Question

if human rbc with 0.9%concentration is immersed in saline 2%salinity. what are the consequences and why?

Answer 1

The red blood cells will shrink in size due to osmotic-like pressure differences until it reaches a "favorable" size.

Explanation:

Introduction
Osmosis is the physo-chemical process resulted from pressure differences.

Example of this principle is found on physiology on the celebrated Fick's law. Further, cells in general use this physical phenomenon for transporting important molecules in and out of the cells in what is named passive transport, no energy is demanded, no proteins is used for the job.