NECO 2025/2026 Chemistry Obj & Theory Answers

CHEMISTRY OBJ

1CEDADDCCEC

(1ai)

Fermentation is the chemical breakdown of organic substances, especially sugars, by enzymes produced by microorganisms such as yeast, resulting in simpler compounds like alcohol, acids, and gases under anaerobic conditions.

OR

Fermentation is a biochemical process in which glucose (or other sugars) is broken down into ethanol and carbon dioxide by yeast or bacteria under anaerobic conditions.

(1aii)

(i) Hydrolysis of starch to glucose:

(C₆H₁₀O₅)ₙ + nH₂O ->> nC₆H₁₂O₆

(ii) Fermentation of glucose to ethanol:

C₆H₁₂O₆ ->> 2C₂H₅OH + 2CO₂

(1b)

(1ci)

Molar mass of MgCO₃ = 24 + 12 + (16 × 3) = 84 g/mol

Moles = Mass / Molar Mass = 25 / 84 = 0.299 moles

(1cii)

Methyl orange

(1ciii)

=Acidic oxides=

(i) Carbon dioxide (COâ‚‚)

(ii) Sulphur dioxide (SOâ‚‚)

(iii) Nitrogen dioxide (NOâ‚‚)

(iv) Phosphorus pentoxide (Pâ‚‚Oâ‚…)

=Neutral oxides=

(i) Nitrous oxide (Nâ‚‚O)

(ii) Carbon monoxide (CO)

(iii) Water (Hâ‚‚O)

(iv) Nitric oxide (NO)

(1civ)

(PICK ANY ONE)

(i) Hydrophobic compounds do not dissolve in water, while hydrophilic compounds dissolve easily in water.

(ii) Hydrophobic compounds repel water molecules, while hydrophilic compounds attract water molecules.

(iii) Hydrophobic compounds are usually non-polar, while hydrophilic compounds are often polar.

(iv) Hydrophobic compounds tend to cluster together in water, while hydrophilic compounds disperse evenly.

(v) Hydrophobic compounds are soluble in organic solvents, while hydrophilic compounds are soluble in aqueous solvents.

(1v)

(i) CH₃CH₂COOH ->> Propanoic acid

(ii) CH₃CH₂CH₂CH₂OH ->> Butan-1-ol

(1di)

The rate of a chemical reaction is the speed at which reactants are converted into products, usually measured by the change in concentration of a substance per unit time.

(1dii)

(PICK ANY THREE)

(i) Temperature

(ii) Concentration of reactants

(iii) Presence of a catalyst

(iv) Surface area of reactants

(v) Pressure (for gases)

(vi) Light (for photochemical reactions)

(vii) Nature of reactants

(viii) Stirring or agitation

(2)

(3)

(4)

(5)

(6)

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