ECAT — Engineering College Admission Test (UET)

ECAT Chemistry — Solutions and Electrochemistry (Set 1)

Take the ECAT Chemistry — Solutions and Electrochemistry (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. 4 g of NaOH is dissolved in water to make 250 cm³ of solution. Its molarity is:
- A. 0.4 M ✓
- B. 1.6 M
- C. 0.1 M
- D. 0.016 M
Answer: A. 0.4 M
Explanation: Moles = 4/40 = 0.1 mol; molarity = 0.1 mol / 0.25 dm³ = 0.4 M.
Q2. 9 g of glucose (C₆H₁₂O₆, M = 180) is dissolved in 500 g of water. The molality of the solution is:
- A. 0.2 m
- B. 0.05 m
- C. 0.018 m
- D. 0.1 m ✓
Answer: D. 0.1 m
Explanation: Moles = 9/180 = 0.05 mol; molality = 0.05 mol / 0.5 kg = 0.1 mol kg⁻¹.
Q3. 46 g of ethanol (C₂H₅OH) is mixed with 54 g of water. The mole fraction of ethanol is:
- A. 0.25 ✓
- B. 0.75
- C. 0.46
- D. 0.33
Answer: A. 0.25
Explanation: Ethanol = 46/46 = 1 mol, water = 54/18 = 3 mol; x(ethanol) = 1/(1 + 3) = 0.25.
Q4. 50 cm³ of 2 M HCl is diluted with water to 500 cm³. The molarity of the diluted solution is:
- A. 0.2 M ✓
- B. 20 M
- C. 0.02 M
- D. 0.5 M
Answer: A. 0.2 M
Explanation: M₁V₁ = M₂V₂: M₂ = 2 × 50/500 = 0.2 M.
Q5. 10 g of NaCl is dissolved in 90 g of water. The percentage by mass (w/w) of NaCl is:
- A. 10% ✓
- B. 9%
- C. 11.1%
- D. 90%
Answer: A. 10%
Explanation: % w/w = mass of solute / mass of solution × 100 = 10/(10 + 90) × 100 = 10%.

The other 25 questions

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Q6. The vapour pressure of a pure solvent is 100 torr. A non-volatile solute is added so that its mole fraction is 0.2. The vapour pressure of the solution is:
- A. 80 torr
- B. 20 torr
- C. 120 torr
- D. 100 torr
Q7. For a dilute solution of a non-volatile solute, the relative lowering of vapour pressure is equal to:
- A. the molarity of the solution
- B. the mole fraction of the solvent
- C. the molality of the solution
- D. the mole fraction of the solute
Q8. A 0.5 m aqueous solution of urea boils at (Kb of water = 0.52 K kg mol⁻¹):
- A. 100.26°C
- B. 100.52°C
- C. 100.13°C
- D. 99.74°C
Q9. Assuming complete dissociation, a 1 m aqueous NaCl solution freezes at (Kf of water = 1.86 K kg mol⁻¹):
- A. −1.86°C
- B. −5.58°C
- C. −0.93°C
- D. −3.72°C
Q10. Which 0.1 m aqueous solution has the lowest freezing point?
- A. urea
- B. glucose
- C. CaCl₂
- D. NaCl
Q11. 2 g of a non-electrolyte dissolved in 100 g of water lowers the freezing point by 0.186 K (Kf = 1.86 K kg mol⁻¹). The molar mass of the solute is:
- A. 372 g mol⁻¹
- B. 100 g mol⁻¹
- C. 200 g mol⁻¹
- D. 20 g mol⁻¹
Q12. An ideal solution is one for which:
- A. the volume always decreases on mixing
- B. ΔH(mixing) is negative
- C. ΔH(mixing) = 0 and ΔV(mixing) = 0
- D. Raoult's law is obeyed only by the solute
Q13. A mixture of ethanol and water shows positive deviation from Raoult's law. Such a mixture forms:
- A. an ideal solution
- B. a mixture that can be completely separated by simple fractional distillation
- C. a minimum-boiling azeotrope
- D. a maximum-boiling azeotrope
Q14. An aqueous solution of Na₂CO₃ is basic because:
- A. Na⁺ ions produce OH⁻ ions
- B. Na₂CO₃ does not dissolve in water
- C. CO₃²⁻ ions undergo hydrolysis to produce OH⁻ ions
- D. carbonic acid is a strong acid
Q15. Which substance becomes LESS soluble in water as the temperature rises?
- A. KCl
- B. KNO₃
- C. NaNO₃
- D. Ce₂(SO₄)₃
Q16. The percentage of water of crystallization in CuSO₄·5H₂O (Cu = 63.5) is about:
- A. 64.0%
- B. 36.1%
- C. 56.4%
- D. 18.0%
Q17. The oxidation number of manganese in K₂MnO₄ is:
- A. +6
- B. +4
- C. +2
- D. +7
Q18. The oxidation number of sulphur in sodium thiosulphate, Na₂S₂O₃, is (average value):
- A. +4
- B. +6
- C. +2
- D. −2
Q19. Water acidified with a little H₂SO₄ is electrolysed using platinum electrodes. The ratio of the volumes of H₂ and O₂ collected is:
- A. 1 : 1
- B. 2 : 1
- C. 4 : 1
- D. 1 : 2
Q20. How long must a current of 10 A flow to deposit 2.7 g of aluminium from Al³⁺ ions (Al = 27, 1 F = 96500 C)?
- A. 1930 s
- B. 2895 s
- C. 8685 s
- D. 965 s
Q21. How much charge is needed to deposit 10.8 g of silver from AgNO₃ solution (Ag = 108)?
- A. 96500 C
- B. 965 C
- C. 9650 C
- D. 19300 C
Q22. A galvanic cell is made from Mg²⁺/Mg (E° = −2.37 V) and Cu²⁺/Cu (E° = +0.34 V) half-cells. Its standard emf is:
- A. 2.71 V
- B. −2.71 V
- C. 2.03 V
- D. 0.34 V
Q23. Which of the following is the strongest reducing agent in aqueous solution?
- A. Zn
- B. Na
- C. Li
- D. Cu
Q24. The standard hydrogen electrode (SHE) has:
- A. an electrode potential of +1.00 V
- B. hydrogen gas at 10 atm pressure
- C. a copper electrode dipped in 1 M H⁺
- D. an electrode potential taken as zero by convention
Q25. In a galvanic cell, oxidation takes place at the:
- A. cathode, which is the negative electrode
- B. anode, which is the positive electrode
- C. cathode, which is the positive electrode
- D. anode, which is the negative electrode
Q26. Which metal can displace copper from aqueous CuSO₄?
- A. Ag
- B. Au
- C. Pt
- D. Zn
Q27. In acidic solution, MnO₄⁻ oxidizes Fe²⁺ to Fe³⁺. How many moles of Fe²⁺ are oxidized by 1 mol of MnO₄⁻?
- A. 1
- B. 3
- C. 2
- D. 5
Q28. When a lead storage battery discharges:
- A. the density of H₂SO₄ increases
- B. lead is deposited at the cathode
- C. PbSO₄ forms at both electrodes and the acid becomes more dilute
- D. PbO₂ forms at both electrodes
Q29. In a hydrogen–oxygen fuel cell, the overall product is:
- A. hydroxide ions only
- B. hydrogen peroxide
- C. ozone
- D. water
Q30. Given E°(Ag⁺/Ag) = +0.80 V and E°(Zn²⁺/Zn) = −0.76 V, the standard emf of the cell Zn | Zn²⁺ || Ag⁺ | Ag is:
- A. 1.56 V
- B. 0.04 V
- C. 0.84 V
- D. 2.36 V