ANS:A - form a water repelling film on the mineral surface.

The role of a "collector" in froth flotation is to form a water-repelling film on the mineral surface. Froth flotation is a process used for selectively separating hydrophobic materials from hydrophilic ones. In this process, finely ground ore particles are suspended in water and aerated. Air bubbles are introduced into the mixture, and the hydrophobic particles adhere to the air bubbles, forming a froth on the surface of the flotation cell. The hydrophilic particles remain in the water phase. Collectors are surface-active agents or surfactants that are added to the flotation pulp to selectively enhance the hydrophobicity of the desired mineral particles. They adsorb onto the surface of the mineral particles, forming a water-repelling film or coating. This coating allows the hydrophobic particles to attach to the air bubbles and become entrained in the froth, while the hydrophilic particles remain in the water phase and are eventually discharged as tailings. In summary, collectors play a crucial role in froth flotation by selectively coating the desired mineral particles with a water-repelling film, thereby facilitating their attachment to the air bubbles and their recovery in the froth phase.