What is the osmolarity of the following solutions?
a. 0....

Question

What is the osmolarity of the following solutions?

a. 0.35 M KBr

b. 0.15 M glucose + 0.05 M K₂SO₄

Accepted Answer

Welcome back, everyone determine the osmolarity of a solution containing 0.4 50 molar glycerol and 0.15 molar sodium sulfate. So, in order to determine the osmolarity of the solution, we're going to need to take the sum between the osmolarity of Glycerol, which is C three H 803 added to the osmolarity of sodium sulfate N A two. So four, meaning we need to find the individual osmolarity of these substances first. So starting with finding the osmolarity of Glycerol. We're going to find that by recognizing that Glycerol consists of all nonmetal atoms, carbon hydrogen and oxygen and being all nonmetals, this is going to be a covalent compound also known as molecular compound. And so therefore, it's going to be a non electrolyte and will not dissociate into ions. So it's going to remain as an undissolved molecule in the solution. And let's recall that for molecular substances, the osmolarity of a molecular compound is equal to its polarity. And because we are given the molar concentration of 0.4 50 molar glycerol, then therefore, its osmolarity is going to be equal to that same value 0.4 50 the units for osmolarity recall are osmoles per liter. So now with our osmolarity of glycerol, figured out, let's now determine the osmolarity of sodium sulfate. So let's recognize that sodium sulfate consists of the metallic atom, sodium and nonmetallic atom sulfur and oxygen. This is then therefore an ionic compound. So it's therefore considered a salt. And if we recall our solubility rules for sodium salts, which this would be a sodium salt, this is going to then therefore be soluble. So we would label it as aqueous and it's going to dissolve fully into its corresponding ions where we got two moles of our sodium plus one Calion as a product along with one mole of our sulfate. So +42 minus anion as a second product. And note that it is two moles of sodium plus one count on forms given by the subscript of two in the chemical formula of sodium sulfate. So now we can understand that sodium sulfate yields three moles of ions total where we've got two moles of our sodium ion generated as a product along with one mole of our sulfate minus two anion generated as a second product. So that is three moles of ions total. And in order to determine the osmolarity of sodium sulfate, we would recall that this would be found by taking the polarity of sodium sulfate multiplied by the moles of dissolve ions per mole of sodium sulfate. And this is because as we stated, osmolarity is in units of osmoles per liter. And if we recall molar, in terms of moles per liter, we would be able to cancel out moles leaving us with moles of ions per liter. And recall that moles of ions per liter is equivalent to osmos per liter. So that's just something we recall from our notes in our textbooks. And let's go ahead and calculate this osmolarity for sodium sulfate. So, incorporating its molar concentration given as 0.15 molar, we will interpret that as 0.15 moles of sodium sulfate per liter of solution. And now we will multiply where we will interpret from our full dissociation of sodium sulfate that we've got three moles of ions total in the numerator for one mole of sodium sulfate in the denominator dissolved. So notice that we can cancel out our units of moles leaving us with moles of ions per liter. And this is going to simplify to a value of 0.45 moles of ions per liter, which as we stated, moles of ions per liter are equivalent to osmoles per liter. So we can interpret this as the osmolarity of 0.45 osmoles per liter for sodium sulfate. So now with our two determined osmolarity, we can move forward to calculate the total osmolarity of the solution, which as we stated above is found from the sum of the osmolarity of glycerol to the sum of the osmolarity of sodium sulfate. So applying that below, we will plug in the osmolarity of glycerol, which we determined to be 0.450 osmoles per liter, which is added to the osmolarity of sodium sulfate, which we determined above to be 0.45 osmoles per liter. So from the sum, we'll get the osmolarity of the solution as a whole equal to 0.90 osmoles per liter. And that is our answer rounded to the correct number of significant figures being two significant figures total. Though, again, the osmolarity of the solution is 0.90 osmos per liter. As our final answer, I hope this made sense and let us know if you have any questions.

What is the osmolarity of the following solutions?
a. 0.35 M KBr
b. 0.15 M glucose + 0.05 M K₂SO₄

Key Concepts

Osmolarity

Ionic Dissociation

Non-Electrolytes vs. Electrolytes

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