ECAT — Engineering College Admission Test (UET)
Take the ECAT Chemistry — Transition Elements and Industrial Chemistry (Set 7): 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 Ni²⁺ ion (Z = 28 for Ni) in a high-spin octahedral complex is:
Answer: A. 2.83 BM
Explanation: Ni²⁺ is 3d⁸ with 2 unpaired electrons: μ = √(2 × 4) = √8 = 2.83 BM.
Q2. Which of the following aqueous ions is colourless (Ti Z = 22, Cr 24, Fe 26, Co 27)?
Answer: B. Ti⁴⁺
Explanation: Ti⁴⁺ has the configuration [Ar] (3d⁰), so there are no d electrons for d–d transitions. Cr³⁺, Fe³⁺ and Co²⁺ have partially filled d subshells.
Q3. Which of the following species contains a transition element in the highest oxidation state (VO₂⁺, CrO₄²⁻, MnO₄⁻, FeO₄²⁻ with Fe taken as +6)?
Answer: D. MnO₄⁻ (+7)
Explanation: Oxidation numbers: V = +5, Cr = +6, Mn = +7, Fe = +6. Mn in permanganate has the highest value.
Q4. 25.0 cm³ of Fe²⁺ solution is oxidised by 15.0 cm³ of 0.020 M K₂Cr₂O₇ in acidic solution (Cr₂O₇²⁻ → Cr³⁺, Fe²⁺ → Fe³⁺). The molarity of Fe²⁺ is:
Answer: A. 0.072 M
Explanation: Cr₂O₇²⁻ = 0.300 mmol, which takes 6 Fe²⁺ each: 1.80 mmol Fe²⁺ in 25.0 cm³ = 0.072 M.
Q5. 25.0 cm³ of a Cu²⁺ solution is treated with excess KI (2Cu²⁺ + 4I⁻ → 2CuI + I₂). The I₂ liberated needs 20.0 cm³ of 0.100 M Na₂S₂O₃ (I₂ + 2S₂O₃²⁻ → 2I⁻ + S₄O₆²⁻). The molarity of Cu²⁺ is:
Answer: B. 0.080 M
Explanation: S₂O₃²⁻ = 2.00 mmol → I₂ = 1.00 mmol → Cu²⁺ = 2.00 mmol (2Cu²⁺ per I₂); 2.00 mmol/25.0 cm³ = 0.080 M.
Take the timed test (free, no sign-up) to see your score and the answer and explanation for every question.
Q6. Excess AgNO₃ solution is added to a solution containing 1 mol of [Co(NH₃)₅Cl]Cl₂. How many moles of AgCl are precipitated?
Q7. The complex ion [Co(en)₃]³⁺ contains three molecules of ethylenediamine (en, H₂NCH₂CH₂NH₂), each bonding through both nitrogen atoms. The coordination number of cobalt is:
Q8. The charge on the complex ion in K₄[Fe(CN)₆], and the oxidation state of iron in it, are respectively:
Q9. An iron ore contains 80% Fe₂O₃ by mass (Fe = 56, O = 16). Assuming complete reduction, the mass of iron obtainable from 1000 kg of this ore is:
Q10. In the basic oxygen steel-making process, acidic oxides such as SiO₂ and P₄O₁₀ from the pig iron are removed as slag by adding which flux?
Q11. For N₂ + 3H₂ ⇌ 2NH₃ (ΔH = −92 kJ mol⁻¹), which set of conditions gives the highest EQUILIBRIUM yield of ammonia?
Q12. In the Ostwald process, 4NH₃ + 5O₂ → 4NO + 6H₂O, then NO is converted finally to HNO₃ with the overall relation 1 mol NH₃ → 1 mol HNO₃ (N = 14, H = 1, O = 16). The mass of HNO₃ obtainable from 3.4 kg of NH₃ at 100% efficiency is:
Q13. In the contact process, 32 g of sulphur is converted to H₂SO₄ with an overall yield of 90% (S = 32, H₂SO₄ = 98 g mol⁻¹). The mass of H₂SO₄ produced is:
Q14. The nitrogen content of ammonium nitrate (80 g mol⁻¹) is 35% and that of urea (60 g mol⁻¹) is 46.7%. What mass of urea supplies the same mass of nitrogen as 100 kg of ammonium nitrate?
Q15. Superphosphate is made by Ca₃(PO₄)₂ + 2H₂SO₄ → Ca(H₂PO₄)₂ + 2CaSO₄ (Ca₃(PO₄)₂ = 310 g mol⁻¹; H₂SO₄ = 98 g mol⁻¹). The mass of H₂SO₄ needed for 31 g of Ca₃(PO₄)₂ is:
Q16. A small amount of gypsum is added to cement clinker during grinding in order to:
Q17. In thermal cracking, dodecane, C₁₂H₂₆, splits into octane and one other hydrocarbon. The other product is:
Q18. In the rusting of iron, the anodic reaction at the site of corrosion is:
Q19. Which of the following alloys contains NO copper?
Q20. In acidic solution Cr₂O₇²⁻ is reduced to Cr³⁺ (Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O). The equivalent mass of K₂Cr₂O₇ (294 g mol⁻¹) in this reaction is:
Q21. Aqueous orange potassium dichromate is made distinctly alkaline with NaOH. The colour changes to:
Q22. When aqueous ammonia is added drop by drop to CuSO₄ solution, a pale blue precipitate forms first and then dissolves in excess ammonia to give:
Q23. Zinc dissolves in hot concentrated NaOH: Zn + 2NaOH + 2H₂O → Na₂[Zn(OH)₄] + H₂ (Zn = 65). The volume of H₂ at STP (molar volume 22.4 dm³ mol⁻¹) from 6.5 g of zinc is:
Q24. In the cyanide process for gold, 4Au + 8NaCN + O₂ + 2H₂O → 4Na[Au(CN)₂] + 4NaOH. The gold is then recovered from the solution by adding:
Q25. In the electrolytic refining of copper, a current of 2.0 A flows for 9650 s through CuSO₄ solution (Cu = 63.5, F = 96 500 C mol⁻¹). The mass of copper deposited on the pure cathode is:
Q26. In the Hall–Héroult process the net change is 2Al₂O₃ + 3C → 4Al + 3CO₂ (Al = 27, C = 12). The mass of carbon anode consumed when 54 g of Al is produced is:
Q27. Finely divided nickel is used industrially as a catalyst for:
Q28. Which of the following 3d elements shows only one oxidation state (+3) in its compounds?
Q29. Chlorofluorocarbons deplete stratospheric ozone through the reactions Cl· + O₃ → ClO· + O₂ and ClO· + O → Cl· + O₂. In this sequence the chlorine atom acts as:
Q30. How many electrons are present in the 4s subshell of an Fe²⁺ ion in its ground state (Fe: Z = 26)?