What process is primarily responsible for the spreading of CuSO₄ in river water?

The spreading of CuSO₄, or copper(II) sulfate, in river water is primarily due to diffusion. Diffusion is the process through which molecules move from an area of higher concentration to an area of lower concentration, driven by the concentration gradient. When CuSO₄ is introduced into river water, it dissociates into copper ions and sulfate ions. These ions then disperse throughout the water as they move to establish a uniform concentration.

In a river context, the movement and mixing of water can enhance this process. Although convection currents could assist in mixing substances within water, diffusion is the fundamental mechanism at play here, as it occurs at the molecular level regardless of currents. Osmosis, on the other hand, specifically refers to the movement of water across a semipermeable membrane and is not applicable in this scenario. Filtration is a method used to separate particles from liquids based on size, which does not describe how CuSO₄ spreads in a solution. Therefore, diffusion is the correct answer for explaining the dispersal of CuSO₄ in river water.