ECAT — Engineering College Admission Test (UET)
Take the ECAT Chemistry — Solutions and Electrochemistry (Set 3): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer review.…
What this test covers
The first 5 questions of this test, with the correct answer and explanation.
Q1. Concentrated HCl is 37% by mass with density 1.19 g/mL (HCl = 36.5). Its molarity is approximately:
Answer: C. 12.1 M
Explanation: M = (% × d × 10)/M₀ = (37 × 1.19 × 10)/36.5 = 12.1 M.
Q2. 200 mL of 0.5 M NaCl is mixed with 300 mL of 1.0 M NaCl. The molarity of the mixture is:
Answer: B. 0.8 M
Explanation: Moles = 0.1 + 0.3 = 0.4 in 0.5 L: 0.8 M.
Q3. 20 g of NaOH (40 g/mol) is dissolved in 500 g of water. The molality of the solution is:
Answer: A. 1.0 m
Explanation: n = 20/40 = 0.5 mol; mass of solvent = 0.5 kg; m = 0.5/0.5 = 1.0 mol/kg.
Q4. The mole fraction of ethanol in a mixture of 46 g ethanol (C₂H₅OH) and 54 g of water is:
Answer: B. 0.25
Explanation: n(ethanol) = 1 mol; n(water) = 3 mol; X = 1/4 = 0.25.
Q5. 6 g of urea (60 g/mol) is dissolved in 100 g of water (Kb = 0.52 K kg mol⁻¹). The boiling point elevation is:
Answer: B. 0.52 K
Explanation: m = 0.1/0.1 = 1 mol/kg; ΔTb = 0.52 × 1 = 0.52 K.
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Q6. The expected freezing point of 0.1 m aqueous CaCl₂ (Kf = 1.86 K kg mol⁻¹, complete dissociation) is:
Q7. The osmotic pressure of a 0.1 M non-electrolyte solution at 27 °C is (R = 0.0821 L atm K⁻¹ mol⁻¹):
Q8. A glucose solution isotonic with 0.1 M NaCl (assume complete ionisation) has a concentration of:
Q9. An ideal mixture has equal moles of liquid A (P° = 75 torr) and liquid B (P° = 25 torr) at a given temperature. The mole fraction of A in the vapour over the liquid is:
Q10. When 0.1 mol of a non-volatile solute is dissolved in 9.9 mol of a solvent, the relative lowering of vapour pressure is:
Q11. According to Henry's law, the solubility of a gas in a liquid at constant temperature is:
Q12. Acetic acid dissolved in benzene shows an observed molar mass of about 120 instead of 60 because:
Q13. The oxidation state of sulphur in the tetrathionate ion S₄O₆²⁻ is:
Q14. The oxidation number of chromium in CrO₅ (which contains one oxo and two peroxo groups) is:
Q15. The oxidation number of iron in Fe₃O₄ is:
Q16. In the reaction Cl₂ + 2NaOH(cold, dilute) → NaCl + NaOCl + H₂O, chlorine is:
Q17. In acidic medium MnO₄⁻ oxidises Fe²⁺ to Fe³⁺ (MnO₄⁻ → Mn²⁺). What volume of 0.1 M FeSO₄ is oxidised by 20 mL of 0.02 M KMnO₄?
Q18. A current of 2 A is passed for 965 s through aqueous CuSO₄ using copper electrodes. The mass of copper deposited is (Cu = 63.5, F = 96500 C):
Q19. When a concentrated aqueous NaCl solution is electrolysed with inert electrodes, the products at the cathode and anode are respectively:
Q20. Electrolysis of aqueous CuSO₄ with platinum electrodes gives at the anode:
Q21. The cell Zn | Zn²⁺(0.1 M) || Cu²⁺(0.001 M) | Cu has E° = 1.10 V. Its EMF at 25 °C (0.0591/n log term) is:
Q22. The standard free energy change for a cell with n = 2 and E° = 1.10 V is (F = 96500 C/mol):
Q23. The E°cell for the reaction Cu + 2Ag⁺ → Cu²⁺ + 2Ag, given E°(Ag⁺/Ag) = +0.80 V and E°(Cu²⁺/Cu) = +0.34 V, is:
Q24. In a galvanic cell, the anode is the electrode at which:
Q25. During the discharge of a lead–acid storage battery:
Q26. Given Λ°m for HCl = 426, CH₃COONa = 91 and NaCl = 126 S cm² mol⁻¹, the Λ°m of CH₃COOH is:
Q27. A conductivity cell has a cell constant of 1.29 cm⁻¹ and the measured resistance of an electrolyte in it is 100 Ω. The conductivity κ is:
Q28. The pH of 0.1 M NH₄Cl solution (Kb of NH₃ = 1.8 × 10⁻⁵) is approximately:
Q29. The volume of 0.5 M NaOH needed to completely neutralise 0.1 mol of H₂SO₄ is:
Q30. Which of the following is the strongest reducing agent? (E° values: Li⁺/Li −3.05 V, Zn²⁺/Zn −0.76 V, Cu²⁺/Cu +0.34 V, Ag⁺/Ag +0.80 V)