Question

Blood is isotonic with.

• A. $0.16M$ $NaCl$
• B. $Conc.NaCl$
• C. $30$% $NaCl$
• D. $50$% $NaCl$

Answer 1

The correct option is A $0.16M$ $NaCl$

An isotonic solution refers to two solutions having the same osmotic pressure across a semipermeable membrane. This state allows for the free movement of water across the membrane without changing the concentration of solutes on either side.

The osmotic concentration of normal saline, $9$ grams NaCl dissolved in water to a total volume of one litre ($0.158M$), is a close approximation to the osmotic concentration of NaCl in blood. Thus, normal saline is isotonic to blood plasma. Both sodium and chloride ions cannot freely pass through the plasma membrane as opposed to urea.