50 JAMB Repeated Questions in Chemistry and their Answers

This post is for JAMB candidates who are preparing to sit for Chemistry in their UTME examination. So I’m going to share the JAMB Repeated Questions in Chemistry with you and tell you few things you need to know about JAMB repeated questions. But beyond showing you the JAMB repeated questions in Chemistry, I will also give you the link to the entire JAMB Chemistry Past Questions and Answers PDF.

When I started receiving the question, “Does JAMB Repeat Past Their Questions papers?” on my various platforms, I made a post on this website where I authoritatively informed my readers that JAMB indeed repeats their past questions.

But when we think about Chemistry as a subject, we all acknowledge the fact that it is both vast and evolving. We know that JAMB can afford to set hundreds of new questions every year if they so wish.

However, JAMB repeats certain questions in Chemistry exams for reasons best known to them.

So I’m going to devote this post to showing you JAMB Most Repeated Questions in Chemistry. Of course, when you have insight into the questions JAMB repeats most, you will prepare better for them.

Importance of Gaining Insight into the JAMB Repeated Questions in Chemistry

Gaining insight into the JAMB Repeated Questions in Chemistry is very essential for your success in the forthcoming 2024 exams.

This is because when you see the most repeated Chemistry questions, you can tell which topics they are coming from. When you know the topics, you can do justice to them using your JAMB Recommended Textbooks. This is one of the secrets to effective preparation for JAMB.

The JAMB most repeated Chemistry questions are also the likely questions for 2024. So if you are looking for JAMB likely questions in Chemistry for 2024 UTME, read the questions on this post carefully. If you do, you will thank me later.

The JAMB Repeated Questions in Chemistry and their Answers

I am going to give you the JAMB most repeated questions in Chemistry in groups of 10. For each group, I will provide the answers as a guide for the candidates who may wish to do their revision on this platform.

JAMB Repeated Questions in Chemistry (1 – 10)

1. Two immiscible liquids with different boiling points can be separated by
A. the use of separating funnel
B. evaporation
C. distillation
D. decantation

2. A mixture of CaCl₂ and CaCO₃ in water can be separated by
A. evaporation              B. sublimation
C. distillation                D. decantation

3. Consider the reaction represented by
xPb(NO₃)₂ → 2PbO + yNO₂ + zO₂
What are the values of x, y and z respectively?
A. 2, 6, 3                 B. 1, 4, 2
C. 2, 4, 1                 D. 2, 4, 2

4. 20 cm³ of H₂ mixed and separated with 100 cm³ of air containing 21% O₂. Calculate the volume of the residual gases at 110 °C.
A. 31 cm³               B. 11 cm³
C. 90 cm³               D. 110 cm³

5. What is responsible for metallic bonding?
A. Sharing of electrons between the metal atoms
B. Attraction between the atomic nuclei and the cloud of electrons
C. Transfer of electrons from one atom to another
D. Attraction between positive and negative ions

6. 25 cm³ of 1.5 M solution of NaCl are added to 50 cm³ 0f 3 M NaCl. The molar concentration of the resulting solution is
A. 2.5 M                 B. 3 M
C. 2.25 M               D. 4.5 M

7. A solution of salt formed from HCl and NH₃ solutions is
A. acidic                  B. basic
C. complex             D. neutral

8. Which of the following elements will burn in excess oxygen to form a product that is neutral to litmus?
A. Carbon               B. Hydrogen
C. Sulphur              D. Sodium

9. A current was passed for 10 mins and 0.2 mole of Cu was deposited. How many grammes of Ag will it deposit?
(Cu = 64, Ag = 108)
A. 43.2 g               B. 21.6 g
C. 10.8 g               D. 5.4 g

10. Pollution of underground water by metal ions is very likely in a soil that has high
A. acidity
B. alkalinity
C. chloride content
D. nitrate content

Answers to JAMB Most Repeated Questions in Chemistry (1 – 10)

1.A         2.D        3.C       4.D        5.B
6.A         7.A        8.B       9.A        10.D

JAMB Repeated Questions in Chemistry (11 – 20)

11. What are the values of p, q, r and s respectively in the equation?
pCH₄ + qO₂ → rCO + sH₂O
A. 1, 2, 1, 2           B. 1, 3, 2, 2
C. 2, 3, 2, 4           D. 2, 3, 2, 2

12. KHCO₃ is contaminated with K₂CO₃ as impurity. If 2.5 g of the impure KHCO₃ on heating produces 0.224 dm³ of CO₂ at s.t.p., calculate the percentage of K₂CO₃ impurity.
(K = 39, H = 1, C = 12, O = 16)
A. 30%            B. 40%
C. 10%            D. 20%

13. The partial pressure of N₂ in a container at 50 °C in which there are 0.30 mole of N₂ and 1.2 mole of CO₂ at a pressure of 2.00 atm is?
A. 0.6 atm          B. 0.5 atm
C. 0.4 atm          D. 1.6 atm

14. The major reason why chemical reaction occurs among elements is that they have the tendency to
A. attain the nearest noble gas structure
B. become a metal
C. become a non-metal
D. become a noble element

15. Given that the pH of a solution of KOH is 12, what is the concentration of the OH^– ions?
A. 0.01 mol/dm³                B. 1 × 10^-12 mol/dm³
C. 1 × 10^-14 mol/dm³           D. 1 × 10^-7 mol/dm³

16. Which of the following salt has a pH less than 7?
A. NaHCO₃             B. NH₄Cl
C. Na₂SO₄              D. NaCl

17. In which of the following reactions does hydrogen peroxide act as a reducing agent?
A. PbO₂ + 2HNO₃ + H₂O₂ → Pb(NO₃)₂ + 2H₂O + O₂
B. H₂S + H₂O₂ → S + 2H₂O
C. PbSO₂ + H₂O₂ → PbSO₄ + H₂O
D. 2I^– + 2H⁺ + H₂O₂ → I₂ + 2H₂O

18. Temporary hardness of water is removed by the use of the following EXCEPT
A. Boiling
B. Use of Ca(OH)₂
C. Use of Na₂CO₃
D. Use of alum

19. Hydration of ions in solution is associated with
A. Liberation of heat          B. Absorption of heat
C. Reduction of heat          D. Conduction of heat

20. Which of the following pairs of substances are hygroscopic?
A. CaCl and NaOH
B. CaO and KOH
C. Conc. H₂SO₄ and MgCl₂
D. CuO and CaO

Answers to JAMB Most Repeated Questions in Chemistry (11 – 20)

11.A        12.D        13.B        14.A       15.A
16.A        17.A        18.D        19.A       20.D

JAMB Repeated Questions in Chemistry (21 – 30)

21. Crystallization is a better method of separation than precipitation because
A. precipitation tends to bring other solutes out of solution
B. crystallization is applicable to all solids
C. precipitation always involves salting-out
D. crystallization can only be done at high temperatures

22. Which of the following is not a chemical change?
A. burning of magnesium
B. rusting of iron
C. action of water on potassium
D. dissolving powdered sulfur in carbon disulfide

23. An important ore of iron contains 72.36% iron and 27.64% oxygen. Determine its empirical formula
A. FeO                 B. Fe₂O₃
C. Fe₃O₄              D. Fe₂O₂

24. Which of the following decreases when a given mass of gas is compressed to half its initial volume?
A. average intermolecular distance
B. frequency of collision
C. number of molecules present
D. atomic radius of each particle

25. The densities of two gases X and Y are 2.5gdm^-3 and 10.0gdm^-3 respectively. What is the rate of diffusion of X relative to Y?
A. 1:2.5            B. 2.5:1
C. 1:2               D. 2:1

26. The properties of elements are periodic functions of their
A. atomic number              B. atomic radius
C. atomic volume               D. mass number

27. Which of the following solutions containing only hydroxyl ions will liberate hydrogen gas when reacted with Mg metals?
A. 1.0 × 10^-5moldm^-3           B. 1.0 × 10^-13moldm^-3
C. 1.0 × 10^-3moldm^-3           D. 1.0 × 10^-2moldm^-3

28. In the redox reaction
2Fe²⁺ + Cl₂ → 2Fe³⁺ + 2Cl^–
A. Cl₂ is reduced because it has lost electrons
B. Cl₂ is reduced because its oxidation number has decreased
C. Fe²⁺ is reduced because it has lost electrons
D. Fe²⁺ is reduced because it has gained electrons

29. During electrolysis of molten sodium chloride,
A. chlorine atom gains an electron
B. chloride ion gains an electron
C. chloride ion is oxidized
D. sodium ion is oxidized

30. Coffee stains are removed with
A. turpentine                 B. ammonia
C. borax in water           D. kerosene

Answers to JAMB Most Repeated Questions in Chemistry (21 – 30)

21.A      22.D       23.A       24.A       25.D
26.A      27.B       28.B        29.C       30.C

JAMB Repeated Questions in Chemistry (31 – 40)

31. Addition of water to calcium oxide leads to
A. a physical change
B. a chemical change
C. the formation of a mixture
D. an endothermic reaction

32. 15 g of impure Na₂CO₃ reacted with excess HNO₃. If 0.1 mole of CO₂ is produced, what is the percentage purity of the Na₂CO₃? [Na = 23, C = 12, O = 16] A. 35.3%               B. 10.0%
C. 70.66%             D. 90.0%

33. 0.14 g of a hydride of carbon occupies 112.0 cm³ at STP when evaporated. The ratio of carbon to hydrogen is 1:2. The relative molecular formula is
A. C₂H₄            B. C₃H₆
C. C₄H₈            D. C₆H₁₂

34. A gas X diffuses twice as fast as a gas Y under the same conditions. If the relative molecular mass of Y is 112, calculate the relative molecular mass of X.
A. 28         B. 14        C. 56         D. 120

35. In the periodic table, what is the property that decreases along the period and increases down the group?
A. Atomic number           B. Electron affinity
C. Ionization potential     D. Ionic radius

36. 10 cm³ of 0.1 M HCl are added to 10 cm³ of NaOH solution containing 8 g of NaOH per dm³ of solution. What is the pH of the resulting solution?
A. 11        B. 13        C. 7        D. 8

37. What is the formular of sodium gallate if gallium (Ga) shows an oxidation number of +3?
A. NaGaO₃                B. Na₂Ga(OH)₂
C. NaGa(OH)₃           D. NaGa(OH)₄

38. The mass of Ag deposited when a current of 10 A is passed through a solution of silver salt for 4830 secs is [Ag = 108, 1F = 96500C] A. 54.0 g               B. 27.0 g
C. 13.5 g               D. 108.0 g

39. The solubility of alkanols in water is due to
A. their covalent nature
B. hydrogen bond
C. their low boiling point
D. their ionic character

40. If a reaction is exothermic and there is a great disorder, it means
A. the reaction is in a state of equilibrium
B. there will be a large increase in free energy
C. there will be a large decrease in free energy
D. the reaction is static

Answers to JAMB Most Repeated Questions in Chemistry (31 – 40)

31.B       32.C        33.A        34.A        35.D
36.A       37.D        38.A        39.B        40.C

JAMB Most Repeated Questions in Chemistry (41 – 50)

41. 2SO_2(g) + O_2(g)   →  2SO_3(g)      ΔH = -395.7kJmol^-1
In the reaction above, the concentration of SO_3(g) can be increased by
A. decreasing the pressure
B. decreasing the temperature
C. increasing the temperature
D. the addition of catalyst

42. Which of the following compounds is a normal salt?
A. Na₂CO₃             B. NaHSO₄
C. NaHCO₃            D. NaHS

43. Which of the following ions can be used as an oxidizing agent?
A. F^–                B. Fe³⁺
C. Au³⁺            D. Ca²⁺

44. CO_(g) + H₂O_(g)  →   CO_2(g) + H_2(g)
Calculate the standard heat change of the reaction above if the standard enthalpies of formation of CO_2(g), H₂O_(g) and CO_(g) in KJ mol^-1 are -394, -242 and -110 respectively.
A. +262 KJ mol^-1            B. -262 KJ mol^-1
C. +42 KJ mol^-1           D. -42 KJ mol-1

45. CH₃CH₂CL + KCN   →   CH₃CH₂CN + KCL
In the reaction above, the cyanide is
A. nucleophilic             B. electrophilic
C. hydrophilic               D. hydrophobic

46. The bleaching action of chlorine gas is effective due to the presence of
A. oxygen             B. hydrogen chloride
C. water               C. air

47. Which of the following pairs of substances will react further with oxygen to form a higher oxide?
A. SO₂ and NO              B. CO₂ and H₂O
C. CO and CO₂              D. NO and H₂O

48. The salt formed between citric acid and sodium hydroxide in solution will be
A. acidic                        B. neutral
C. basic                         D. amphoteric

49. On exposure to the atmosphere, a hydrated salt loses its water of crystallization to become anhydrous. This phenomenon is referred to as
A. deliquescent           B. hygroscopy
C. hydrolysis               D. efflorescence

50. Vulcanization involves the removal of
A. a double bond         B. the single bond
C. a polymer                 D. a monomer

Answers to JAMB Most Repeated Questions in Chemistry (41 – 50)

41.B        42.A       43.D       44.D      45.A
46.C        47.A       48.C       49.D      50.A

How to Pass JAMB Chemistry Questions in 2024

If Chemistry is one of your four JAMB Subject Combination, then your goal must be to get a high score in the subject.

And to pass JAMB Chemistry with a high score, you must study hard in preparation for the examination. This entails getting the Official JAMB Syllabus for Chemistry. You will also need to get one or two of the JAMB Recommended Textbooks for Chemistry and the Past Questions and Answers PDF.

Here’s one JAMB success secret you must never joke with…

Over 40% of the Chemistry questions you will see in the JAMB CBT exam hall will be repeated from the past questions.

So it’s very important that you get a good JAMB past questions and answers in Chemistry. By good past questions and answers I mean the one with a complete coverage of the past questions. It should start from the inception of JAMB exams till date. It must also have error-proof and comprehensive answers.

When you get these important JAMB preparatory tools, the next thing is to make out time for actual study. You can create a workable study time table for yourself and follow it religiously. Guided by the syllabus, read your textbooks and practice the past questions over and over.

Then pray for the best outing on your exam day.

Conclusion

Here is where we come to the end of this post on the JAMB Repeated Questions in Chemistry.

Adequate preparation is key to success. So do your best to go over these questions again and again till you master them.

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