An isotonic solution contains 0.90% NaCl mass to volume....

An isotonic solution contains 0.90$\%$ NaCl mass to volume. Calculate the percent mass to volume for isotonic solutions containing each solute at $25^{\circ} \mathrm{C}$ . Assume a van't Hoff factor of 1.9 for all ionic solutes.$a. KCl \quad$ b. NaBr $\quad$ c. glucose $\left(\mathrm{C}_{6} \mathrm{H}_{2} \mathrm{O}_{6}\right)$

Key Concepts

Isotonic Solutions

An isotonic solution is one that has the same osmotic pressure as another solution, typically the bodily fluids, which prevents net movement of water across semipermeable membranes. In calculations, ensuring isotonicity often means matching the effective concentration of solute particles that contribute to osmotic pressure.

Percent Mass to Volume Concentration

Percent mass to volume (% m/v) is a concentration metric that expresses the grams of solute present in 100 mL of solution. It is commonly used in preparing medical solutions and other laboratory solutions to precisely control the solute concentration.

Van't Hoff Factor

The van't Hoff factor (i) represents the number of particles into which a solute dissociates in solution. In osmotic pressure calculations, it adjusts the effective particle concentration, making it crucial for comparing the osmotic effects of different solutes even if their mass concentrations are the same.

Molar Mass

Molar mass is the mass of one mole of a substance, usually given in grams per mole. It is essential in converting a percent mass to volume concentration into moles per liter, which is a step required to calculate the number of solute particles contributing to osmotic pressure.

Transcript

00:01 Okay, so let's get started on this question.

00:03 So the first thing we need to realize is that we're dealing with an isotonic solution.

00:07 So that means that the osmotic pressure of our sodium chloride solution is going to be the same as that in the surrounding environment.

00:14 Basically, the question is asking us, what percent mass to volume for these other solutes when dissolved? we'll have the same osmotic pressure as a sodium chloride solution.

00:23 So we can just start by equating the osmotic pressure of our sodium chloride solution to that of our other solutes.

00:30 Which we're just going to denote as sol.

00:32 And since we know the equation for osmonic pressure, we can just plug in those values.

00:37 So we have our vent hot factor for sodium chloride multiplied by the molar concentration of sodium chloride at times the gas constant and temperature.

00:47 And then we can do the same thing for our solutes on this side.

00:51 So it's nice and straightforward.

00:55 Now the first thing we need to notice is that the gas constant and temperature are the same on both sides of the equation, so they cancel each other out.

01:02 The next thing is that our molar concentration is in moles, whereas in the question we're given a percent mass to volume.

01:09 So convert that mass to moles, so we can use it in this equation.

01:13 We need to just divide by the molar mass.

01:15 So let me write that out, so it's a little bit more straightforward to follow.

01:19 So instead of this term, we'll write the percent mass to volume of sodium chloride, divided by the molar mass of sodium chloride.

01:29 And then we'll do the same thing for the solutes.

01:33 So in this case, we'll have the percent mass to volume of our solutes divided by the molar mass of our solutes.

01:42 So this is nice because it allows us to now solve for what the question is asking us to solve for, the percent mass to volume of solutes.

01:51 And you can rearrange this however you want to solve for that.

01:54 I'm just going to show it like this, though...

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