Sodium thiosulphate is prepared by (a) Reducing \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) solution with \(\mathrm{H}_{2} \mathrm{~S}\) (b) Boiling \(\mathrm{Na}_{2} \mathrm{SO} 3\) solution with \(\mathrm{S}\) in alkaline medium (c) Neutralizing \(\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}\) solution with \(\mathrm{NaOH}\) (d) Boiling \(\mathrm{Na}_{2} \mathrm{SO}_{3}\) solution with \(\mathrm{S}\) in acidic medium

A chemical reaction is a process that involves the transformation of one set of chemical substances into another. It is fundamentally important in the field of chemistry, as it is through these transformations that new substances with valuable properties are created. It involves breaking and forming of bonds between atoms, accompanied by energy changes. For instance, in the preparation of sodium thiosulphate, certain reactants must interact under specific conditions to produce the desired compound. Understanding these reactions requires knowledge of reactants, products, the conditions under which the reaction occurs, and the stoichiometry - which involves balancing the equation to conserve mass and charge.

Acid-base neutralization is a type of chemical reaction where an acid and a base react to form water and a salt. This kind of reaction is integral to the preparation of many compounds, including sodium thiosulphate. When an acid, such as thiosulfuric acid (H2S2O3), reacts with a base like sodium hydroxide (NaOH), the hydrogen ions from the acid combine with the hydroxide ions from the base to form water. The remaining ions from the acid and base then form the salt, in this case, sodium thiosulphate (Na2S2O3). It's a prime example of how understanding the concept of neutralization can help in identifying the correct method of synthesizing a compound.

To determine if neutralization is the correct pathway, we must look for the presence of an acid, a base, and the formation of water along with the salt. In the provided exercise option (c), the description fits this scenario perfectly, leading to the formation of the targeted sodium thiosulphate through an acid-base reaction.

Chemistry in an alkaline medium involves reactions that occur in a basic, rather than acidic, environment. Alkaline conditions can affect the course of a reaction, including the products that are formed. In many cases, an alkaline medium can help stabilize certain reactants or intermediates, enabling reactions that might not be favorable in neutral or acidic conditions.

When preparing sodium thiosulphate, the alkaline medium plays a crucial role. The process described in option (b) requires an alkaline environment to facilitate the reaction between sodium sulfite (Na2SO3) and sulfur (S) to form sodium thiosulphate (Na2S2O3). Without the presence of a base, such as sodium hydroxide (NaOH), the wrong products might form. Through understanding how an alkaline medium can influence chemical reactivity, students can discern why certain preparation methods are employed over others, making option (b) a correct and viable method for synthesizing sodium thiosulphate.