NECO Chemistry past questions and answers

Checked by the Skolra question team · Last updated 23 October 2026

NECO Chemistry: 163 objective past questions from 4 papers between 2001 and 2009, each with the answer and an explanation. Newer NECO papers are not in our bank yet. Here are ten.

1. 1.Which of the following is a solid at room temperature?
   1. A
      Mercury
   2. B
      Sulphur
      Correct
   3. C
      Bromine
   4. D
      Chlorine
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   Answer: B

   At room temperature (about 25°C), matter can exist as solid, liquid or gas depending on how strong the forces between the particles are.

   Sulphur is a non-metal with a melting point of about 115°C, so at room temperature it exists as a yellow crystalline solid. This makes it the correct answer.

   The distractors are all substances known for NOT being solid at room temperature: mercury is unusual among metals because it is a liquid at room temperature (melting point about -39°C); bromine is the only non-metal that is liquid at room temperature; and chlorine is a gas at room temperature, existing as greenish-yellow Cl₂ molecules.

2. 2.The following acids are monobasic EXCEPT
   1. A
      Sulfuric acid
      Correct
   2. B
      Hydrochloric acid
   3. C
      Nitric acid
   4. D
      Acetic acid
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   Answer: A

   Sulfuric acid (H₂SO₄) is NOT a monobasic acid; it is a dibasic acid. Monobasic acids have only one replaceable hydrogen atom per molecule and can donate only one H⁺ ion. Hydrochloric acid (HCl), nitric acid (HNO₃), and acetic acid (CH₃COOH) are all monobasic acids with one replaceable hydrogen, while sulfuric acid has two replaceable hydrogen atoms.

3. 3.Fructose and glucose are
   1. A
      enantiomers only
   2. B
      isomers
      Correct
   3. C
      polymers
   4. D
      homologs
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   Answer: B

   Fructose and glucose both have the molecular formula C₆H₁₂O₆ but differ in their structural arrangement: glucose is an aldohexose (aldehyde group) while fructose is a ketohexose (ketone group). They are therefore structural isomers (specifically functional group isomers). Homologs differ by a CH₂ unit; polymers are large molecules built from repeating units; enantiomers are non-superimposable mirror images, which is a more specific relationship.
4. 4.A solution is prepared by dissolving 1.96g of H₂SO₄ in 250 cm³ of its solution. What is the concentration in moles per dm³?
   1. A
      0.08 mol/L
   2. B
      0.40 mol/dm³
   3. C
      0.08 mol/dm³
      Correct
   4. D
      0.16 mol/dm³
   Show answerHide answer

   Answer: C

   The concentration of H₂SO₄ solution is 0.08 mol/dm³. Using the formula: Molarity = (mass in grams / molar mass) / volume in L. Molar mass of H₂SO₄ = 98 g/mol; moles = 1.96/98 = 0.02 mol; volume = 250 cm³ = 0.25 dm³; Concentration = 0.02/0.25 = 0.08 mol/dm³. This straightforward calculation demonstrates the relationship between mass, molar mass, and molarity.

5. 5.Which statement is NOT true about the composition of starch?
   1. A
      It has the empirical formula (C₆H₁₀O₅)n
   2. B
      It contains both amylose and amylopectin fractions
   3. C
      It is made up entirely of β-glucose monomers
      Correct
   4. D
      It is a polysaccharide formed from many glucose units
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   Answer: C

   Starch is a polysaccharide built from α-glucose units, not β-glucose. β-glucose is the monomer of cellulose, another polysaccharide. Starch consists of two fractions: amylose (a linear chain) and amylopectin (a branched chain), both formed from α-glucose joined by glycosidic bonds. Its empirical formula is correctly written as (C₆H₁₀O₅)n.
6. 6.Two elements X and Y with electronic configurations 2,8,2 and 2,8,7 respectively, are likely to combine by _________bonding
   1. A
      metallic
   2. B
      coordinate (dative)
   3. C
      covalent
   4. D
      electrovalent (ionic)
      Correct
   Show answerHide answer

   Answer: D

   Element X has electronic configuration 2,8,2 — that is 12 electrons, which identifies it as magnesium (Mg), a metal with just 2 electrons in its outermost shell. Element Y has configuration 2,8,7 — 17 electrons, identifying it as chlorine (Cl), a non-metal with 7 electrons in its outermost shell, needing just 1 more to complete an octet.

7. 7.What change will occur during the electrolysis of brine using carbon electrodes?
   1. A
      sodium metal is deposited at the cathode
   2. B
      the solution becomes acidic
   3. C
      oxygen gas is produced at the anode
   4. D
      chlorine gas is produced at the anode
      Correct
   Show answerHide answer

   Answer: D

   Brine is concentrated aqueous sodium chloride. At the anode, Cl⁻ ions are preferentially discharged (over OH⁻) because of the high concentration of chloride: 2Cl⁻ → Cl₂ + 2e⁻, producing chlorine gas. At the cathode, water is reduced: 2H₂O + 2e⁻ → H₂ + 2OH⁻, giving hydrogen gas. Sodium ions are not discharged in aqueous solution; water is reduced instead. The remaining NaOH solution makes the electrolyte alkaline, not acidic.
8. 8.At s.t.p, a mole of chlorine occupies 22.4dm³. If the temperature is changed to 35°C and the pressure to 750mHg the of the new volume will be [Cl = 35.5]
   1. A
      25.6 dm³
      Correct
   2. B
      22.4 dm³
   3. C
      28.1 dm³
   4. D
      23.8 dm³
   Show answerHide answer

   Answer: A

   Using the combined gas law: V₂ = V₁ × (P₁/P₂) × (T₂/T₁). T₁ = 273 K, T₂ = 308 K, P₁ = 760 mmHg, P₂ = 750 mmHg. V₂ = 22.4 × (760/750) × (308/273) = 22.4 × 1.013 × 1.128 ≈ 25.6 dm³. The increase in temperature raises the volume while the slight decrease in pressure also increases it, both effects combine to give a volume noticeably larger than the original 22.4 dm³.
9. 9.How many atoms of chlorine are required to saturate the double bonds of a compound containing a triene?
   1. A
      6 atoms of chlorine
      Correct
   2. B
      4 atoms of chlorine
   3. C
      3 atoms of chlorine
   4. D
      2 atoms of chlorine
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   Answer: A

   A triene is a hydrocarbon that contains three carbon-to-carbon double bonds (C=C), for example hexa-1,3,5-triene.

   To saturate (remove) a double bond by addition, one molecule of chlorine, Cl₂, adds across it — that is 2 atoms of chlorine per double bond, turning C=C into C-C with a chlorine atom on each carbon.

   Since a triene has 3 double bonds, the total chlorine atoms required = 3 double bonds × 2 atoms per bond = 6 atoms of chlorine.

10. 10.The Atomic theory model which explains that electrons in an atom revolve round quantized energy levels is attributed to
    1. A
       Bohr
       Correct
    2. B
       Dalton
    3. C
       Rutherford
    4. D
       Thomson
    Show answerHide answer

    Answer: A

    Niels Bohr (1913) proposed that electrons move in fixed circular orbits called quantized energy levels around the nucleus, and can only absorb or emit energy when jumping between levels. Dalton proposed the atomic theory that all matter is made of indivisible atoms. Rutherford discovered the nucleus through the gold foil experiment. Thomson discovered the electron and proposed the plum-pudding model. Bohr’s model successfully explained the hydrogen emission spectrum.

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