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Group 1 elements, also known as alkali metals, are not found free in nature because they are highly reactive and readily lose their single valence electron, making them eager to form chemical bonds with other elements, thus existing in compounds rather than as pure elements. They have Low ionization energy: Due to their electron configuration, group 1 elements have a low ionization energy, meaning they easily lose their outermost electron, making them highly reactive. Also, they have strong tendency to form ionic bonds: When they lose their electron, they form positively charged ions which readily attract negatively charged ions from other elements, forming stable ionic compounds.

Surface area refers to the total area of the exposed surface of a substance involved in a chemical reaction, essentially the amount of space where reactants can come into contact with each other, which significantly impacts the rate of a reaction; a larger surface area generally leads to a faster reaction rate because more reactant particles can collide and interact with each other. The efficiency of a solid catalyst to increase reaction rates depends on its surface area because a larger surface area provides more active sites for reactants to attach. This increases the rate of chemical reactions by facilitating more frequent collisions between reactant molecules and the catalyst.

Dynamic equilibrium is a state of balance between opposing forces or reactions that occurs when the forward and reverse reactions happen at the same rate. In chemistry, dynamic equilibrium occurs when a reversible reaction reaches a state where the forward and backward reactions occur at the same rate. The concentrations of the reactants and products remain constant. Dynamic equilibrium can be achieved in a closed container where none of the reactants or products can escape.

Ca\(^{2+}\) (calcium ions) are not soluble in excess NaOH (sodium hydroxide); when mixed, they form a white precipitate of calcium hydroxide (Ca(OH)\(_2\)) which does not dissolve further in excess NaOH, making it a key distinguishing factor in identifying calcium ions in solution compared to other cations like aluminum that can dissolve in excess NaOH. Mg\(^{2+}\) is not soluble in excess NaOH; when added to a solution containing Mg\(^{2+}\) ions, sodium hydroxide (NaOH) will produce a white precipitate of magnesium hydroxide (Mg(OH)\(_2\)) which is insoluble in excess NaOH. Zn\(^{2+}\) is soluble in excess NaOH, meaning that when you add a solution of sodium hydroxide (NaOH) in excess to a zinc ion Zn\(^{2+}\) solution, the initially formed white precipitate of zinc hydroxide will dissolve due to the formation of a complex ion,. Cu\(^{2+}\) (copper ion) is not soluble in excess NaOH (sodium hydroxide); when added to a solution containing Cu\(^{2+}\), NaOH will produce a blue precipitate of copper hydroxide (Cu(OH)\(_2\)) which does not dissolve in excess NaOH unless the NaOH solution is very concentrated.

SO\(_2\)(Sulphur dioxide) can react further with oxygen to form SO\(_3\) (Sulphur trioxide) a higher oxide. 2SO\(_2\) + O\(_2\) → 2SO\(_3\) NO (Nitric oxide) can also react further with oxygen to form NO\(_2\)( Nitrogen dioxide), a higher oxide. 2NO + O\(_2\) → 2NO\(_2\)

when a copper sail moistened with concentrated hydrochloric acid on a platinum wire is put on bunsen burner, the characteristics colour of the flame is green. This is due to the presence of copper ions (Cu\(^{2+}\), which emit a green light when heated.

The correct answer is A. Washing under pressure. In the industrial production of hydrogen (H₂) from natural gas, carbon dioxide (CO₂) is produced as a byproduct. To remove CO₂ from the H₂ stream, a process called pressure swing adsorption (PSA) or chemical scrubbing is used. Washing under pressure involves passing the H₂-CO₂ mixture through a solution that selectively absorbs CO₂, such as an aqueous solution of monoethanolamine (MEA) or potassium carbonate (K₂CO₃). This process is effective for removing CO₂ from the H₂ stream.