Q1: With increase in temperature, the leaching rate increases due to

ANS:C - both (a) and (b)

With an increase in temperature, the leaching rate increases due to both (a) and (b): Explanation: (a) Decreased liquid viscosity:

• As temperature increases, the viscosity of the leaching solution typically decreases. Viscosity is a measure of a fluid's resistance to flow.
• Lower viscosity facilitates faster movement and mixing of the leaching solution with the solid material being leached.
• Reduced viscosity leads to improved mass transfer kinetics, allowing the leaching solution to more efficiently access the surface of the solid particles and dissolve the desired components.
• Therefore, decreased liquid viscosity at higher temperatures promotes enhanced fluid flow and contact between the leaching solution and the solid, contributing to higher leaching rates.

(b) Increased diffusivity:

• Temperature has a significant effect on the diffusivity of solute molecules in the leaching solution.
• Higher temperatures increase the kinetic energy of molecules, resulting in faster diffusion rates.
• This enhanced diffusivity accelerates the transport of solute molecules from the solid phase to the bulk of the leaching solution and vice versa.
• As a result, at elevated temperatures, solute molecules can more rapidly migrate through the solution to and from the solid surface, promoting faster dissolution and higher leaching rates.
• Therefore, increased diffusivity at higher temperatures facilitates more efficient mass transfer during the leaching process, leading to enhanced leaching rates.

In summary, both decreased liquid viscosity and increased diffusivity contribute to the increase in leaching rate with temperature. Lower viscosity promotes better fluid flow and contact, while higher diffusivity facilitates faster solute transport, ultimately leading to higher leaching efficiency.