(i) → (b)

(ii) → (c)

(iii) → (d)

(iv) → (a)

EXPLANATION:

(i) ‘Philic’ means loving. Lyophilic colloids are therefore, colloidal solutions in which dispersed phase has great affinity for dispersion medium. These solutions are quite stable and are reversible in nature. Eg. sols of gum, gelatine, starch, proteins and certain polymers in organic solvents.

They have a property of protecting the lyophobic colloids by forming a layer around them when lyophilic sol is added to lyophobic sol. Thus they protect the colloid.

(ii) An emulsion is a special type of mixture made by combining two liquids that normally don't mix (immiscible).It is a colloid of two or more immiscible liquids where one liquid contains a dispersion of the other liquids. This process of turning a liquid mixture into an emulsion is called emulsification.

(iii) Charge on the colloidal particles is due to the preferential adsorption of either positive or negative ions on their surface. When FeCl₃ is added to water it will prepare a Fe(OH)₃ sol where Fe³⁺ ions are present in excess in dispersion medium and are common to lattice of sol so it get preferentially adsorbed on sol give the sol overall positive charge.

Now, when FeCl₃ is added in NaOH, the dispersion medium is excess with OH^- ion hence it gets preferentially adsorbed to the sol giving overall negative charge due to adsorption of Fe³⁺ charge.

(iv) Charge on the colloidal particles is due to the preferential adsorption of either positive or negative ions on their surface. Due to the prefferentIal adsorption of OH^-ions, a negatively charged sol is obtained when FeCl₃ is treated with NaOH.