Use a blue or black pen only. Pencils are not allowed.
Completely fill the bubble corresponding to your chosen answer (A, B, C, or D).
Do not use checkmarks (✓) or crosses (✗).
If you need to change an answer, erase your previous mark completely.
Ensure that only one bubble is filled for each question.
bubble Sheet
Question 1
(X, Y and Z) are three transition elements used in the medical field. (X): One of its alloys is used in surgical instruments. (Y): It is used in artificial joints. (Z): One of its isotopes is used in the diagnosis and treatment of malignant tumors.
Which of the following represents the elements (X, Y and Z)?
a) X: Chromium, Y: Cobalt, Z: Cadmium
b) X: Iron, Y: Titanium, Z: Cobalt
c) X: Cobalt, Y: Vanadium, Z: Chromium
d) X: Iron, Y: Titanium, Z: Vanadium
✓ Correct Answer: (b) X = Iron | Y = Titanium | Z = Cobalt
📚 Detailed Explanation
The correct option is b) X: Iron, Y: Titanium, Z: Cobalt.
Medical Uses of Transition Metals
X = Iron (Fe): Stainless steel (Fe + Cr + Ni) is the standard alloy for surgical instruments.
Y = Titanium (Ti): Biocompatible, lightweight, and corrosion-resistant — ideal for bone implants and artificial joints.
Z = Cobalt (Co): The radioactive isotope 60Co is used in radiotherapy for malignant tumors.
Question 2
The following table shows the electronic configuration of the cations of two elements, (X) and (Y):
X²⁺: [₁₈Ar] 3d⁴ Y²⁺: [₁₈Ar] 3d²
Which of the following is correct?
a) It is difficult to oxidize X⁶⁺ to X⁷⁺
b) It is difficult to oxidize Y²⁺ to Y⁴⁺
c) It is easy to reduce X⁶⁺ to X²⁺
d) It is easy to reduce Y⁴⁺ to Y³⁺
✓ Correct Answer: (a) It is difficult to oxidize X⁶⁺ to X⁷⁺
Y²⁺ = [Ar]3d² → Y = Titanium (Ti, Z=22); Ti = [Ar]3d²4s²
Step 2: Analysis
Chromium has only 6 valence electrons (3d⁵4s¹), so its maximum oxidation state is +6. At X⁶⁺ the configuration is [Ar]3d⁰ — a complete, stable argon core. Removing a 7th electron means breaking into the noble-gas core, which is extremely difficult. ✓
(b) ✗ Ti⁴⁺ (3d⁰) is its most stable state, so oxidizing Ti²⁺ → Ti⁴⁺ is easy.
(c) ✗ Cr⁶⁺ is reduced readily to Cr³⁺ (most stable), not Cr²⁺.
(d) ✗ Ti⁴⁺ (3d⁰) is very stable; it resists gaining an electron, so reduction to Ti³⁺ is not easy.
Question 3
(X, Y, Z) are three transition elements at the end of the first transition series.
Arranged according to atomic mass: Y < Z < X
Which of the following represents the correct order of ions of these elements according to the magnetic moment?
μ = √[n(n+2)]. Therefore the order is Co²⁺ (3.87) > Ni²⁺ (2.83) > Cu²⁺ (1.73) → Z²⁺ > Y²⁺ > X²⁺ ✓
Note: Ni²⁺ (2 unpaired) has a higher moment than Cu²⁺ (1 unpaired), so Y²⁺ > X²⁺.
Question 4
Which of the following represents the correct order of processes required to obtain a stainless steel alloy from the products of reduction furnace cleaning?
a) Concentration – Roasting – Reduction – Melting with chromium
b) Concentration – Reduction – Roasting – Melting with manganese
c) Sintering – Roasting – Addition of carbon and chromium – Reduction
d) Sintering – Roasting – Reduction – Addition of carbon and chromium
✓ Correct Answer: (d) Sintering → Roasting → Reduction → Addition of C and Cr
📚 Detailed Explanation
The correct option is d).
Process Flow for Stainless Steel
1. Sintering: Fine ore dust fused into lumps suitable for blast furnace.
2. Roasting: Remove sulfur impurities; convert ore to Fe₂O₃.
3. Reduction: Fe₂O₃ + CO → Fe metal in blast furnace.
Step 4 (Filtration): Final solution contains only the copper cation. ✓
Why not (a)? Adding H₂S precipitates CuS↓ — that would REMOVE copper from the solution, leaving Ca²⁺ behind, which is the opposite of what is required.
Question 8
When adding hot, concentrated sulphuric acid to salt (X), fumes are released that turn a paper wet with starch blue.
When barium chloride solution is added to salt solution (Y), a white precipitate is formed that dissolves in dilute HCl.
Which of the following represents the product of adding silver nitrate solution to solutions of both (X and Y)?
a) X: Yellow ppt dissolves in NH₃ | Y: Yellow ppt does NOT dissolve in NH₃
b) X: Yellow ppt does NOT dissolve in NH₃ | Y: Yellow ppt dissolves in NH₃
c) X: Yellowish-white ppt | Y: Yellow ppt does NOT dissolve in NH₃
d) X: White ppt dissolves in NH₃ | Y: Yellow ppt dissolves in NH₃
✓ Correct Answer: (b) X: yellow ppt NOT dissolving in NH₃ | Y: yellow ppt dissolving in NH₃
📚 Detailed Explanation
The correct option is b).
Salt X (an iodide): Hot conc. H₂SO₄ oxidises I⁻ to violet I₂ vapour, which turns starch paper blue-black. With AgNO₃: I⁻ → AgI↓ (yellow), which is insoluble in ammonia. ✓
Salt Y (a carbonate): BaCl₂ gives BaCO₃ (white, dissolves in dilute HCl with effervescence). With AgNO₃: CO₃²⁻ → Ag₂CO₃↓ (pale yellow), which dissolves in ammonia. ✓
Key clue: starch turning blue = iodine ⇒ X is an iodide (AgI yellow, NOT a chloride).
Question 9
When 0.2 mol of the anhydrous salt XCl₂ combines with 7.2 g of water, a hydrated salt is formed with the chemical formula XCl₂·nH₂O (H=1, O=16).
Which of the following represents the value of (n)?
a) 2
b) 4
c) 6
d) 8
✓ Correct Answer: (a) n = 2
📚 Detailed Explanation
The correct option is a) n = 2.
Moles H₂O = 7.2 ÷ 18 = 0.4 mol
n = 0.4 ÷ 0.2 = 2
Question 10
When titrating an alkaline solution of concentration (M = 1 mol/L) with an acid of concentration (0.5 M), upon reaching the equivalence point, it was found that the volume of acid consumed equals the volume of the alkaline solution.
Which of the following represents the acid and the alkaline solution?
a) Hydrochloric acid and calcium hydroxide
b) Sulphuric acid and potassium hydroxide
c) Hydrochloric acid and potassium hydroxide
d) Sulphuric acid and calcium hydroxide
✓ Correct Answer: (b) Sulphuric acid and potassium hydroxide
📚 Detailed Explanation
The correct option is b).
(basicity × C × V)acid = (acidity × C × V)base
H₂SO₄ (basicity 2, 0.5 M): 2 × 0.5 × V = 1 × V
KOH (acidity 1, 1 M): 1 × 1 × V = 1 × V
⇒ equal volumes ✓
The diprotic acid at 0.5 M supplies 1 eq/L of H⁺; the monoacidic base KOH at 1 M supplies 1 eq/L of OH⁻ — so equal volumes neutralise exactly. ✓
Question 11
When equal masses of zinc react with an excess of hydrochloric acid, which of the following represents the reaction that produces the greatest volume of hydrogen gas in the shortest time?
a) A zinc strip with 0.1 M acid at 25°C
b) Zinc powder with 1 M acid at 50°C
c) Zinc powder with 0.1 M acid at 25°C
d) A piece of zinc with 1 M acid at 50°C
✓ Correct Answer: (b) Zinc powder with 1 M acid at 50°C
Which of the following diagrams represents the relationship between the concentrations of products and reactants when a piece of magnesium metal is placed in a dilute sulfuric acid solution?
Mg is in excess; H₂SO₄ is limiting. Acid concentration drops to zero; product increases and levels off. The two curves cross — diagram (c) shows this correctly.
Question 14
When a solution of a weak monoprotic acid is diluted by adding water, doubling its volume:
Which of the following happens to the value of α and the pH?
a) α decreases → becomes (1/1.414 α), and pH decreases
b) α increases → becomes (1.414 α), and pH increases
c) α doubles, and pH increases
d) α is halved, and pH decreases
✓ Correct Answer: (b) α increases to 1.414α and pH increases
📚 Detailed Explanation
The correct option is b).
α = √(Ka/C)
After doubling volume: C → C/2
α_new = √(2·Ka/C) = √2 · α = 1.414 α
[H⁺] decreases as dilution increases, so pH increases. ✓
Question 15
If the Ksp of AgCl = 1.6 × 10⁻¹⁰, then the mass of AgCl dissolved in 50 mL of water is: (AgCl = 143.5 g/mol)
a) 1.6 × 10⁻¹⁰ g
b) 0.905 × 10⁻⁴ g
c) 1.26 × 10⁻⁵ g
d) 1.81 × 10⁻⁴ g
✓ Correct Answer: (b) 0.905 × 10⁻⁴ g
📚 Detailed Explanation
The correct option is b).
s = √(1.6×10⁻¹⁰) = 1.265×10⁻⁵ mol/L
moles in 50 mL = 1.265×10⁻⁵ × 0.050 = 6.325×10⁻⁷ mol
mass = 6.325×10⁻⁷ × 143.5 ≈ 0.905×10⁻⁴ g
Question 16
In the following equilibrium reaction: 2NO + O₂ ⇌ 2NO₂
Which of the following describes what happens in this case?
a) NO and O₂ react in equal mass proportions.
b) The rate of formation of NO₂ is twice the rate of consumption of O₂.
c) The rate of consumption of O₂ equals the rate of formation of NO₂.
d) At equilibrium, the volumes of reactants and products are equal.
✓ Correct Answer: (b) Rate of formation of NO₂ = twice rate of consumption of O₂
📚 Detailed Explanation
The correct option is b).
Stoichiometry: 2 mol NO : 1 mol O₂ : 2 mol NO₂. Therefore the rate of formation of NO₂ = 2 × rate of consumption of O₂. ✓
(a) ✗ Mass ratio NO:O₂ = 60:32, not equal.
(c) ✗ Ratio O₂:NO₂ = 1:2.
(d) ✗ Volumes at equilibrium are not necessarily equal.
Question 17
A galvanic cell with electrode X in X²⁺ solution and electrode Y in Y³⁺ solution (X is anode).
Which of the following represents the total reaction of the cell?
The anode is the site of oxidation. The reaction 4OH⁻ → O₂ + 2H₂O + 4e⁻ is an oxidation (loss of electrons) and is non-spontaneous in an electrolytic cell. ✓
(a), (d) ✗ Reductions occurring at the cathode.
(b) ✗ Copper plating is reduction at the cathode.
Question 19
A galvanic cell (X) consists of two electrodes (A, B), and electrons flow from B to A through the external wire.
An electrochemical cell (Y) consisting of the same electrodes undergoes the reaction: A(s) + B²⁺(aq) → A²⁺(aq) + B(s)
Which of the following options describes cell (Y)?
a) Galvanic with positive emf; electrode (A) is negative and acts as anode
b) Galvanic with positive emf; electrode (B) is positive and acts as cathode
c) Electrolytic with negative emf; electrode (A) is negative and acts as anode
d) Electrolytic with negative emf; electrode (B) is negative and acts as cathode
✓ Correct Answer: (d) Electrolytic, negative emf, B is negative cathode
📚 Detailed Explanation
The correct option is d).
In cell X (galvanic): electrons flow B → A, so B is the anode (more active) and the spontaneous reaction is: B + A²⁺ → B²⁺ + A.
In cell Y: the given reaction A + B²⁺ → A²⁺ + B is the exact reverse → it is non-spontaneous ⇒ an electrolytic cell with a negative emf.
A is oxidised → A is the anode (positive) in an electrolytic cell.
B²⁺ is reduced at B → B is the cathode, which in an electrolytic cell is the negative electrode. ✓
(c) is wrong: in an electrolytic cell the anode is the positive electrode, not negative.
Question 20
A water tank is connected to a pipe and tap made of three metals (X, Y, Z): X = −0.40 V | Y = +0.30 V | Z = −2.71 V
The pipe acts as a sacrificial electrode for both the tank and the tap.
The tap provides cathodic protection for the tank under normal conditions.
Which represents the metals for each component?
a) Tank: Y, Tap: X, Pipe: Z
b) Tank: X, Tap: Y, Pipe: Z
c) Tank: X, Tap: Z, Pipe: Y
d) Tank: Z, Tap: Y, Pipe: X
✓ Correct Answer: (b) Tank=X, Tap=Y, Pipe=Z
📚 Detailed Explanation
The correct option is b).
Pipe = Z (−2.71 V): Most active → sacrificial anode for both tank and tap.
Tap = Y (+0.30 V): Most noble → provides cathodic protection to the tank.
Tank = X (−0.40 V): Protected cathodically by both. ✓
Question 21
A copper rod containing iron and silver impurities was purified using electrolysis.
Which of the following represents the change in electrode masses after passage of electric current?
a) Decrease in anode mass = increase in cathode mass
b) Decrease in anode mass < increase in cathode mass
c) Decrease in anode mass > increase in cathode mass
d) Decrease in anode mass = mass of undissolved impurities
✓ Correct Answer: (c) Decrease in anode mass > increase in cathode mass
📚 Detailed Explanation
The correct option is c).
At the impure anode, Cu, Fe, and Ag all dissolve → large mass decrease. At the pure cathode, only Cu²⁺ deposits → smaller mass gain (Ag falls as anode sludge, Fe²⁺ stays in solution). Therefore decrease in anode mass > increase in cathode mass. ✓
Question 22
Which of the following is correct for both a fuel cell and a mercury cell?
a) Both convert stored chemical energy into electrical energy.
b) Reduction occurs at the negative electrode in both.
c) The components of both cells are consumed during operation.
d) Both are alkaline cells and the electrolyte concentration does not change during operation.
✓ Correct Answer: (d) Both alkaline; electrolyte concentration unchanged
📚 Detailed Explanation
The correct option is d).
Both the fuel cell and the mercury cell use an alkaline (KOH) electrolyte whose concentration does not change during operation. ✓
(a) ✗ Fuel cells use externally supplied energy, not stored chemical energy.
(b) ✗ Reduction occurs at the positive electrode (cathode).
Question 23
(X, Y) are two salts of organic acids: X: (HCOO)₂CaY: (COO)₂Ca
Which of the following expresses the number of moles of organic acid and base required to prepare one mole of each salt?
Which of the following represents a compound that does NOT decolorise bromine dissolved in carbon tetrachloride?
a) The product of dropping water on calcium carbide
b) The product of the catalytic reforming of hexane
c) The product of adding concentrated H₂SO₄ to propanol at 180°C
d) The product of strong heating then rapid cooling of the dry distillation product of sodium acetate
✓ Correct Answer: (b) The product of catalytic reforming of hexane
📚 Detailed Explanation
The correct option is b).
Decolourising Br₂/CCl₄ requires an addition reaction (C=C or C≡C). The compound that does NOT is aromatic benzene.
(b) ✓ Catalytic reforming of hexane (C₆H₁₄ → C₆H₆) gives benzene. Without an FeBr₃ catalyst benzene undergoes substitution, not addition → does NOT decolourise Br₂/CCl₄.
The longest carbon chain that contains the double bond is only 5 carbons (pent-2-ene), since the C₃H₇ group is actually an isopropyl branch arrangement:
Double bond at C2 → 2-pentene
Phenyl group at C2
Methyl groups at C3 and C4
Name → 3,4-dimethyl-2-phenyl-2-pentene (option c). The "hexene" reading in (d) is wrong because the longest chain through the C=C is 5 carbons, not 6. ✓
Question 26
Upon hydrolysis in acidic medium of propyl benzoate, an acidic compound (X) is produced. When (X) reacts with the simplest aliphatic alcohol, compound (Y) is produced.
Which of the following is the isomer of compound (Y)?
a) Phenyl formate
b) Butyl formate
c) Phenyl acetate
d) Phenyl benzoate
✓ Correct Answer: (c) Phenyl acetate
📚 Detailed Explanation
The correct option is c).
X = Benzoic acid (C₆H₅COOH). With methanol → Y = Methyl benzoate (C₆H₅COOCH₃), formula C₈H₈O₂. Phenyl acetate (CH₃COOC₆H₅) has the same formula C₈H₈O₂, so it is an isomer. ✓
Question 27
From the following diagram:
Which of the following represents the number of isomers for each formula of (X, Y, Z)?
Y (C₃H₇Cl) → 2 isomers: hydrogenation removes the C=C giving a saturated chloropropane → 1-chloropropane and 2-chloropropane only (degree of unsaturation = 0, so no ring possible).
Z (C₃H₈O) → 2 isomers: alkaline hydrolysis gives the alcohols 1-propanol and 2-propanol.
Correction note: "cyclopropyl chloride" has formula C₃H₅Cl (not C₃H₇Cl), so it is NOT an isomer of Y — hence Y = 2, not 3.
Question 28
(X): A primary alcohol with one alcoholic isomer. (Y): A hydrocarbon produced by dehydration of (X). (Z): An isomer of (Y).
Which of the following represents the properties of compound (Z)?
a) More stable than normal propane
b) Burns faster than cyclic butane
c) Burns slower than normal hexane
d) Less reactive than cyclic pentane
✓ Correct Answer: (b) Burns faster than cyclic butane
📚 Detailed Explanation
The correct option is b).
X = 1-propanol → Y = Propene (C₃H₆) → Z = Cyclopropane (isomer of propene). Cyclopropane (MW=42) burns faster than cyclobutane (MW=56). ✓
Question 29
Two organic compounds (X, Y): X: C₂H₆O₂ Y: C₂H₄O₂
Which of the following is correct?
a) Both react with sodium hydroxide
b) Both react with halogenated acids
c) Both are oxidised by potassium permanganate solution
d) When they react together, an ester is formed
✓ Correct Answer: (d) When they react together, an ester is formed
📚 Detailed Explanation
The correct option is d).
X = C₂H₆O₂ = Ethylene glycol (HOCH₂CH₂OH) — a di-alcohol.
Y = C₂H₄O₂ = Acetic acid (CH₃COOH) — a carboxylic acid.
Hydrogen at 800 °C carries out the complete reduction of Fe₂O₃ to metallic iron (Fe); strong heating of iron in air then forms the magnetic oxide Fe₃O₄. ✓
Question 35
12 g of a mixture of KCl and K₂CO₃ were dissolved in water. Excess MgSO₄ solution was added, forming a precipitate of mass 5 g.
What is the percentage of KCl in the mixture? (K=39, C=12, O=16, Mg=24)
a) 35.44%
b) 68.45%
c) 31.55%
d) 40.91%
✓ Correct Answer: (c) 31.55%
📚 Detailed Explanation
The correct option is c).
Only K₂CO₃ reacts: K₂CO₃ + MgSO₄ → MgCO₃↓ + K₂SO₄ (KCl gives no precipitate).
mol MgCO₃ = 5 ÷ 84 = 0.0595 mol = mol K₂CO₃
mass K₂CO₃ = 0.0595 × 138 = 8.21 g
mass KCl = 12 − 8.21 = 3.79 g
% KCl = (3.79 / 12) × 100 ≈ 31.55%
Correction note: 0.0595 × 138 = 8.21 g (not 3.81 g) — this gives % KCl = 31.55%.
Question 36
2NO(g) + 2H₂(g) ⇌ N₂(g) + 2H₂O(v)
0.1 mol NO + 0.05 mol H₂ in 1 L container. At equilibrium: n(NO) = 0.062 mol.
What is the value of Kc?
The energy diagram for a reversible reaction shows that the activation energy of the forward reaction is smaller than that of the reverse reaction → forward reaction is exothermic.
Which graph represents the relationship between Kc and temperature?
a) Kc decreases as T increases
b) Kc increases then decreases (bell curve)
c) Kc increases as T increases
d) Kc is constant then increases
✓ Correct Answer: (a) Kc decreases as T increases
📚 Detailed Explanation
The correct option is a).
When the activation energy of the forward reaction is smaller than that of the reverse reaction, the products lie at lower energy than the reactants → the forward reaction is exothermic (ΔH < 0).
For an exothermic forward reaction, increasing the temperature shifts the equilibrium backward (toward reactants), so the amount of products falls → Kc decreases as temperature increases. ✓
Question 38
A metal is connected to the cathode of an electrolytic cell for chromium plating using Cr₂O₇²⁻ acidic electrolyte (O₂ released at anode).
How many moles of gas are released when the plated mass increases by 151 g? [Cr=52]
Z = Toluene (formed from reduction of X and dry distillation of Y). X = para-cresol (para methyl phenol), Y = sodium p-methylbenzoate. Z + H₂ → W = methylcyclohexane. ✓
Question 41
From the following diagram:
When excess KOH is added to both Y and X, which represents the compound produced?
a) In case of X: secondary alcohol, used in thermometers.
b) In case of Y: secondary alcohol, used as mouth steriliser.
c) In case of X: primary alcohol, monomer of PEG.
d) In case of Y: primary alcohol, used in pen inks.
✓ Correct Answer: (c) X → primary alcohol, monomer of PEG
📚 Detailed Explanation
The correct option is c).
X = BrCH₂CH₂Br → + 2KOH → HOCH₂CH₂OH (ethylene glycol)
X gives ethylene glycol — a primary alcohol and the monomer of PEG. ✓
Question 42
From the following diagram:
Which of the following is correct?
The following diagram represents some reactions in organic compounds:
1- State the IUPAC name of the isomer of the compound from adding excess HBr to compound (Z). 2- State the IUPAC name of the product from the reduction of compound (X). 3- Write the structural formulas for compounds (Y) and (L).
✓ Model Answer Below
📚 Detailed Explanation
Identifying the Compounds
Z = CH≡CH (acetylene) → L = CH₃CHO (ethanal)
X = CH₃COOH (acetic acid), Y = CH₃COONa
Answers
1. Excess HBr to Z (CH≡CH) → CH₃CHBr₂ (1,1-dibromoethane). Its isomer = 1,2-dibromoethane.
2. Reduction of X (CH₃COOH) → Ethanol.
3. Y (Sodium acetate): CH₃COONa | L (Ethanal): CH₃CHO
Model answer guiding nine
📋 Answer Key - Bubble Sheet
✓ Model Answers for All Questions
44 Multiple Choice + 2 Essay Questions
Questions 1-23
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Questions 24-46
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ESSAY QUESTION
Q46
ESSAY QUESTION
Total Score: ((1:32)x1M =32M +(33:42)x2M =24M MCQ ) = 56M + 2 Essay x2M = 4M total 56+4=60M
Filled circle = Correct Answer | Empty circle = Incorrect Option
