ECAT — Engineering College Admission Test (UET)

ECAT Chemistry — Transition Elements and Industrial Chemistry (Set 4)

Take the ECAT Chemistry — Transition Elements and Industrial Chemistry (Set 4): 30 multiple-choice questions (40 minutes) with instant scoring and a full…

What this test covers

30 ECAT Chemistry

Sample questions with answers

The first 5 questions of this test, with the correct answer and explanation.

Q1. Which ion is both colourless in solution and diamagnetic?
- A. Ni²⁺
- B. Co²⁺
- C. Cu⁺ ✓
- D. Cu²⁺
Answer: C. Cu⁺
Explanation: Cu⁺ is 3d¹⁰: a full d subshell has no unpaired electrons (diamagnetic) and no d–d transitions (colourless). Cu²⁺ (d⁹), Ni²⁺ (d⁸) and Co²⁺ (d⁷) are coloured and paramagnetic.
Q2. What is the spin-only magnetic moment of the Mn³⁺ ion (Z = 25)?
- A. 2.83 BM
- B. 5.92 BM
- C. 3.87 BM
- D. 4.90 BM ✓
Answer: D. 4.90 BM
Explanation: Mn³⁺ is [Ar] 3d⁴ with 4 unpaired electrons (high spin). μ = √[n(n+2)] = √24 = 4.90 BM.
Q3. How many unpaired electrons are there in [Fe(H₂O)₆]²⁺ and in [Fe(CN)₆]⁴⁻ respectively? (H₂O is a weak-field and CN⁻ a strong-field ligand)
- A. 4 and 4
- B. 4 and 0 ✓
- C. 2 and 0
- D. 0 and 4
Answer: B. 4 and 0
Explanation: Both complexes contain Fe²⁺ (d⁶). With weak-field H₂O: t₂g⁴e_g² has 4 unpaired electrons. With strong-field CN⁻: t₂g⁶ has all paired, so 0.
Q4. 1 mol of CoCl₃·4NH₃ gives 1 mol of AgCl precipitate with excess AgNO₃. Its formula is best written as
- A. [Co(NH₃)₄Cl₂]Cl ✓
- B. [Co(NH₃)₄Cl]Cl₂
- C. [Co(NH₃)₄]Cl₃
- D. [Co(NH₃)₄Cl₃]
Answer: A. [Co(NH₃)₄Cl₂]Cl
Explanation: Only chloride outside the coordination sphere precipitates. One free Cl⁻ means two Cl⁻ are ligands: [Co(NH₃)₄Cl₂]Cl. Co has coordination number 6.
Q5. In sodium nitroprusside, Na₂[Fe(CN)₅NO], the nitrosyl ligand is NO⁺. What is the oxidation state of iron?
- A. +1
- B. 0
- C. +2 ✓
- D. +3
Answer: C. +2
Explanation: 2(+1) + x + 5(−1) + (+1) = 0 gives x = +2.

The other 25 questions

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Q6. [Pt(NH₃)₂Cl₂] exists as two geometrical isomers (cis and trans). This shows that the complex is
- A. linear
- B. tetrahedral
- C. square planar
- D. octahedral
Q7. How many stereoisomers does the octahedral complex [Co(en)₃]³⁺ have (en = ethane-1,2-diamine, a bidentate ligand)?
- A. 3
- B. 1
- C. 2, an enantiomeric pair
- D. 4
Q8. What is the effective atomic number (EAN) of iron in K₃[Fe(CN)₆]? (Z for Fe = 26)
- A. 38
- B. 35
- C. 36
- D. 23
Q9. Which form of commercial iron has the highest carbon content?
- A. Cast iron
- B. Stainless steel
- C. Wrought iron
- D. Mild steel
Q10. A scratch exposes the iron under a tin coating on a tin-plated can in damp air. What happens to the iron?
- A. It is protected because tin is more reactive
- B. It does not corrode because the tin oxide layer seals the scratch
- C. It is protected because tin acts as a sacrificial anode
- D. It corrodes faster because iron becomes the anode of a cell with tin
Q11. In the blast furnace Fe₂O₃ + 3CO → 2Fe + 3CO₂. What mass of CO is needed to reduce 160 kg of Fe₂O₃ completely? (Fe = 56, O = 16, C = 12)
- A. 168 kg
- B. 56 kg
- C. 28 kg
- D. 84 kg
Q12. What is the equivalent mass of KMnO₄ (M = 158) when it acts as an oxidizing agent in neutral solution (MnO₄⁻ → MnO₂)?
- A. 52.7
- B. 79
- C. 158
- D. 31.6
Q13. In acid solution manganate ion disproportionates: 3MnO₄²⁻ + 4H⁺ → 2MnO₄⁻ + MnO₂ + 2H₂O. What fraction of the manganese(VI) ends up as permanganate?
- A. 2/3
- B. 1/2
- C. 3/4
- D. 1/3
Q14. 1 mol of N₂ and 3 mol of H₂ are mixed in the Haber process. At equilibrium 10% of the N₂ has reacted. What is the mole fraction of NH₃ in the mixture?
- A. 0.026
- B. 0.20
- C. 0.053
- D. 0.10
Q15. Fertilizer value is expressed as % P₂O₅ equivalent. What is it for pure triple superphosphate, Ca(H₂PO₄)₂ (M = 234)? (P₂O₅ = 142)
- A. 42.7%
- B. 60.7%
- C. 26.5%
- D. 30.3%
Q16. A fuel is made by mixing 70% iso-octane and 30% n-heptane by volume. What is its octane number?
- A. 100
- B. 30
- C. 85
- D. 70
Q17. Which statement correctly distinguishes photochemical smog from London (classical) smog?
- A. Photochemical smog forms at night from SO₂ and fog; London smog needs sunlight, NOₓ and hydrocarbons
- B. Photochemical smog is reducing and contains SO₂ and soot; London smog is oxidizing and contains O₃ and PAN formed in sunlight
- C. Both contain mainly SO₂ and soot, and both are oxidizing smogs that form in warm, sunny weather
- D. Photochemical smog contains O₃ and PAN formed from NOₓ and hydrocarbons in sunlight; London smog contains SO₂ and soot and is reducing
Q18. Among the 3d elements, zinc has the lowest melting point because
- A. it has the largest atomic radius of the 3d series, so its metallic bonds are the weakest
- B. it has no s electrons available, so only weak d–d bonding holds the lattice together
- C. its d subshell is full, so there are no unpaired d electrons for metallic bonding
- D. its first ionization energy is the lowest in the series, so it forms very few metallic bonds
Q19. Which catalyst is used for the hydrogenation of vegetable oils to make ghee?
- A. V₂O₅
- B. Finely divided iron
- C. Platinum–rhodium gauze
- D. Finely divided nickel
Q20. Which statement about interstitial compounds of transition metals such as TiC and Fe₃C is NOT correct?
- A. They retain metallic conductivity and a metallic lustre
- B. They are soft and have lower melting points than the parent metal
- C. They are chemically inert and unreactive towards most reagents
- D. They are very hard, which makes them useful for cutting tools
Q21. Zirconium and hafnium have almost identical atomic radii and similar chemistry. The cause is
- A. lanthanoid contraction from the poor shielding of 4f electrons
- B. the presence of 5s electrons only in the outer shell
- C. the inert pair effect shown by the heavier d-block elements
- D. hydrogen bonding between the oxides of the two elements
Q22. What is the crystal field stabilization energy (CFSE) of a low-spin d⁶ ion in an octahedral field, ignoring pairing energy?
- A. −2.4 Δₒ
- B. −1.2 Δₒ
- C. −0.4 Δₒ
- D. −0.6 Δₒ
Q23. [Co(NH₃)₅(NO₂)]²⁺ and [Co(NH₃)₅(ONO)]²⁺ are an example of which type of isomerism?
- A. Coordination isomerism
- B. Linkage isomerism
- C. Geometrical isomerism
- D. Ionization isomerism
Q24. Which reagent distinguishes [Co(NH₃)₅SO₄]Br from [Co(NH₃)₅Br]SO₄ by giving a precipitate with only one of them?
- A. BaCl₂ solution, which precipitates BaSO₄ only from the first
- B. AgNO₃ solution, which precipitates AgBr only from the second
- C. NaOH solution, which precipitates Co(OH)₃ from both
- D. AgNO₃ solution, which precipitates AgBr only from the first
Q25. In the manufacture of urea 2NH₃ + CO₂ → NH₂COONH₄ → CO(NH₂)₂ + H₂O. What mass of urea (M = 60) can be made from 34 kg of NH₃, assuming complete conversion? (N = 14, H = 1)
- A. 120 kg
- B. 30 kg
- C. 60 kg
- D. 34 kg
Q26. What mass of FeSO₄ (M = 152) is oxidized to Fe₂(SO₄)₃ in acid by 1.58 g of KMnO₄ (M = 158)?
- A. 1.52 g
- B. 15.2 g
- C. 7.6 g
- D. 3.8 g
Q27. Excess ammonia is added to aqueous copper(II) sulphate. What is the deep-blue species formed and its shape?
- A. [Cu(NH₃)₄]²⁺, tetrahedral
- B. [Cu(NH₃)₆]²⁺, octahedral
- C. Cu(OH)₂, square planar
- D. [Cu(NH₃)₄]²⁺, square planar
Q28. In the Haber process, K₂O and Al₂O₃ are added to the iron catalyst. Their role is as
- A. dehydrating agents that remove water from the NH₃
- B. reactants that supply extra nitrogen to the gas mixture
- C. poisons that reduce unwanted side reactions of NH₃
- D. promoters that increase the activity of the catalyst
Q29. In the stratosphere, chlorine atoms from CFCs destroy ozone in a chain: Cl + O₃ → ClO + O₂, then ClO + O → Cl + O₂. What is the role of chlorine?
- A. A catalyst that is regenerated and destroys many O₃ molecules
- B. An inhibitor that absorbs UV light
- C. A reactant consumed in a 1 : 1 ratio with O₃
- D. A product that forms ozone
Q30. The ratio of Fe²⁺ to Fe³⁺ ions in magnetite, Fe₃O₄, is
- A. 1 : 1
- B. 1 : 2
- C. 3 : 1
- D. 2 : 1