An osmole (Osmol) is 1 mol of particles that contribute to the osmotic pressure of a solution.
For example
"CaCl"_2"(s)" → "Ca"^"2+""(aq)" + "2Cl"^"-""(aq)"CaCl2(s)→Ca2+(aq)+2Cl-(aq)
color(white)(ll)"1 mol"color(white)(mmmll)"1 mol"color(white)(mmm)"2 mol"ll1 molmmmll1 molmmm2 mol
Thus,
"1 mol CaCl"_2 ≡ "3 Osmol"1 mol CaCl2≡3 Osmol
"CaCl"_2"CaCl2 osmoles
The molar mass of "CaCl"_2CaCl2 is 110.98 g/mol.
"CaCl"_2color(white)(l) "osmoles" = "3.15" color(red)(cancel(color(black)("g"))) × (1 color(red)(cancel(color(black)("mol"))))/("110.98" color(red)(cancel(color(black)("g")))) × "3 Osmol"/(1 color(red)(cancel(color(black)("mol")))) = "0.085 15 Osmol"
"KCl" osmoles
The molar mass of "KCl" is 74.55 g/mol.
"KCl osmoles" = 0.153 color(red)(cancel(color(black)("g"))) × (1 color(red)(cancel(color(black)("mol"))))/(74.55 color(red)(cancel(color(black)("g")))) × "2 Osmol"/(1 color(red)(cancel(color(black)("mol")))) = "0.004 105 Osmol"
"K"_2"SO"_4 osmoles
The molar mass of "K"_2"SO"_4 is 174.26 g/mol.
"K"_2"SO"_4color(white)(l) "osmolarity" = "1.57" color(red)(cancel(color(black)("g"))) × (1color(red)(cancel(color(black)("mol"))))/("174.26" color(red)(cancel(color(black)("g")))) × "3 Osmol"/(1color(red)(cancel(color(black)("mol")))) = "0.027 03 Osmol"
Sucrose osmoles
The molar mass is of sucrose is 342.30 g/mol.
"Sucrose osmoles" = 0.994color(red)(cancel(color(black)("g"))) × (1color(red)(cancel(color(black)("mol"))))/(342.30 color(red)(cancel(color(black)("g")))) × "1 Osmol"/(1color(red)(cancel(color(black)("mol")))) = "0.002 904 Osmol/L"
"Total osmoles" = "(0.085 15 + 0.004 105 + 0.027 03 + 0.002 904) Osmol" = "0.119 19 Osmol"
"Osmolar concentration" = "osmoles"/"litres" = "0.119 19 Osmol"/"1 L" = "0.1192 Osmol/L"
