Match Column I with Column II

i-b; ii-c; iii-d;iv-a

The correct answer is option 4. i-b; ii-c; iii-d;iv-a

Let us go through the explanations for each matching:

i. Protective colloid ⇒ Lyophilic colloids (b)

Protective colloids are substances, often polymers, that are soluble in the dispersion medium and form a protective layer around the dispersed phase, preventing it from coagulating. This property is typical of lyophilic colloids, where the dispersed phase has a strong affinity for the dispersion medium. Thus, the protective colloid matches with lyophilic colloids.

ii. Liquid-liquid colloid ⇒ Emulsion (c)

A liquid-liquid colloid refers to a mixture where one liquid is dispersed in another liquid. When the dispersed phase is finely divided and evenly distributed throughout the continuous phase, it forms an emulsion. Examples include milk (oil dispersed in water) and vinaigrette (vinegar dispersed in oil).

iii. Positively charged colloid ⇒ \(FeCl_3\) + hot water (d)

When \(FeCl_3\) is added to hot water, it forms colloidal particles of \(Fe(OH)_3\). These particles are positively charged due to the adsorption of \(OH^-\) ions on their surfaces. Hence, \(FeCl_3\) + hot water matches with positively charged colloids.

iv. Negatively charged colloids ⇒ \(FeCl_3\) + NaOH (a)  

In the reaction between \(FeCl_3\) and \(NaOH\), \(Fe(OH)_3\) colloidal particles are formed. These particles acquire a negative charge due to the presence of excess \(OH^-\) ions in the solution. Therefore, \(FeCl_3 + NaOH\) matches with negatively charged colloids.

Each matching pairs a characteristic or type of colloid with a specific example or condition that illustrates that characteristic. This helps in understanding the properties and behaviors of colloids in different contexts.