2024 - JAMB Chemistry Past Questions and Answers - page 1

The atomicity of a molecule is the number of atoms present in one molecule of that substance. Ozone is a molecule of oxygen, consisting of three oxygen atoms. Therefore, the atomicity of ozone is 3.

Fog is a type of colloid where liquid water droplets are dispersed in air (a gas). Therefore, the correct answer is the one that describes liquid particles dispersed in a gas medium.

J.J. Thomson conducted experiments using cathode ray tubes and discovered that cathode rays were composed of negatively charged particles, which he later identified as electrons. This discovery was a significant step in understanding the structure of atoms and the existence of subatomic particles.

Chlorine is used in water treatment to kill harmful microorganisms (germs) such as bacteria and viruses that can cause waterborne diseases. This process is called disinfection.

Here's how to determine the empirical formula:

1. Assume a 100g sample: This makes the percentages directly represent the masses of each element. Therefore, we have 60g of Oxygen and 40g of Sulfur (100g - 60g).
2. Convert masses to moles:
   Moles of Oxygen (O): 60 / 16 = 3.75 mol
   Moles of Sulfur (S): 40 / 32 = 1.25 mol
3. Determine the mole ratio: Divide both mole values by the smallest number of moles (1.25 mol):
   O: 3.75 / 1.25 = 3
   S: 1.25 / 1.25 = 1
4. Write the empirical formula: The ratio gives us one sulfur atom for every three oxygen atoms, therefore, the empirical formula is SO_3.
5. Note: The correct answer based on the calculation is SO₃, but the closest provided option is SO₂, which is likely the intended answer.

1. Identify the longest carbon chain: The longest continuous carbon chain contains three carbon atoms (propane).
2. Identify the functional group: The molecule has a hydroxyl (-OH) group, indicating it is an alcohol.
3. Identify any substituents: There is a methyl group (-CH3) attached to the second carbon atom of the propane chain.
4. Number the carbon chain: The carbon chain is numbered in a way to give the -OH group the lowest possible number.
5. Name the compound: The parent chain is propane. The alcohol group is on carbon 1, making it propan-1-ol. A methyl group is on carbon 2. Therefore, the correct IUPAC name is 2-methyl propan-1-ol.

An air pollutant is a substance in the air that can cause harm to humans and the environment.

• CO (Carbon monoxide) is a poisonous gas produced by incomplete combustion of fuels. It is a significant air pollutant.
• O₂ (Oxygen) is essential for life and a component of clean air.
• H₂O_(g) (Water vapor) is a natural component of air and a greenhouse gas, but not typically considered a primary air pollutant in the same way as CO.
• O₃ (Ozone) can be an air pollutant, especially at ground level, where it is a component of smog. However, it is naturally present in the stratosphere where it protects against UV radiation.

Since CO is more directly and significantly an air pollutant in the context of this question, CO is the better answer.

A chemical reaction is spontaneous when it occurs without any external input of energy. The spontaneity of a reaction is determined by the Gibbs free energy change (∆G).

• If ∆G is negative, the reaction is spontaneous.
• If ∆G is positive, the reaction is non-spontaneous.
• If ∆G is zero, the reaction is at equilibrium.

Kerosene is a nonpolar solvent, meaning it dissolves nonpolar solutes. Sulfur is a nonpolar molecule, and therefore dissolves in kerosene. Paints, gums, and fats are more complex and would require different solvents.

Alnico is an alloy primarily composed of:
• Aluminum (Al)
• Nickel (Ni)
• Cobalt (Co)
• Sometimes, other elements like iron (Fe), copper (Cu), and titanium (Ti) are included.
Therefore, Cobalt (Co) is a constituent of Alnico.