ECAT — Engineering College Admission Test (UET)

ECAT Chemistry — Gases, Liquids and Solids (Set 1)

Take the ECAT Chemistry — Gases, Liquids and Solids (Set 1): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer review.…

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. A gas occupies 2 dm³ at 1 atm. At constant temperature it is compressed to 0.5 dm³. Its new pressure is:
- A. 2 atm
- B. 4 atm ✓
- C. 1.5 atm
- D. 0.25 atm
Answer: B. 4 atm
Explanation: Boyle's law: P₁V₁ = P₂V₂, so P₂ = 1 × 2/0.5 = 4 atm.
Q2. 600 cm³ of a gas at 300 K is heated to 450 K at constant pressure. Its new volume is:
- A. 900 cm³ ✓
- B. 400 cm³
- C. 750 cm³
- D. 1200 cm³
Answer: A. 900 cm³
Explanation: Charles's law: V₂ = V₁T₂/T₁ = 600 × 450/300 = 900 cm³.
Q3. The volume of 2 mol of an ideal gas at 27°C and 2 atm is about (R = 0.0821 dm³ atm K⁻¹ mol⁻¹):
- A. 49.3 dm³
- B. 24.6 dm³ ✓
- C. 4.4 dm³
- D. 12.3 dm³
Answer: B. 24.6 dm³
Explanation: V = nRT/P = 2 × 0.0821 × 300/2 = 24.6 dm³.
Q4. The density of CO₂ gas at STP is about:
- A. 0.98 g dm⁻³
- B. 1.96 g dm⁻³ ✓
- C. 1.43 g dm⁻³
- D. 44 g dm⁻³
Answer: B. 1.96 g dm⁻³
Explanation: Density = M/Vₘ = 44 g mol⁻¹ / 22.4 dm³ mol⁻¹ = 1.96 g dm⁻³.
Q5. A gas has a density of 2.5 g dm⁻³ at STP. Its molar mass is:
- A. 56 g mol⁻¹ ✓
- B. 28 g mol⁻¹
- C. 8.96 g mol⁻¹
- D. 112 g mol⁻¹
Answer: A. 56 g mol⁻¹
Explanation: M = d × 22.4 = 2.5 × 22.4 = 56 g mol⁻¹.

The other 25 questions

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Q6. Under the same conditions, the ratio of the rates of effusion of H₂ and O₂ is:
- A. 16 : 1
- B. 4 : 1
- C. 1 : 16
- D. 1 : 4
Q7. A gas takes twice as long as the same volume of O₂ to effuse under identical conditions. Its molar mass is:
- A. 16 g mol⁻¹
- B. 64 g mol⁻¹
- C. 45 g mol⁻¹
- D. 128 g mol⁻¹
Q8. A mixture of 4 g of H₂ and 32 g of O₂ has a total pressure of 3 atm. The partial pressure of H₂ is:
- A. 0.33 atm
- B. 2 atm
- C. 1 atm
- D. 1.5 atm
Q9. Which value of the gas constant R is expressed in dm³ torr K⁻¹ mol⁻¹?
- A. 1.987
- B. 8.314
- C. 0.0821
- D. 62.4
Q10. According to the kinetic molecular theory, the average kinetic energy of gas molecules depends only on:
- A. pressure
- B. molar mass
- C. volume
- D. absolute temperature
Q11. At the same temperature, the ratio of the root-mean-square speed of He to that of CH₄ is:
- A. 2 : 1
- B. 4 : 1
- C. 1 : 2
- D. 1 : 4
Q12. Real gases deviate most from ideal behaviour at:
- A. high pressure and low temperature
- B. low pressure and low temperature
- C. high temperature only
- D. low pressure and high temperature
Q13. The units of the van der Waals constant 'a' are:
- A. atm mol dm⁻³
- B. dm³ mol⁻¹
- C. atm dm³ mol⁻¹
- D. atm dm⁶ mol⁻²
Q14. Above its critical temperature, a gas:
- A. liquefies at 1 atm
- B. cannot be liquefied however much pressure is applied
- C. turns directly into a solid
- D. behaves as an ideal gas at all pressures
Q15. Linde's method of liquefying air is based on:
- A. heating of a gas on compression
- B. fractional distillation of liquid oxygen only
- C. absorption of air by charcoal
- D. cooling produced when a compressed gas expands (Joule–Thomson effect)
Q16. At constant pressure, a gas at 0°C is heated until its volume doubles. The final temperature is:
- A. 546°C
- B. 273°C
- C. 0°C
- D. 100°C
Q17. Water boils below 100°C at Murree because:
- A. the intermolecular forces in water are weaker there
- B. the air is colder
- C. the water contains dissolved salts
- D. the atmospheric pressure there is lower
Q18. H₂O boils at 100°C while H₂S boils at about −60°C. The main reason is:
- A. greater molar mass of H₂O
- B. weaker London forces in H₂S
- C. hydrogen bonding between H₂O molecules
- D. ionic bonding in H₂O
Q19. Which of the following has the highest boiling point?
- A. n-butane
- B. isopentane (2-methylbutane)
- C. neopentane (2,2-dimethylpropane)
- D. n-pentane
Q20. The vapour pressure of a pure liquid at a given temperature does NOT depend on:
- A. the surface area of the liquid
- B. the temperature
- C. the strength of intermolecular forces
- D. the nature of the liquid
Q21. A common everyday use of liquid crystals is in:
- A. the cores of electric transformers
- B. semiconductor chips of computers
- C. display screens of digital watches and calculators
- D. fuel for rocket engines
Q22. How many atoms belong to one unit cell of a body-centred cubic (bcc) lattice?
- A. 4
- B. 1
- C. 2
- D. 8
Q23. In a NaCl crystal, the coordination number of Na⁺ is:
- A. 8
- B. 12
- C. 4
- D. 6
Q24. In a CsCl crystal, each Cs⁺ ion is surrounded by:
- A. 6 Cl⁻ ions
- B. 8 Cl⁻ ions
- C. 12 Cl⁻ ions
- D. 4 Cl⁻ ions
Q25. Calcium carbonate occurs as both calcite and aragonite. A substance existing in more than one crystalline form shows:
- A. polymorphism
- B. isomorphism
- C. allotropy of elements only
- D. anisotropy
Q26. A crystal system with a = b ≠ c and α = β = γ = 90° is called:
- A. cubic
- B. hexagonal
- C. tetragonal
- D. orthorhombic
Q27. Which compound has the highest lattice energy?
- A. KCl
- B. CsI
- C. NaCl
- D. MgO
Q28. Iodine molecules in solid iodine are held together mainly by:
- A. covalent bonds
- B. hydrogen bonds
- C. London dispersion forces
- D. ionic bonds
Q29. 500 cm³ of a gas at 27°C and 760 torr is changed to 127°C and 380 torr. Its new volume is:
- A. 667 cm³
- B. 1333 cm³
- C. 1000 cm³
- D. 375 cm³
Q30. A metal crystallizes in a bcc lattice with edge length 400 pm. The atoms touch along the body diagonal. The atomic radius is about:
- A. 100 pm
- B. 200 pm
- C. 173 pm
- D. 141 pm