ECAT — Engineering College Admission Test (UET)
Take the ECAT Chemistry — Gases, Liquids and Solids (Set 2): 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. A gas at 2 atm occupies 3 dm³. At constant temperature its pressure is lowered to 1.5 atm. Its new volume is:
Answer: D. 4 dm³
Explanation: Boyle's law: P₁V₁ = P₂V₂ → V₂ = 2 × 3 / 1.5 = 4 dm³.
Q2. 400 cm³ of a gas at 127°C is cooled at constant pressure until its volume becomes 300 cm³. The final temperature is:
Answer: C. 27°C
Explanation: T₁ = 400 K; T₂ = T₁V₂/V₁ = 400 × 300/400 = 300 K = 27°C.
Q3. How many moles of an ideal gas occupy 4.1 dm³ at 3 atm and 300 K (R = 0.0821 dm³ atm K⁻¹ mol⁻¹)?
Answer: A. 0.5 mol
Explanation: n = PV/RT = 3 × 4.1 / (0.0821 × 300) ≈ 0.50 mol.
Q4. 1.6 g of a gas occupies 1.12 dm³ at STP. Its molar mass is:
Answer: A. 32 g mol⁻¹
Explanation: Moles = 1.12/22.4 = 0.05 mol; M = 1.6/0.05 = 32 g mol⁻¹.
Q5. The density of O₂ gas at 27°C and 1 atm is about (R = 0.0821 dm³ atm K⁻¹ mol⁻¹):
Answer: B. 1.30 g dm⁻³
Explanation: d = PM/RT = 1 × 32 / (0.0821 × 300) ≈ 1.30 g dm⁻³ (lower than 1.43 g dm⁻³ at STP because the gas is warmer).
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Q6. Under identical conditions, how does the rate of diffusion of CH₄ compare with that of SO₂?
Q7. A vessel contains 0.2 mol of N₂ and 0.3 mol of O₂ at a total pressure of 5 atm. The partial pressure of O₂ is:
Q8. A gas is collected over water at 25°C when the barometer reads 760 torr. The aqueous tension at 25°C is 24 torr. The pressure of the dry gas is:
Q9. The total translational kinetic energy of 1 mol of an ideal gas at 300 K is about (R = 8.314 J K⁻¹ mol⁻¹):
Q10. The root-mean-square speed of O₂ molecules at 27°C is about (R = 8.314 J K⁻¹ mol⁻¹):
Q11. At what temperature will SO₂ molecules have the same root-mean-square speed as O₂ molecules at 27°C?
Q12. For a real gas, a compressibility factor Z = PV/nRT less than 1 indicates that:
Q13. In the van der Waals equation, the term an²/V² is added to the observed pressure in order to correct for:
Q14. Which gas has the highest critical temperature and is therefore the easiest to liquefy?
Q15. At constant temperature, a graph of PV against P for an ideal gas is:
Q16. Evaporation of a liquid causes cooling because:
Q17. Glycerol is purified by distillation under reduced pressure because:
Q18. HF boils at about 19°C, higher than HCl (−85°C), but lower than H₂O (100°C). Why is the boiling point of water higher than that of HF?
Q19. Glycerol (propane-1,2,3-triol) is much more viscous than ethanol mainly because:
Q20. When a liquid crystal is heated, the temperature at which its turbid fluid becomes a clear, isotropic liquid is called the:
Q21. The number of atoms per unit cell and the coordination number in a face-centred cubic (fcc) lattice are respectively:
Q22. A metal crystallizes in an fcc lattice with an edge length of 400 pm; the atoms touch along the face diagonal. Its atomic radius is about:
Q23. Copper (M = 63.5) has an fcc lattice with edge length 361 pm. Its density is about (Nₐ = 6.02 × 10²³ mol⁻¹):
Q24. Which property distinguishes glass (an amorphous solid) from a crystalline solid such as quartz?
Q25. Graphite conducts electricity along its layers because:
Q26. K₂SO₄ and K₂SeO₄ have similar formulae and crystallize with the same crystal structure. This phenomenon is called:
Q27. Graphite, zinc and magnesium crystallize in a system whose unit cell has two equal axes at 120° to each other and a third, unequal axis perpendicular to both. This system is:
Q28. At the same temperature and pressure, 2 dm³ of H₂ and 2 dm³ of CO₂ contain:
Q29. Metals conduct electricity in the solid state because:
Q30. Which statement about the fourth state of matter, plasma, is correct?