Question

Using the equation for osmotic pressure as a guide, theoretically rank the solutions from best to worst in terms of ability to hydrate chickpeas.

1 M NaCl

Pure Water

2M KCl

1 M Na₂SO₄

1 M KCl

Answer 1

The equation for osmotic pressure is

osmotic pressure = i x CRT

where i = van't Hoff factor , C = molar concentration , R = gas constant, T = absolute temperature

RT being same for all, let us compare the value of iC

1M NaCl iC = 2 x1= 2

2MKCl = 2x2 = 4

1MNa2SO4 = 3x1 =3

1MKCl = 2x1 = 2 Thus 2M KCl will have the highest osmotic pressure .

soaking of seeds is the process of osmosis which occurs from water to seed. Thus the more concentrated the solution, less is the soaking of seeds.

Thus hydration of chickpeas occurs in pure water most and in 2M Hcl least.

Thus the ranking is

pure water > 1MNaCl=1M KCcl > 1M Na2SO4 > 2MKCl