Chemistry 2023 Jamb Examination

The number of neutrons is calculated as:
Neutrons = Mass number - Atomic number
= 16 - 8 = 8
Thus, this element, oxygen, has 8 neutrons.

Strong electrolytes, such as sodium chloride or hydrochloric acid, completely dissociate into ions when dissolved in water.
This complete dissociation allows them to conduct electricity very efficiently in aqueous solution.
Partial dissociation occurs in weak electrolytes, and non-polar substances do not dissociate at all.

Alkanals are aldehydes, which contain a carbonyl functional group (C=O) at the end of the carbon chain.
This carbonyl group is responsible for the characteristic chemical properties of aldehydes, including their ability to undergo oxidation reactions to form carboxylic acids.

Sulfur dioxide (SO2) reacts with water and oxygen in the atmosphere to form sulfuric acid (H2SO4), which leads to the formation of acid rain.
Acid rain can damage vegetation, aquatic life, and infrastructure by lowering the pH of soils and water bodies.

Using Boyle's Law, which states \( P_1V_1 = P_2V_2 \) at constant temperature:\[2.0 \times 4.0 = 1.0 \times V_2\]\[V_2 = \dfrac{8.0}{1.0} = 8.0\,\text{L}\]The volume of the gas doubles when the pressure is halved, keeping temperature constant.

The conversion of benzene to toluene involves replacing one hydrogen atom with a methyl group (CH3).
This occurs via an electrophilic substitution mechanism, where the benzene ring acts as a nucleophile and reacts with an electrophile (e.g., CH3+ generated from a methyl halide and AlCl3).
Since the aromaticity of benzene is preserved, it is not an addition reaction.

Water has a polar molecular structure with partial positive and negative charges, allowing it to form hydrogen bonds with a wide variety of solutes.
This polarity enables water to dissolve ionic compounds, polar molecules, and many biomolecules, making it the 'universal solvent'.
Its solvent properties are critical in biological, chemical, and environmental processes.

A colloid is a mixture where tiny particles are dispersed throughout a continuous medium but do not settle on standing.
Milk contains fat droplets dispersed in water, forming a stable colloidal suspension.
In contrast, orange juice, saltwater, and sugar solutions are true solutions where solutes are fully dissolved.

Hygroscopic substances absorb moisture from the air. Salt, sugar, and silica gel are hygroscopic and readily absorb water.
Aluminum metal, being a metallic element, does not absorb moisture from the air in the same manner and is therefore not hygroscopic.

Mass is calculated using the formula:  
Mass = Density × Volume  
Mass = 0.789 g/mL × 500 mL = 394.5 g  

Thus, 500 mL of ethanol has a mass of 394.5 g.