Question

What will happen to a red blood cell (rbc), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water?

Answer 1

The cell will swell up, because the water in the beaker is hypotonic relative to the cytoplasm of the red blood cell.
The red blood cell has a salt concentration that is greater than that of the pure water because of this, water will pass through the semi permeable membrane of the RBC into the cell, this will make the cell to swell up.