2024 - JAMB Chemistry Past Questions and Answers - page 7

The petroleum industry involves the extraction, refining, and processing of crude oil.

Cracking: Breaks down large hydrocarbon molecules into smaller ones, a key process in refining petroleum.

Polymerization: Combines small molecules (monomers) into larger ones (polymers), another process used in petroleum refining to create products like plastics.

Fermentation: A biochemical process that uses microorganisms to convert carbohydrates into simpler substances like alcohol and carbon dioxide. It is not a process used in the petroleum industry.

Saponification: The process of making soap by reacting a fat or oil with an alkali. While fats and oils have some relationship to hydrocarbons, saponification is not used in the petroleum industry.

Permanent hardness in water is caused by the presence of dissolved minerals, specifically the sulfates, chlorides, and nitrates of calcium (Ca²⁺) and magnesium (Mg²⁺). These ions do not precipitate out upon boiling, hence the term 'permanent' hardness.

A normal salt is formed when a strong acid reacts with a strong base. In this reaction, the acid and base neutralize each other completely, and the resulting salt does not have any excess hydrogen or hydroxide ions, hence it is neutral.

The Millon's test is a chemical test used to detect the presence of proteins. When Millon's reagent (mercury(II) ions in nitric acid) is added to a solution containing protein, a white precipitate forms. Upon heating, or sometimes with time, the precipitate turns brick red. This color change is due to the nitration of tyrosine residues in the protein.

Van der Waals forces are weak intermolecular forces that occur between molecules. These forces arise from temporary fluctuations in electron distribution, creating temporary dipoles.

Here's how to determine the correct IUPAC name for K₄Fe(CN)₆:

1. Identify the cation and anion: The compound is an ionic compound. The cation is potassium (K⁺) and the anion is the complex ion [Fe(CN)₆]⁴⁻.

2. Name the ligands: The ligand is cyanide (CN⁻). Since there are six cyanide ligands, the prefix 'hexa' is used.

3. Name the central metal: The central metal is iron (Fe).

4. Determine the oxidation state of the metal: Potassium (K) has a +1 charge. Four potassium ions contribute +4. Six cyanide ligands contribute -6. Let x be the oxidation state of iron: +4 + x - 6 = 0 → x = +2.

5. Combine the names: The IUPAC name is potassium hexacyanoferrate(II). The Roman numeral (II) indicates the oxidation state of iron.

An acid anhydride is a non-metal oxide that reacts with water to form an acid. We are looking for an element (X) that combines with oxygen to form an oxide (XO₂) which, when reacting with water, produces an acid.

Phosphorus forms P₂O₅ → H₃PO₄, Chlorine forms Cl₂O₇ → HClO₄, Fluorine forms F₂O (does not readily form XO₂ acids), Sulphur forms SO₂ → H₂SO₃ and SO₃ → H₂SO₄. Therefore, Sulphur is the best fit.

Functional group isomers are compounds that have the same molecular formula but different functional groups.

• S (ROR'): Ethers
• T (RCOOH): Carboxylic acids
• U (RCOR'): Ketones
• V (ROH): Alcohols
• W (RCOOR'): Esters

T and U (carboxylic acids and ketones) can form functional group isomers, e.g., propanoic acid and propanone.

To determine X, we apply conservation of mass and atomic numbers:

Mass number: 14 (N) + A(X) = 14 (C) + 1 (P) → A(X) = 1

Atomic number: 7 (N) + Z(X) = 6 (C) + 1 (P) → Z(X) = 0

A particle with mass number 1 and atomic number 0 is a neutron. Therefore, X is a neutron.

The Contact Process is used for producing sulfuric acid. The critical step involves the catalytic oxidation of sulfur dioxide (SO₂) to sulfur trioxide (SO₃). The catalyst used is vanadium(V) oxide (V₂O₅).