Hello everyone I have a huge request to make me aware of the mistake I make:

Namely, I have the task and substances: starch (1M), NaCl ( 0.9%), Na2SO4 ( 1M)

I am measuring with an osmometer and receive the results in turn (median values):

113,667 mOsm/kg; 272,667 mOsm/kg; 479,667 mOsm/kg

-osmometer operates -7 C ( 266 K)

- volume in ependorph of 100 ul

I calculate the theoretical values of pressure Osm with Pi = mRT (a small concentration is treated by Cn as a molar concentration):

1 starch Pi= 1 x 8.31 x 266 = 2210.46 kPa

2NaCl Pi= 2 x 8,31 x 266 = 4420,92

3 Na2SO4 Pi= 3 x 8.31 x 266 = 6631.38

Now I have to convert mOsm/kg to Pa from the values I received during the measurement ( Pi observed)

For starch:

1 mOsm - 2270 Pa ( in 273 K ) 258024,09 Pa - 273k

113,667 mOsm - x y - 266 K

x = 258024.09 Pa y = 251408.0877

for NaCl = 603083,4723 Pa and Na2SO4 =1060925,011 Pa

I calculate the isotonic factor i = Piobs/Pitorets. for NaCl and Na2SO4

NaCl- i = 0,136

Na2SO4 i=0,159

The last point is the calculation of the degree of dissociation a = ( i - 1 ) / ( n-1 ) n- l. of ions to which the substrate dissociates.

a1 = - 0,84

and there's no point in writing more, because I can't get the degree of dissociation -0.83

I think that this may be due to an erroneous conversion to Pa. I would very much like to ask for directions and possibly help in calculating the pressure

Thank you!