▶️ Answer/Explanation
According to the kinetic particle theory, temperature is a direct measure of the average kinetic energy of gas molecules. Elevating the temperature causes particles to absorb thermal energy and convert it into mechanical motion, forcing them to travel at their fastest velocities. Conversely, gas particle separation is heavily dictated by external pressure: a high pressure compresses gas into a smaller volume, packing particles tightly together, whereas a low pressure minimizes constraints, allowing the rapidly moving molecules to expand into the available space and stay furthest apart. Therefore, the perfect pairing to maximize both speed and distance is high temperature and low pressure, rendering row C correct.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
The kinetic particle theory defines the macroscopic properties of a liquid through its microscopic particle dynamics. In a liquid state, the attractive intermolecular forces are strong enough to keep the particles close together and touching (maintaining a fixed volume), yet weak enough to prevent them from staying in a rigid structural position. This configuration allows particles to continuously change positions by sliding past or over one another, enabling the fluid to flow and adapt to the shape of its container, validating option C. Statements A and B are macroscopically incorrect descriptions of volume and shape dynamics, while option D uniquely defines a gaseous state.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
To determine the physical state of a compound at any temperature, its current condition is compared directly to its fixed transition parameters: below the melting point ($< 71^\circ\text{C}$), it remains a solid; between the melting and boiling points ($71^\circ\text{C}$ to $375^\circ\text{C}$), it exists as a liquid; and above the boiling point ($> 375^\circ\text{C}$), it converts into a gas. Evaluating option D, $80^\circ\text{C}$ lies firmly within the liquid range ($71^\circ\text{C} < 80^\circ\text{C} < 375^\circ\text{C}$) and $400^\circ\text{C}$ sits completely above the vaporization threshold ($400^\circ\text{C} > 375^\circ\text{C}$), satisfying both conditions perfectly. The other choices present incorrect physical states for the specified thermal values, establishing row D as the only entirely correct statement.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
By syllabus definition, the term “nucleon” refers collectively to any subatomic particle located securely inside the dense central core, or nucleus, of an atom. Since the atomic nucleus is composed strictly of protons and neutrons (while electrons occupy the vast outer shells or energy levels), the nucleon number—also widely referred to as the mass number—is calculated as the sum of these two specific heavy particles inside the core, validating choice C. Protons alone define the atomic/proton number (B), while electrons are excluded from mass calculations due to their negligible relative mass, ruling out option D.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
For a neutral atom, the number of protons equals its total number of electrons. Given that the atom has three electron shells, its inner shells must be entirely filled under standard electronic configuration rules, yielding a structure of $2, 8, 3$. Summing these values ($2 + 8 + 3 = 13$) determines a proton number of 13, identifying the element as Aluminium ($\text{Al}$) in Period 3, Group III. A proton count of 13 rules out options C and D. Between rows A and B, a value of 27 represents the total mass/nucleon number of a standard Aluminium nucleus ($\text{Mass} = \text{Protons} + \text{Neutrons}$), rather than the standalone neutron count. Subtracting the proton count from the mass number ($27 – 13 = 14$) yields exactly 14 neutrons, identifying row A as correct.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
Covalent bonding involves the sharing of pairs of valence electrons between non-metal atoms to achieve stable, full outer shells resembling noble gas configurations. In a molecule of ammonia ($\text{NH}_3$), the central nitrogen atom has 5 outer-shell electrons and shares 1 electron with each of the three hydrogen atoms, creating exactly 3 single covalent bonds (leaving 1 unshared lone pair). In a molecule of hydrogen chloride ($\text{HCl}$), the chlorine atom has 7 valence electrons and shares a single pair of electrons with a single hydrogen atom, resulting in exactly 1 single covalent bond. This establishes that row A correctly identifies the number of shared bonding pairs for both chemical species.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
To determine the correct descriptions, let’s look at the specific macromolecular features of diamond. Diamond is an allotrope of carbon characterized by a rigid, three-dimensional giant covalent lattice structure (Statement 4 is correct). Within this network, each individual carbon atom uses all four of its valence electrons to form strong covalent bonds with four other neighboring carbon atoms in a uniform tetrahedral shape (Statement 1 is incorrect; Statement 2 is correct). Because the atoms are interlocked in a continuous 3D matrix rather than separate parallel planes, diamond does not contain layers that slide over one another—a property unique to graphite (Statement 3 is incorrect). Since only statements 2 and 4 are scientifically accurate, option C is the correct choice.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
To compute the reacting mass, we first evaluate the moles of reacting Magnesium using its relative atomic mass ($A_r(\text{Mg}) = 24$). Dividing the given mass by its atomic mass ($\text{moles} = 48\text{ g} / 24\text{ g/mol}$) yields exactly $2\text{ moles}$ of $\text{Mg}$. According to the balanced stoichiometric equation, the molar ratio between $\text{Mg}$ and $\text{MgO}$ is a direct $2:2$ (or $1:1$) relationship, meaning $2\text{ moles}$ of $\text{Mg}$ will yield exactly $2\text{ moles}$ of $\text{MgO}$. The relative formula mass of magnesium oxide is calculated as $M_r(\text{MgO}) = 24 + 16 = 40$. Multiplying the number of moles by this formula mass ($\text{mass} = 2\text{ moles} \times 40\text{ g/mol}$) results in $80\text{ g}$ of $\text{MgO}$, making option C the correct answer.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
When hydrocarbons burn in a “limited amount of oxygen,” incomplete combustion takes place. Unlike complete combustion which yields non-toxic carbon dioxide ($\text{CO}_2$), incomplete combustion produces toxic carbon monoxide ($\text{CO}$) gas along with water vapor ($\text{H}_2\text{O}$). This chemical rule immediately eliminates option A (which shows complete combustion) and option C (which incorrectly yields elemental $\text{H}_2$). To choose between B and D, we must check for correct stoichiometric balancing. In option B, the right side has $3 \times 1 = 3$ oxygen atoms from $\text{CO}$ and $4 \times 1 = 4$ from $\text{H}_2\text{O}$, totaling 7 oxygen atoms, which cannot be formed from an even number of atoms in $4\text{O}_2$ (8 oxygen atoms). Option D is perfectly balanced on both sides with 6 carbon atoms, 16 hydrogen atoms, and 14 oxygen atoms ($2\text{C}_3\text{H}_8 + 7\text{O}_2 \rightarrow 6\text{CO} + 8\text{H}_2\text{O}$), making it the correct equation.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
By international convention and syllabus definition, the relative atomic mass ($A_r$) of any element is calibrated against a single, universally accepted baseline. The standard reference framework is an atom of the Carbon-12 isotope (${}^{12}\text{C}$), which is assigned an absolute mass of exactly 12 arbitrary mass units. Consequently, one atomic mass unit is defined precisely as $\frac{1}{12}\text{th}$ the mass of a single Carbon-12 atom, and all other atomic masses on the Periodic Table are calculated relative to this standard, establishing option D as the correct answer.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
By literal syllabus definition, electrolysis means the breaking down (“-lysis”) of a substance using electricity (“electro-“). For this process to take place, the target substance must be an ionic compound containing free-moving ions, which is achieved only when it is in a molten state or dissolved in an aqueous solution. Passing a direct electric current through this medium forces the migration of ions to oppositely charged electrodes, where redox reactions decompose the compound into its constituent elements, making row B the exact definition. Option A describes simple ionization, row C defines the “electrolyte” itself, and row D describes “electroplating,” which is a specific application rather than the core definition.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
In electroplating, the object to be coated (the copper spoon) must be placed at the cathode, which is the negative electrode, so that positively charged metal ions migrate to it and get reduced. To coat the spoon with silver, the electrolyte must contain silver ions (such as aqueous silver nitrate), and a silver anode is used to replenish those ions in solution. At the negative electrode, silver ions gain electrons to form solid silver metal on the spoon, making option D correct. Options A, B, and C are incorrect because the anode should be pure silver, the spoon must be the cathode, and a silver-containing solution must serve as the electrolyte.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
In an exothermic reaction, thermal energy is transferred from the chemical system to the surroundings, meaning the total potential energy of the products is lower than that of the reactants. Consequently, a reaction pathway diagram shows the line for reactants drawn higher than the line for products. Since energy is net-released during this process, the correct row pairing these properties is row B. Options C and D are incorrect because they describe a profile where reactants are lower than products, which represents an endothermic process.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
In an endothermic reaction, thermal energy is absorbed from the surroundings, causing the temperature of the surroundings to decrease — so the final temperature will be lower than the initial temperature. Examining the data: Reaction 1 shows a temperature rise (19°C → 28°C), making it exothermic; Reaction 3 shows no temperature change (20°C → 20°C), indicating neither type under these conditions; and Reaction 4 shows a slight temperature increase (18°C → 19°C), also classifying it as exothermic. Only Reaction 2 shows a temperature decrease (18°C → 16°C), confirming that it alone absorbs heat from the surroundings and is therefore endothermic.
✅ Answer: (C)
✅ Answer: (C)
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▶️ Answer/Explanation
A chemical change produces one or more new substances with different chemical properties, and the process is generally irreversible. Cooking an egg causes the proteins within it to permanently denature and change structure, forming new substances — a clear sign of a chemical change. In contrast, boiling water and melting ice are physical changes because only the state of matter changes while the chemical identity of water (H₂O) remains the same. Dissolving sugar is equally a physical change, since the sugar molecules remain chemically intact and can be fully recovered by evaporating the water.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Experiment 2 produces 100 cm³ of hydrogen in only 100 s compared to 250 s in Experiment 1, meaning the rate of reaction has increased. Adding a catalyst (1) lowers the activation energy and speeds up the reaction; using zinc powder (3) greatly increases the surface area exposed to the acid, raising the frequency of effective collisions; and heating the acid (4) gives particles more kinetic energy, increasing both the frequency and energy of collisions. Diluting the acid (2), however, reduces the concentration of H⁺ ions, which decreases the collision frequency and therefore slows the reaction — so condition 2 cannot be responsible for the faster result seen in Experiment 2.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
Blue copper(II) sulfate is correctly described as hydrated (CuSO₄·5H₂O) because it contains water molecules chemically combined within its crystal structure — it is not merely a mixture of copper sulfate and water. When heated, it loses this water of crystallisation to form white anhydrous copper(II) sulfate (CuSO₄). The fact that adding water back to the white solid restores the blue colour and releases heat confirms that the reaction is reversible — the forward reaction (dehydration by heating) can be undone by the reverse reaction (rehydration by adding water). Both options A and B are incorrect because copper(II) sulfate is a pure compound, not a mixture, and option D is eliminated because the reaction clearly can be reversed.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
Statement 1 is correct: oxidation is defined at Core level as the gain of oxygen by a substance during a reaction. Statement 2 is also correct: the defining feature of a redox reaction is that oxidation and reduction always occur simultaneously — one substance gains oxygen while another loses it, so neither process can happen independently. Statement 3 is incorrect: reduction is the loss of oxygen (not the gain), which is the exact opposite of what is stated. Since only statements 1 and 2 are accurate descriptions of redox reactions, option A is the correct choice.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
Sodium oxide (Na₂O) is a basic oxide because it is the oxide of a metal (sodium) and reacts with acids to form a salt and water. Sulfur dioxide (SO₂), on the other hand, is an acidic oxide — it is formed by a non-metal and dissolves in water to produce sulfurous acid — so options C and D are immediately eliminated. An alkali is precisely defined as a soluble base, meaning a base that dissolves in water to produce hydroxide ions (OH⁻) in solution. Option A incorrectly describes an alkali as an insoluble base, which would instead describe an ordinary base that cannot form an alkaline solution. Therefore, sodium oxide as the basic oxide paired with the correct definition of an alkali as a soluble base makes option B the only correct row.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Aqueous ammonia is a weak alkali with a pH of approximately 11, so any indicator that responds to alkaline conditions will give a blue colour in it. Litmus turns blue in any alkaline solution (pH above 7), confirming statement 1. Thymolphthalein is colourless in acidic and neutral solutions but turns blue in alkaline solutions above pH 9.3 — aqueous ammonia comfortably exceeds this threshold, confirming statement 2. Universal indicator produces a blue to violet colour in alkaline solutions, with the exact shade depending on the pH, so it too turns blue in aqueous ammonia, confirming statement 3. Since all three indicators show a blue colour in the presence of aqueous ammonia, all three statements are correct.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
The question specifies that an alkaline gas is produced, which immediately identifies gas Y as ammonia (NH₃) — the only common alkaline gas — eliminating options B and D where chlorine is suggested, since chlorine is an acidic gas, not alkaline. To release ammonia from an ammonium salt, the salt must be heated with a base such as sodium hydroxide, following the reaction: NH₄Cl + NaOH → NaCl + H₂O + NH₃. Hydrochloric acid (options A and B) is an acid and would simply react with ammonium chloride to form a salt solution rather than releasing any gas. Therefore, solution X must be sodium hydroxide and gas Y must be ammonia.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
When two aqueous solutions are mixed, an insoluble salt (precipitate) forms only if the ions from the two solutions combine to give a product that is insoluble. Mixing lead(II) nitrate and potassium carbonate produces lead(II) carbonate and potassium nitrate: the table confirms that lead(II) carbonate is insoluble, so it immediately precipitates out of solution, while potassium nitrate remains dissolved. For the other options: A produces barium nitrate (soluble) and zinc chloride (soluble); B involves two nitrate solutions whose ions cannot combine to form any new salt; and D produces potassium nitrate (soluble) and zinc sulfate (soluble) — none of these yield a precipitate. Only option C results in the formation of an insoluble salt.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
Going down Group VII, melting points increase consistently: chlorine (−101°C) → bromine (−7°C) → iodine (114°C). Since astatine is below iodine in the group, this trend predicts its melting point must be higher than iodine’s 114°C, which is already higher than both bromine and chlorine — making option D correct. The trend in physical states also shows that as melting points rise, halogens progress from gas to liquid to solid; astatine must therefore be a solid at room temperature, eliminating options A and B. Option C is clearly wrong because it incorrectly places astatine’s melting point below chlorine’s, which contradicts the downward trend entirely.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
Each clue can be matched to one element by applying knowledge of physical properties and periodic trends. For J (highest density): copper has a density of approximately 8.96 g/cm³, far greater than bromine (~3.12 g/cm³) and lithium (~0.53 g/cm³), so J = copper. For L (highest reactivity with water): lithium is a Group I alkali metal that reacts readily with cold water to produce hydrogen gas, whereas copper does not react with water at all and bromine is a non-metal halogen — so L = lithium. For M (highest atomic number): bromine has atomic number 35, compared to copper (29) and lithium (3), so M = bromine. This matches option A perfectly.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
Going down Group I, three key trends apply: melting point decreases, density increases, and reactivity increases. Option B is correct because melting point decreases down the group, meaning lithium (at the top) has a higher melting point than potassium (further down) — lithium melts at approximately 180°C while potassium melts at approximately 63°C. Option A is incorrect because density increases down the group, so caesium has a greater density than rubidium, not the other way round. Option C is incorrect because reactivity increases down the group, making rubidium more reactive than potassium. Option D is incorrect because all Group I elements have exactly one outer shell electron — this is the defining feature of the group and does not change going down it.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Noble gases are monatomic — each particle consists of a single atom that exists entirely on its own, never bonded to any other atom. A mixture of noble gases must therefore be represented by individual, unbonded atoms of more than one size (representing different noble gas elements such as helium, neon, and argon) moving freely and independently. Diagram A shows exactly this: separate single atoms of two or more different sizes with no bonds between them, confirming it is a mixture of monatomic noble gas particles. Diagrams showing paired or grouped atoms would suggest diatomic molecules or compounds, which noble gases do not form due to their full outer electron shells and consequent chemical unreactivity.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
Brass is an alloy of copper and zinc — not copper and nickel — so statement 3 is factually incorrect and eliminates options C and D. Statement 2 is also wrong: brass, like all metals and metallic alloys, contains delocalised electrons that allow it to conduct electricity freely. Statements 1 and 4 are both correct: when zinc atoms (of a different size to copper atoms) are introduced into the copper lattice, they distort the regular layered structure, preventing the layers from sliding easily over one another — this makes brass both harder and stronger than pure copper. Since only statements 1 and 4 are correct, option B is the right answer.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Aircraft bodies must be made from a material that is both lightweight and structurally strong — minimising the aircraft’s total mass is essential for fuel efficiency and the ability to achieve flight, while sufficient strength is needed to withstand the mechanical stresses experienced during flight. Aluminium’s low density means aircraft bodies weigh far less than they would if made from denser metals such as steel or copper, and its notable strength (especially when alloyed) ensures the structure remains safe and intact under pressure. Although aluminium does conduct electricity and heat, these properties are not relevant to its use in aircraft bodywork and are therefore not the reason for its selection in this application.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
The observations allow a clear reactivity order to be deduced. Q reacts rapidly with both water and dilute acid, placing it at the top as the most reactive. S reacts slowly with water but rapidly with acid, indicating it is less reactive than Q but still reactive enough to displace hydrogen from both reagents. P shows no reaction with water but fizzes slowly with acid, so it is less reactive than S. R shows no reaction with either water or acid, making it the least reactive of the four — eliminating option D. The correct reactivity order is Q > S > P > R, which directly confirms that option B is correct: Q is more reactive than S. Options A and C contradict this established order entirely.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
The blast furnace involves a carefully sequenced set of reactions. The heat needed to sustain the process comes from the combustion of coke (carbon) in the hot air blast: C + O₂ → CO₂. This exothermic reaction produces carbon dioxide, making option D correct. Option A is wrong because carbon monoxide is not reduced — it is actually oxidised (it gains oxygen) as it reduces iron(III) oxide to iron, forming CO₂. Option B is incorrect because it is carbon monoxide, not carbon dioxide, that acts as the reducing agent for iron(III) oxide: Fe₂O₃ + 3CO → 2Fe + 3CO₂. Option C is wrong because slag forms when calcium oxide (produced by thermal decomposition of limestone) reacts with silicon dioxide impurities, not when calcium carbonate reacts with carbon dioxide.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
Nitrates (from fertilisers) and phosphates (from fertilisers and detergents) are both nutrients that, when present in excess in river water, stimulate the rapid and uncontrolled growth of algae on the water surface. This algal bloom blocks sunlight from reaching plants below, causing them to die; when the large mass of algae and plants subsequently decomposes, the bacteria responsible consume vast amounts of dissolved oxygen from the water, leading to deoxygenation and the death of aquatic life. Harmful microbes (statement 2) cause disease in living organisms but do not directly deplete dissolved oxygen in this way. Metal compounds (statement 3) may be toxic to aquatic organisms but are not responsible for deoxygenation through this nutrient-driven process.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Oxides of nitrogen (NOₓ), produced mainly by high-temperature combustion in car engines, are responsible for all three of the listed adverse effects. They react with volatile organic compounds in the presence of sunlight to generate photochemical smog (effect 1), a brownish haze that reduces visibility and irritates the eyes. They also directly irritate the lining of the lungs and airways, causing and worsening respiratory problems such as asthma (effect 2). Furthermore, oxides of nitrogen dissolve in atmospheric moisture to form nitric acid, which falls as acid rain (effect 3), damaging ecosystems, buildings, and statues. Since NOₓ is linked to all three effects, all three statements are correct.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
Option A is incorrect because kerosene is used as jet fuel, not as a fuel for ships — ship fuel comes from the heavier fuel oil fraction. Option B is incorrect because fractions with the highest boiling points have the longest chains and condense at the hottest part of the column, which is at the bottom, not the top. Option C is incorrect because naphtha contains smaller hydrocarbon molecules (roughly C₅–C₁₀) than the lubricating oil fraction (roughly C₂₀–C₅₀). Option D is correct: the refinery gas fraction consists of the smallest hydrocarbon molecules, including methane (CH₄), which contains exactly five atoms in total (one carbon and four hydrogen atoms), making this a valid description of molecules found in that fraction.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
NPK fertilisers must supply all three essential elements: nitrogen (N), phosphorus (P), and potassium (K). Checking each option against this requirement: option A provides N (from ammonium nitrate) and P (from calcium phosphate) but no K; option B provides N (from ammonium nitrate) and K (from potassium chloride) but no P; option D provides N and K (both from potassium nitrate) but calcium carbonate contributes neither P nor K. Only option C supplies all three elements — ammonium phosphate [(NH₄)₃PO₄] provides both N and P, while potassium chloride (KCl) supplies K — making it the only pair that satisfies the complete NPK requirement for plant growth.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
Each option can be checked by identifying the first member of the series and calculating its Mᵣ. For alkanes (A), the first member is methane (CH₄): Mᵣ = 12 + (4×1) = 16, not 12. For alkenes (B), the first member is ethene (C₂H₄): Mᵣ = (2×12) + (4×1) = 28, not 14. For alcohols (C), the first member is methanol (CH₃OH): Mᵣ = 12 + (3×1) + 16 + 1 = 32 — this matches exactly. For carboxylic acids (D), the first member is methanoic acid (HCOOH): Mᵣ = 1 + 12 + 16 + 16 + 1 = 46, not 60. Only option C gives the correct relative molecular mass for the first member of its series.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
The ability to decolourise bromine water is the standard chemical test for an unsaturated hydrocarbon. Unsaturated hydrocarbons contain at least one carbon-carbon double bond (C=C), which undergoes an addition reaction with bromine, breaking the orange-brown colour and producing a colourless dibromo compound. This immediately identifies the hydrocarbon as an alkene, eliminating options A and C since alkanes are saturated and do not react with bromine water under normal conditions. Option B (C₂H₆) is the formula for ethane, a saturated alkane. Option D is correct: alkenes follow the general formula CₙH₂ₙ, and only alkenes (unsaturated hydrocarbons) decolourise bromine water through addition reactions.
✅ Answer: (D)
✅ Answer: (D)
▶️ Answer/Explanation
The industrial manufacture of ethanol from ethene involves a hydration reaction, where steam is added across the double bond of ethene in the presence of an acid catalyst (typically phosphoric acid, H₃PO₄) at a high temperature of 300 °C and a pressure of 6000 kPa/60 atm. Option A is incorrect because 30 °C is far too low for this reaction to proceed at a useful rate. Options C and D are both wrong because fermentation uses glucose (a sugar) as the starting material — not ethene — and proceeds at 25–35 °C with yeast in the absence of oxygen. Option D is doubly incorrect as 300 °C would destroy the yeast enzymes needed for fermentation.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
When any acid reacts with a carbonate, the carbonate ion (CO₃²⁻) is decomposed by the acid’s hydrogen ions, releasing carbon dioxide gas, along with water and the corresponding salt. In this case, ethanoic acid reacts with sodium carbonate to produce sodium ethanoate (CH₃COONa), water, and carbon dioxide: 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂. Hydrogen gas would only be produced if an acid reacted with a metal, not a carbonate. Carbon monoxide and oxygen are not products of any acid–carbonate reaction under these conditions.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
The apparatus shown is a filtration setup, where the filter paper separates an insoluble solid from a liquid. Sand is insoluble in water and is therefore retained by the filter paper as the residue, while the aqueous salt solution passes through the filter paper and is collected as X — the filtrate. X cannot be described as just the solvent, because the dissolved salt is also present in the liquid that passes through; nor can it be the solute alone, as that would imply dry salt crystals rather than a solution. The term “filtrate” correctly describes the entire liquid fraction (water plus dissolved salt) that passes through the filter.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
In a titration, the solution of known concentration — here the 0.1 mol/dm³ sodium hydroxide — is the titrant and is always delivered from a burette, because a burette can dispense variable volumes with high precision (readable to ±0.05 cm³), which is essential for locating the exact end-point. A volumetric pipette is used to transfer a fixed, precise volume of the analyte (the lemon juice) into the flask, not to add the titrant. A measuring cylinder lacks the precision required for titration work, and a delivery tube is used for directing gases in gas-collection experiments, not for liquid addition in titrations.
✅ Answer: (A)
✅ Answer: (A)