ECAT — Engineering College Admission Test (UET)
Take the ECAT Chemistry — Transition Elements and Industrial Chemistry (Set 5): 30 multiple-choice questions (40 minutes) with instant scoring and a full…
What this test covers
The first 5 questions of this test, with the correct answer and explanation.
Q1. Using the spin-only formula μ = √[n(n + 2)] BM, the magnetic moment of the high-spin octahedral complex [CoF₆]⁴⁻ (Co²⁺, d⁷) is
Answer: A. 3.87 BM
Explanation: High-spin d⁷: t₂g⁵ eg² has 3 unpaired electrons. μ = √(3 × 5) = √15 = 3.87 BM.
Q2. The crystal field stabilisation energy of a low-spin octahedral d⁷ ion (t₂g⁶ eg¹), ignoring pairing energy, is
Answer: B. −1.8 Δₒ
Explanation: CFSE = 6(−0.4Δₒ) + 1(+0.6Δₒ) = −2.4Δₒ + 0.6Δₒ = −1.8Δₒ. (High-spin d⁷ would be −0.8Δₒ.)
Q3. [Ti(H₂O)₆]³⁺ absorbs light most strongly at 500 nm. What is the crystal field splitting Δₒ in kJ mol⁻¹? (h = 6.626 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m s⁻¹, Nₐ = 6.022 × 10²³)
Answer: C. 239 kJ mol⁻¹
Explanation: E per photon = hc/λ = 3.97 × 10⁻¹⁹ J. Per mole: × 6.022e23 = 2.39 × 10⁵ J = 239 kJ mol⁻¹.
Q4. The complex ion [Co(en)₂Cl₂]⁺ (en = ethane-1,2-diamine, a bidentate ligand) is octahedral. How many stereoisomers does it have in total?
Answer: C. 3
Explanation: The trans isomer is achiral (one form). The cis isomer is chiral and exists as a pair of enantiomers. Total = 1 + 2 = 3.
Q5. The complex [Co(NH₃)₅Cl]Cl₂ ionises in water to give one complex cation and two free Cl⁻. If excess AgNO₃ is added to a solution containing 0.0100 mol of the complex, what mass of AgCl precipitates? (Ag = 108, Cl = 35.5)
Answer: B. 2.87 g
Explanation: Only the two free chloride ions precipitate (the Cl bound to Co is held as a ligand): 0.0200 mol × 143.5 = 2.87 g.
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Q6. In a blast furnace, Fe₂O₃ is reduced by CO: Fe₂O₃ + 3CO → 2Fe + 3CO₂. What mass of CO₂ is produced when 80 kg of Fe₂O₃ (M = 160) is reduced completely? (C = 12, O = 16)
Q7. Which of the following alloys has aluminium as its main constituent?
Q8. Rust may be represented as Fe₂O₃·H₂O (M = 178 g mol⁻¹). If an iron nail (Fe = 56) of mass 11.2 g is completely converted to rust, the mass of rust formed is
Q9. In acid solution Cr₂O₇²⁻ oxidises Fe²⁺ to Fe³⁺ (Cr₂O₇²⁻ → 2Cr³⁺). What mass of FeSO₄·7H₂O (M = 278) is oxidised by 0.0100 mol of K₂Cr₂O₇?
Q10. The equivalent mass of KMnO₄ (M = 158) when it acts as an oxidising agent in neutral medium, with MnO₄⁻ → MnO₂, is
Q11. What volume of 0.020 mol dm⁻³ KMnO₄ (acidified) is required to titrate 0.67 g of sodium oxalate, Na₂C₂O₄ (M = 134)? (2MnO₄⁻ + 5C₂O₄²⁻ + 16H⁺ → 2Mn²⁺ + 10CO₂ + 8H₂O)
Q12. How many cubic metres of H₂ at STP (22.4 dm³ mol⁻¹) are needed, by N₂ + 3H₂ → 2NH₃ with 100 % conversion, to make 1.00 tonne (10⁶ g) of NH₃ (17 g mol⁻¹)?
Q13. In the contact process, sulphur is converted to H₂SO₄ in three stages (S → SO₂ → SO₃ → H₂SO₄). If the overall efficiency is 95 %, the mass of H₂SO₄ (98 g mol⁻¹) obtainable from 32 kg of sulphur (32 g mol⁻¹) is
Q14. Fertiliser grades quote phosphorus as the % of P₂O₅. What is the P₂O₅ content of pure triple superphosphate, Ca(H₂PO₄)₂ (M = 234)? (P₂O₅ = 142)
Q15. A cement plant makes clinker containing 65 % CaO by mass, all derived from limestone CaCO₃ (CaCO₃ → CaO + CO₂). What mass of pure limestone is needed per 1000 kg of clinker? (Ca = 40, C = 12, O = 16)
Q16. A C₁₀H₂₂ molecule is thermally cracked into butane, C₄H₁₀, and one other hydrocarbon. What is the molecular formula of that second product?
Q17. Rain is naturally acidic because of dissolved CO₂. Taking [CO₂(aq)] = 0.034 × p(CO₂) with p(CO₂) = 4.2 × 10⁻⁴ atm, and Ka₁ of H₂CO₃ = 4.3 × 10⁻⁷, the pH of unpolluted rain is nearest to
Q18. In the destruction of stratospheric ozone by chlorine atoms (Cl• + O₃ → ClO• + O₂; ClO• + O → Cl• + O₂), the chlorine atom acts as
Q19. In the kraft (sulphate) pulping process for paper, wood chips are digested in a liquor containing
Q20. Zinc (Z = 30) is usually not classed as a transition element because
Q21. Mn(VI) in the manganate ion MnO₄²⁻ and Mn(VII) in MnO₄⁻ differ in their magnetic behaviour. Which statement is correct?
Q22. Ziegler–Natta catalysts, a mixture of TiCl₄ and Al(C₂H₅)₃, are used industrially to
Q23. Zirconium (Z = 40) and hafnium (Z = 72) have almost identical atomic radii, and so very similar chemistry. This is a consequence of
Q24. Anhydrous copper(II) sulphate is white but the pentahydrate is blue because in the hydrate
Q25. Cementite is the iron carbide Fe₃C found in steels. What is the mass percentage of carbon in pure Fe₃C? (Fe = 56, C = 12)
Q26. In the iron catalyst used in the Haber process, Al₂O₃ is added as a
Q27. The effective atomic number (EAN) of the central metal in K₂[PtCl₆] (Pt, Z = 78) is
Q28. [Co(NH₃)₅Br]SO₄ and [Co(NH₃)₅SO₄]Br are ionisation isomers. Which reagent distinguishes them most directly?
Q29. [Ni(en)₃]²⁺ is more stable than [Ni(NH₃)₆]²⁺ mainly because
Q30. In a blast furnace, silica impurity is removed as slag by CaO derived from limestone: SiO₂ + CaO → CaSiO₃. What mass of CaCO₃ is needed to slag 120 kg of SiO₂? (Si = 28, Ca = 40, C = 12, O = 16)