List the rules for determining the osmolarity and tonicity of a solution.

Step 1: Assume that all intracellular solutes are nonpenetrating.
Step 2: Compare osmolarities before the cell is exposed to the solution.
Step 3: The Tonicity of a solution describes the volume change of a cell at equilibrium
Step 4: Determine tonicity by comparing nonpenetrating solute concentrations in the cell and the solution. The net water movement is into the compartment with a higher concentration of nonpenetrating solutes.
Step 5: Hyperosmotic solutions are always hypotonic.