Red blood cells (RBCs) contain 0.9% NaCl and no urea in the intracellular fluid (ICF). Assuming the cell membrane of RBCs are impermeable to NaCl and permeable tour ea, predict what would happen if the extracellular fluid (ECF) contained 18.0% urea. What term describes the osmolarity of the cell? What term describes the tonicity of the solution?