JAMB Chemistry 2017 past questions

Checked by the Skolra question team · Last updated 15 October 2026

Ten questions from the 2017 JAMB Chemistry paper, with answers and explanations. We hold 45 questions from this paper, and the Skolra app has all of them.

JAMB Chemistry 2017 questions and answers

1.When ΔH is negative, a reaction is said to be
1. A
  Spontaneous
2. B
  Reversible
3. C
  Endothermic
4. D
  Exothermic
  Correct
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Answer: D
A negative enthalpy change, delta H, means the system loses heat to the surroundings as the reaction proceeds, which is the definition of an exothermic reaction.
An endothermic reaction has a positive delta H, and while many exothermic reactions are spontaneous or reversible, those two terms describe different properties of a reaction, not what a negative delta H itself means.
2.Aluminium hydroxide is used in the dyeing industry as a
1. A
  A mordant
  Correct
2. B
  A catalyst
3. C
  A solvent
4. D
  A bleaching agent
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Answer: A
Aluminium hydroxide is used in the dyeing industry as a mordant — it is applied to the fabric first so that it can bind to both the fibre and the dye, fixing the dye firmly to the cloth.
It plays no role as a bleaching agent, a catalyst or a solvent in this process; its job is purely to anchor the dye to the fabric.
3.In the laboratory preparation of ethyl ethanoate, the water present in the mixture is removed using a solution of
1. A
  Anhydrous calcium chloride
2. B
  Dilute hydrochloric acid
3. C
  Concentrated sulphuric(VI) acid
4. D
  Saturated sodium chloride solution (brine)
  Correct
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Answer: D
After esterification, the reaction mixture is poured into saturated sodium chloride solution. The brine lowers the solubility of the ester, so the water (together with the unreacted ethanol and ethanoic acid) stays dissolved in the aqueous layer while the ester separates out as an immiscible upper layer.
Anhydrous calcium chloride is a solid drying agent, not a solution, and concentrated sulphuric(VI) acid and dilute hydrochloric acid would react with or dilute the product rather than separate the water from it.
4.X(g) + 3Y(g) ---- 2z(g) H = +ve. if the reaction above takes place at room temperature, the G will be
1. A
  Cannot be determined
2. B
  Negative
3. C
  Positive
  Correct
4. D
  Zero
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Answer: C
Going from X(g) + 3Y(g) to 2Z(g), the number of moles of gas falls from four to two, so entropy, delta S, decreases (becomes negative) for this reaction. Since delta H is already positive, delta G = delta H - T(delta S) adds two positive quantities together (a positive delta H and a positive -T(delta S), because delta S is negative), so delta G is positive at room temperature — and in fact at any temperature.
5.CH2S(g) + O2(g) → 2Cn + SO2(g) - What is the change in the oxidation number of copper in the reaction?
1. A
  It increases from +2 to +4
2. B
  It stays the same at +2
3. C
  It increases from 0 to +1
4. D
  It decreases from +1 to 0
  Correct
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Answer: D
In the copper(I) sulphide roasted in this reaction, copper is combined with sulphur in a 2:1 ratio, so with sulphur at its typical -2 state, each copper atom carries an oxidation number of +1. In the free metal formed on the product side, copper has an oxidation number of 0.
The oxidation number therefore decreases from +1 to 0 — copper is reduced, gaining one electron per atom, so an increase in oxidation number, or copper remaining unchanged, does not match what happens in this roasting reaction.
6.Ca(OH)2(s) + 2NH4Cl(g) → CaCl2(s) + 2H2O(l) + X. In the reaction above X is
1. A
  Hydrogen chloride
2. B
  Ammonia
  Correct
3. C
  Nitrogen
4. D
  Chlorine
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Answer: B
Heating a mixture of an ammonium salt with a base is the standard laboratory method of preparing ammonia. Here, calcium hydroxide reacts with ammonium chloride to give calcium chloride, water, and ammonia gas, so X is ammonia, NH3.
Hydrogen chloride, nitrogen and chlorine do not balance the equation, and none of them is the gas actually released when an ammonium salt is heated with a base.
7.The carbon atoms on ethane are
1. A
  sp3 hybridized
  Correct
2. B
  sp hybridized
3. C
  sp2 hybridized
4. D
  Not hybridized
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Answer: A
In ethane, C2H6, each carbon atom forms four single (sigma) bonds — one to the other carbon and three to hydrogen atoms — arranged tetrahedrally. This bonding pattern corresponds to sp3 hybridization.
sp2 hybridization is found where a carbon forms a double bond (as in ethene), and sp hybridization is found where a carbon forms a triple bond (as in ethyne); ethane has neither, and its carbon atoms are certainly hybridized, not left unhybridized.
8.The constituent of air necessary in the rusting process are
1. A
  Oxygen and hydrogen
2. B
  Nitrogen and carbon(IV) oxide
3. C
  Nitrogen and oxygen
4. D
  Oxygen and water (moisture)
  Correct
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Answer: D
Rusting is an electrochemical process that requires both oxygen and moisture (water) acting together on iron; if either is absent, rusting does not occur.
Nitrogen and carbon(IV) oxide are not needed for the reaction, and while nitrogen and oxygen are both present in air, it is oxygen together with water — not nitrogen — that drives rusting.
9.Water for town supply is chlorinate to make it free from
1. A
  Its colour
2. B
  Harmful (disease-causing) bacteria
  Correct
3. C
  Suspended solid particles
4. D
  Its hardness
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Answer: B
Water meant for town supply is chlorinated mainly to disinfect it — chlorine kills harmful, disease-causing bacteria and other microorganisms, making the water safe to drink.
Chlorination is not the step used to remove hardness or suspended particles (those are dealt with by softening and filtration), and while it can affect taste slightly, its purpose is not simply to remove colour.
10.The shape of ammonia molecules is
1. A
  Tetrahedral
2. B
  Trigonal pyramidal
  Correct
3. C
  Linear
4. D
  Trigonal planar
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Answer: B
Ammonia, NH3, has three bond pairs and one lone pair on the central nitrogen atom. The lone pair pushes the three N-H bonds together, giving the molecule a trigonal pyramidal shape.
A tetrahedral shape (like methane) has no lone pair on the central atom, a trigonal planar shape has no lone pair either, and a linear shape does not apply to a central atom with four electron domains, so none of those describes ammonia.

The questions come from past JAMB, WAEC and NECO papers. We use software to help write the answer options and explanations, and every answer is checked twice before it goes on the site. How we check

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JAMB Chemistry 2017 past questions

JAMB Chemistry 2017 questions and answers

Practise all 45 questions we hold from the 2017 paper, on a timed CBT screen

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