What is the molal concentration of a 09 NaCl solution What i

What is the molal concentration of a 0.9% NaCl solution?

What is the osmolar concentration of a 0.9% NaCl solution?

The answers should be 0.154 molal and .307 Osm but how do you get these numbers?

Solution

1) Fw of Nacl = 23 +35.45 = 58.5

0.9% (w/v) is 0.9g/100ml = Mass concn.(g/l)/Fw

= 9/58.5= 0.154 molal

2) As we know 1M solution of a nonionizing substance such as glucose is a 1 Osmolar solution;

1M solution of NaCl = 2 Osm.

Therefore the osmolarity of the 0.9% NaCl solution is 0.15M x 2 = 0.3 Osm.