2020 - JAMB Chemistry Past Questions and Answers - page 1

The electronic configuration provided is 1s² 2s² 2p⁶ 3s² 3p³. 1. **Focus on the outermost shell:** The outermost shell is the 3rd shell, which contains 3s² and 3p³. We only need to consider the 3p orbitals since the 3s orbital is completely filled and does not contain unpaired electrons. 2. **3p orbital:** The 3p subshell has three orbitals, each of which can hold a maximum of two electrons. 3. **Filling the 3p orbitals:** The 3p³ configuration means there are three electrons to be distributed in the 3p orbitals. Following Hund's rule, these electrons will singly occupy each of the three 3p orbitals before pairing up. * 3p: _↑_ _↑_ _↑_ 4. **Unpaired electrons:** From the distribution of electrons in the 3p orbitals, there are three unpaired electrons.

Fractional distillation is a separation technique used to separate miscible liquids with different boiling points. * **A. Nitrogen from liquid air:** Liquid air is a mixture of gases (primarily nitrogen and oxygen) with different boiling points. Fractional distillation can separate these components. * **B. Sodium Chloride from sea water:** Sodium chloride is a solid and can be separated from water by evaporation, not fractional distillation. * **C. Iodine from a solution of Iodine in carbon tetrachloride:** Both iodine and carbon tetrachloride are solids or miscible liquids, but in a liquid solution, they can be separated using fractional distillation. * **D. Sulphur from the solution of sulphur in carbon disulphide:** Both sulphur and carbon disulphide are solids or miscible liquids, but in a liquid solution, they can be separated using fractional distillation.

Duralumin is an alloy of aluminum, and the other primary elements in duralumin are: * **Manganese** - Adds strength and corrosion resistance. * **Magnesium** - Contributes to strength and hardness.

Polysaccharides are large carbohydrate molecules formed from many monosaccharide units joined together by glycosidic bonds. * **Starch** is a polysaccharide composed of glucose monomers. * **Dextrose** is a synonym for glucose, which is a monosaccharide. * **Mannose** is a monosaccharide. * **Glucose** is a monosaccharide.

Here's how to solve this problem: 1. **Calculate the molar mass of CH₄:** * C = 12 g/mol * H = 1 g/mol, and there are 4 H atoms, so 4 * 1 = 4 g/mol * Molar mass of CH₄ = 12 + 4 = 16 g/mol 2. **Determine the moles of CH₄:** * Given: 8 g of CH₄ * Moles = mass / molar mass = 8 g / 16 g/mol = 0.5 mol 3. **Use the given information to find the volume of 1 mole of a gas at STP:** *

The treatment: Flushed Sulfuric acid with a mild, soapy solution if the burns are not severe.

Note: Sulfuric acid feels hot when water is added to the acid, but it is better to flush the area and not leave the acid on the skin.

Warning: Don't try to neutralize the burn with acid or alkali. This could cause a chemical reaction that worsens the burn!

Charles' law states that the volume occupied by a fixed amount of gas is directly proportional to its absolute temperature, if the pressure remains constant.

The element with atomic number 17 is Chlorine which has a valency of -1.

Hence, it needs to receive an electron or lose seven electrons to obey the octet rule which refers to the tendency of atoms to prefer to have eight electrons in the valence shell. When atoms have fewer than eight electrons, they tend to react and form more stable compounds

Destructive distillation is a chemical process in which decomposition of unprocessed material is achieved by heating it to a high temperature; the term generally applies to the processing of organic material in the absence of air or in the presence of limited amounts of oxygen or other reagents, catalysts, or solvents, such as steam or phenols.

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The ash extract provides an alkali. During the soap-making process (saponification), the alkali reacts with the palm oil (a source of triglycerides) to produce soap (salts of fatty acids) and glycerol (an alkanol).