Question

how does the rate of Diffusion change i) diffusion of solid in a liquid on heating ii) diffusion of a gas in a liquid on heating

Answer 1

Faster diffusion will take place if the surroundings are warmer. Increase in temperature means an increase in molecules' speed (kinetic energy). So the molecules move faster and there will be more spontaneous spreading of the material which means that diffusion occurs quicker.
It increases the rate.