an alkyne is
Alkynes have a triple bond, with the general formula CₙH₂ₙ₋₂.
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