Consider separate solutions of `0.500 M C_(2)H_(5)OH(aq)`,`0.100 M Mg_(3)(PO_(4))(aq)`,`0.250 M KBr(aq)`, and `0.125 M Na_(3)PO_(4)(aq)` at `25^(@)C`. Which statement is true about these solutions, assuming all salts to be strong electrolytes?

Options

A. `0.125 M Na_(3)PO_(4) (aq)` has the highest osmotic pressure
B. `0.500 M C_(H_(5))OH (aq)` has the highest osmotic pressure
C. they all have the same osmotic pressure
D. `0.100 M Mg_(3) (PO)_(2) (aq)` has the highest osmotic pressure.

Answer

3

Explanation

we have
`pi=iCRT`
For `C_(2)H_(5)OH` which neither associates nor dissociates
`pi=(1)(0.500 M)RT`
For magbesium phosphate which dissociates
`Mg_(3)(PO_(4))_(2)(aq) rarr 3 Mg^(2+)(aq)+2PO_(4)^(3-)(aq)`
`pi=(5)(0.100 M) RT`
For potassium bromide, which dissociates
`KBr(aq) rarr K^(+)(aq) pi=(2)(0.250 M)RT`
For sodium phosphate which dissociates
`Na_(3)PO_(4)(aq) rarr 3Na^(+)(aq)+PO_(4)^(3-)(aq)`
`pi=(4)(0.125 M) RT`
Thus, all have same effective molarity and are isotonic solution. They all have some osmotic pressure at the same temperature.