2018 - JAMB Chemistry Past Questions and Answers - page 2

N\(_{2(g)}\) + 3H\(_{2(g)}\) ⇔ 2NH\(_{3(g)}\) In the Haber process, the forward reaction is exothermic and the backward reaction is endothermic. If the temperature is decreased, the yield from the exothermic direction is increased i.e. the forward reaction is increased.

Formula for enthalpy change: ΔH = ΔU + Pex(ΔV)

  The enthalpy change is zero because both terms on the right are zero in free expansion of an ideal gas.

  There is no external pressure in a free expansion, so P (ex) = 0. And the internal energy change, ΔU of free expansion in a closed system is zero since no inter molecular forces have to be overcome. The temperature remains constant and no heat is absorbed or released.

Alkanones (also known as ketones) have the general formula R\(_2\)CO

Sweat consists primarily of water and electrolytes. The primary electrolytes contained in sweat are sodium and chloride. Potassium, urea, lactate, amino acids, bicarbonate and calcium are also found.

The periodic table arranges elements based on their properties, which are determined by their atomic structure. The key concept here is how elements are ordered.

• A. relative atomic number: Elements are arranged in order of increasing atomic number (number of protons). This arrangement reflects the periodic law, where properties of elements are a periodic function of their atomic numbers.
• B. atomic mass: While atomic mass generally increases across the periodic table, the modern periodic table is not strictly based on atomic mass. There are instances where elements are out of order by mass (e.g., tellurium and iodine) to maintain the correct chemical property trends.
• C. relative isotopic mass: This refers to the mass of an isotope, not the fundamental basis for arranging the entire periodic table.
• **D.

Image result for chemical composition of claywww.researchgate.net Between the five main minerals found in clay, kaolinite is the most common. Kaolinite holds the chemical composition Al2Si2O5(OH)4 and is an aluminum silicate material with a low “shrink-swell” capacity. It is a soft, white mineral but is often colored orange or red by iron oxide found in the soil

Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces.

In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. Wikipedia