Chemistry 2025 Jamb Examination

Colloids are classified based on the state of the dispersed phase and the dispersion medium. Most commercial deodorants (especially sprays) consist of liquid or solid particles dispersed in a gaseous medium. This specific type of colloid is known as an aerosol. In the case of roll-ons, they might be emulsions, but in the context of general chemical classification in exams, 'deodorant' almost always refers to the aerosol spray form.

We use Faraday's laws of electrolysis. Aluminium is deposited as \(Al^{3+}\), meaning 3 moles of electrons (3F) are needed to deposit 1 mole of Aluminium.
First, find the moles of Aluminium:\[n = \frac{9}{27} = 0.3333 \text{ mol}\]Total charge required (Q):\[Q = n \times z \times F = 0.3333 \times 3 \times 96500 = 96500 \text{ C}\]Since \(Q = It\), we find time in seconds:\[t = \frac{96500}{18} \approx 5361.11 \text{ seconds}\]To convert to minutes:\[t_{\text{min}} = \frac{5361.11}{60} \approx 89.35 \text{ minutes}\]

While sulphuric acid can act as an oxidising agent or an acid, a unique and common characteristic of the *concentrated* form is its high affinity for water. It is a powerful dehydrating agent, capable of removing the elements of water (Hydrogen and Oxygen in a 2:1 ratio) from compounds like sugar or ethanol. For example, it chars sugar by leaving behind only carbon after removing the water components.

Oxidation is defined in terms of electron transfer by the mnemonic OIL RIG: Oxidation Is Loss, Reduction Is Gain. During an oxidation reaction, an atom, ion, or molecule loses electrons. Therefore, electrons are removed from the species being oxidised, resulting in an increase in its oxidation state.

1. Identify the longest chain containing the -OH group. The chain has 6 carbons, so it is a 'hexanol'.
2. Number the chain from the end closer to the -OH group. Numbering from the left puts the -OH on carbon 3. Numbering from the right puts it on carbon 4. We choose the left side: \(C_1(H_3)-C_2H(CH_3)-C_3H(OH)-C_4H_2-C_5(CH_3)_2-C_6H_3\).
3. Identify substituents: a methyl group on carbon 2 and two methyl groups on carbon 5.
4. Combine: 2,5,5-trimethylhexan-3-ol.

Anti-freeze typically consists of an alcohol with multiple hydroxyl groups (a polyol) to lower the freezing point of water through colligative properties. Ethylene glycol (ethane-1,2-diol) is the most common, but propanetriol (glycerol) is also a known non-toxic alternative. Among the options provided, propanetriol is the only polyhydric alcohol suitable for significantly lowering the freezing point while remaining stable in a radiator system.

Magnesium tetraoxosulphate(VI), commonly known as Epsom salt (\(MgSO_4 \cdot 7H_2O\)), has several medicinal and agricultural uses. In medicine, it is frequently used as a saline laxative to treat constipation because it increases the amount of water in the intestines through osmosis, stimulating bowel movements.

Permalloy is a magnetic alloy primarily composed of nickel and iron. Typically, it contains about 80% nickel and 20% iron. It is highly valued in electrical and electronic engineering for its exceptionally high magnetic permeability, which makes it useful for shielding against magnetic fields and for use in magnetic recording heads.

According to Charles's Law, the volume of a gas is directly proportional to its absolute temperature at constant pressure. When the temperature drops in a freezer, the kinetic energy of the gas molecules decreases. The molecules move more slowly and collide with the walls of the balloon with less force and frequency, exerting less pressure. To maintain pressure equilibrium with the outside air, the volume must decrease, causing the balloon to shrink.

To find the oxidation state of Nitrogen (x), we use the fact that Oxygen is typically -2 and the sum for a neutral molecule is 0:
A. \(2x + 5(-2) = 0 \implies 2x = 10 \implies x = +5\)
B. \(2x + 3(-2) = 0 \implies 2x = 6 \implies x = +3\)
C. \(2x + 4(-2) = 0 \implies 2x = 8 \implies x = +4\)
D. \(2x + 1(-2) = 0 \implies 2x = 2 \implies x = +1\)
Thus, \(N_2O_3\) (dinitrogen trioxide) has nitrogen in the +3 state.