How do you calculate the osmolarity of a #6.0 * 10^-2# M NaCl solution?

Question

Peyton Adams · Accepted Answer

#"0.12 osmolar"#

As you know, osmolarity tells you how many particles of a solute you get per liter of solution.

Osmolarity is expressed in number of osmoles, or solute particles, per liters of solution.

When dealing with soluble ionic compounds, you have to keep track of how many ions you get per formula unit. Sodium chloride, #"NaCl"#, will dissociate completely in aqueous solution to produce sodium cations, #"Na"^(+)#, and chloride anions, #"Cl"^(-)#

#"NaCl"_text((aq]) -> "Na"_text((aq])^(+) + "Cl"_text((aq])^(-)#

As you can see, each mole of sodium chloride will produce two osmoles in solution.

This means that you will have

#6.0 * 10^(-2)color(red)(cancel(color(black)("moles")))/"L" * "2 Osmoles"/(1color(red)(cancel(color(black)("mole")))) = 12 * 10^(-2)"Osmoles/L"#

Noah Aldrich · Answer

undefined To calculate the osmolarity of a solution, you need to consider the number of particles present in the solution. For NaCl, it dissociates into two ions: Na⁺ and Cl⁻. Therefore, each molecule of NaCl contributes two particles to the solution. To find the osmolarity, multiply the molarity of NaCl by the number of particles it produces when it dissociates. In this case, 6.0 * 10^-2 M NaCl solution has an osmolarity of 2 * 6.0 * 10^-2 = 1.2 * 10^-1 osmoles/L, or 0.12 osmoles/L.