An insoluble solid is placed in water and the system allowed to reach equilibrium. The ratio of the rate at which ions join the solution and the rate at which ions join the lattice will be:

One.

Explanation:

Hello,

In this case, the equilibrium condition is characterized by the equality of the rates at which a process happen and the contrary process happen, so its ratio is 1. For instance, a chemical reaction at equilibrium will have a contant ratio of the velocity at which the products are formed and the reactants consumed

However, for the described insoluble solid that is allowed the reach equilibrium, the ratio of the rate at which ions join the solution and the rate at which ions join the lattice will be one since it reaches an equilibrium state.

Best regards.