When you want to dilute a solution, what happens to the number of moles present in
the solution?

Dilution is the prosess where a solution is added more of the solvent to decrease the concentration of the solute. In dilution, the amount of solute does not change, the number of moles are the same before and after dilution.

answer: the rate of diffusion increases with increase in temperature.

increase in temperature, increases the molecular/particles speed (kinetic energy. diffusion means movement of particles through the material.

generally, the heavier the particle the more it interacts with the environment and more the temperature matters. so higher temperature results in higher diffusion.

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.