The state's landlord-tenant laws protect people living in dwellings owned or leased by others. A person need not be listed on a formal lease to gain protection under these laws, but may gain protection by establishing residence in a place.
The mole is useful in chemistry because it is defined such that the mass of Avogadro's number of particles (atoms or molecules) of a substance (the molar mass) is equal to the sum of the numerical values of the atomic masses of its constituent elements.
You need to know the true formula weight (molar mass) in order to measure out the mass needed togive a certain number of moles. The chemical importance of the water of hydration is minimal since it can bedriven off by heat or simply dissolve away if the salt is dissolved in water.