Which of the following raw materials is used in the plastic industry?
Ethene (C₂H₄) is the primary monomer used in the production of polyethene (polyethylene), a major plastic material, through polymerization processes.
Which of the following organic compounds can undergo both addition and substitution reactions?
Benzene, an aromatic hydrocarbon, undergoes electrophilic substitution (e.g., nitration) due to its stable ring and addition reactions (e.g., hydrogenation to cyclohexane) under specific conditions, unlike alkanes which primarily undergo substitution.
Which of the following represents a redox reaction?
In this reaction, S in H₂S is oxidized from -2 to 0 in S, and S in SO₂ is reduced from +4 to 0 in S, making it a redox (reduction-oxidation) process; others are precipitation, neutralization, or decomposition without electron transfer.
The process of extraction of iron from its ore is
Iron ore (Fe₂O₃) is reduced to iron metal using carbon monoxide in the blast furnace: Fe₂O₃ + 3CO → 2Fe + 3CO₂, where Fe³⁺ gains electrons to form Fe.
What is the solubility of a salt if 0.4 g of it is obtained on evaporating 200 cm³ of its saturated solution to dryness?
Solubility is the mass dissolved in 1 dm³. 0.4 g in 200 cm³ (0.2 dm³) means in 1 dm³: (0.4 g / 0.2 dm³) = 2.0 g dm⁻³.
An acidic salt has
Acidic salts, like NaHSO₄, hydrolyze in water to produce H⁺ ions, making the solution acidic (pH < 7), due to the weak base-strong acid nature.
A reaction is endothermic if the
Endothermic reactions absorb heat from surroundings, cooling the vessel; ΔH > 0, and bond breaking requires more energy than forming releases.
In which of the following compounds does hydrogen form ionic compound?
NaH is sodium hydride, an ionic compound where H⁻ (hydride ion) bonds with Na⁺; others are covalent.
Consider the following reaction equation: Br₂ + 2KI → 2KBr + I₂. Bromine is reacting as
Br₂ gains electrons (oxidizes I⁻ to I₂), acting as oxidizing agent; I⁻ is reducing agent.
An organic compound has the empirical formula CH₂. If its molar mass is 42 g mol⁻¹, what is its molecular formula? [H = 1.0, C = 12.0]
Empirical mass = 14 g/mol. n = 42 / 14 = 3. Molecular = (CH₂)₃ = C₃H₆.
Ethene is produced from ethanol by
Dehydration of ethanol (C₂H₅OH) with conc. H₂SO₄ removes H₂O to form ethene (C₂H₄).
Consider the following equilibrium reaction: B₂(g) ⇌ 2AB₃(g) ΔH = +X kJ mol⁻¹ the backward reaction will be favoured by
Forward endothermic (ΔH > 0), so backward (exothermic) favored by decreasing temperature, per Le Chatelier's principle.
What is the mass of solute in 500 cm³ of 0.005 mol dm⁻³ H₂SO₄? [H = 1.0, O = 16.0, S = 32.0]
Number of moles = concentration × volume = 0.005 mol dm⁻³ × 0.5 dm³ = 0.0025 mol. Molar mass of H₂SO₄ = 2(1) + 32 + 4(16) = 98 g mol⁻¹. Mass = 0.0025 × 98 = 0.245 g.
Pure water can be made to boil at a temperature lower than 100°C by
Boiling point decreases with reduced pressure, as vapor pressure equals atmospheric pressure at lower temperature; used in vacuum distillation.
Which of the following salts has the highest solubility at 20°C?
At 20°C, solubility: NaCl ~36 g/100g water, KNO₃ ~31 g/100g, KCl ~34 g/100g, Na₂SO₄ ~19 g/100g; NaCl has the highest.
When undissolved salt is added to a saturated solution, the
A saturated solution holds maximum solute at that temperature; excess undissolved salt remains, maintaining equilibrium without change.
When substance X was added to a solution of bromine water, the solution became colourless. X is likely to be
Propene (alkene) decolorizes Br₂ water via addition reaction, forming dibromopropane; alkanes, acids, alcohols do not.
The preferential discharge of ions during electrolysis is influenced by the
Electrode nature (inert vs reactive) affects ion discharge; inert (Pt) follows standard potential, reactive may alter.
The valence electrons of ¹²Mg are in the
Mg atomic number 12, electron config 1s² 2s² 2p⁶ 3s²; valence electrons in 3s orbital.
Stainless steel is an alloy comprising of
Stainless steel is primarily iron with carbon and nickel for corrosion resistance and strength.
The number of hydrogen ions in 1.0 dm³ of 0.02 mol dm⁻³ tetraoxosulphate (VI) acid is [N_A = 6.02 × 10²³]
H₂SO₄ provides 2 H⁺, so moles H⁺ = 2 × 0.02 = 0.04 mol. Number = 0.04 × 6.02 × 10²³ = 2.408 × 10²² ≈ 2.4 × 10²².
The most suitable substance for putting out petrol fire is
Sand smothers petrol (class B) fires by cutting oxygen supply; water spreads it, CO₂ for enclosed, blanket for small.
The following factors would contribute to environmental pollution except
Photosynthesis consumes CO₂, reducing pollution; ammonia production, cement (dust), combustion (gases) pollute air.
The position of equilibrium in a reversible reaction is affected by
Changing concentration shifts equilibrium to oppose change (Le Chatelier); particle size/stirring/catalyst affect rate, not position.
Which of the following processes involves the absorption of heat during melting?
Fusion (melting) absorbs latent heat of fusion to overcome intermolecular forces without temperature change.
Which of the following statements best explains the differences between a gas and a vapour?
Vapour refers to gaseous form of a substance that can be liquefied at or near room temperature by pressure increase; gases require much lower temperatures.
Consider the following reaction equation: 2HCl + Ca(OH)₂ → CaCl₂ + 2H₂O, what is the volume of 0.1 mol dm⁻³ HCl that would completely neutralize 25 cm³ of 0.3 mol dm⁻³ Ca(OH)₂?
Moles Ca(OH)₂ = 0.3 × 0.025 = 0.0075 mol. Ratio 1:2, moles HCl = 0.015 mol. Volume HCl = 0.015 / 0.1 = 0.15 dm³ = 150 cm³.
Cu and HNO₃ are not suitable for preparing hydrogen gas because of their
Cu is below H in reactivity series, doesn't displace H₂; HNO₃ is oxidizing, oxidizes H₂ to water instead of liberating it.
Which of the following formula cannot be empirical formula?
Empirical formula shows simplest ratio; C₂ implies CH₀ or non-integer H, impossible for hydrocarbons; others possible with H.
One of the criteria for confirming the purity of benzene is to determine its
Pure substances have sharp boiling/melting points; deviation indicates impurities.
When chlorine is passed through a sample of water, the pH of the water sample would be
Cl₂ + H₂O → HCl + HOCl, producing acid (HCl), lowering pH below 7.
How many atoms are contained in 0.2 moles of nitrogen? [N_A = 6.02 × 10²³]
N₂ has 2 atoms per molecule, moles N atoms = 2 × 0.2 = 0.4 mol. Number = 0.4 × 6.02 × 10²³ = 2.408 × 10²³.
The strength of metallic bonds depends on the
More valence electrons per atom allow more delocalized electrons, stronger electrostatic attraction in the 'sea' of electrons model.
When I⁻ is added to AgNO₃ solution, crystals of AgI form on surface. This indicates that I⁻ is
Precipitation of AgI shows I⁻ dissociated from KI, reacting with Ag⁺ to form insoluble AgI; no redox, just ionic reaction.
The empirical formula of a compound containing 0.067 mol Cu and 0.066 mol O is [Cu = 63.5, O = 16.0]
Ratio Cu:O ≈ 0.067:0.066 ≈ 1:1, so CuO.
The change in the oxidation state of iron in the reaction represented by the equation below is 2FeCl₃ + H₂S → 2FeCl₂ + S + 2HCl
Fe in FeCl₃ is +3, in FeCl₂ is +2, reduced by H₂S.
Which of the following method can be used to separate blood cells from plasma?
Centrifugation separates denser blood cells (sediment) from lighter plasma (supernatant) based on density.
Which of the following statements about ionic radius is correct? Ionic radius
Higher nuclear charge pulls electrons closer, decreasing ionic radius for isoelectronic ions or in a period.
Analysis of a hydrocarbon shows that it contains 0.92 g of carbon per gram of the compound. The mole ratio of carbon to hydrogen in the compound is [H = 1.0, C = 12.0]
C = 0.92g, H = 0.08g. Moles C = 0.92/12 ≈ 0.0767, H = 0.08/1 = 0.08. Ratio ≈ 0.0767:0.08 ≈ 1:1 (CH).
The law of definite proportions states that
Proust's law: A compound always contains elements in fixed mass ratio, e.g., water always 8:1 H:O by mass, regardless of source.
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