Arrange the following solutions in order of decreasing freezing point: 0.10 m Na3 PO4, 0.35 m Na

Arrange the following solutions in order of decreasing...

Key Concepts

Colligative Properties

This concept explains that the effect on properties such as freezing point depends solely on the number of solute particles in the solution and not on the nature or identity of those particles. In the context of the problem, the lowering of the freezing point is determined by the total number of particles present, making it a colligative property.

Freezing Point Depression

Freezing point depression is the process where the addition of a solute to a solvent lowers the temperature at which the solvent freezes. The quantitative relationship is given by the formula ?Tf = i · Kf · m, where ?Tf is the reduction in freezing point, Kf is the cryoscopic constant of the solvent, m is the molality of the solution, and i is the van’t Hoff factor.

van’t Hoff Factor

The van’t Hoff factor (i) represents the number of particles into which a solute dissociates in solution. For electrolytes that dissociate, i multiplies the molality to give the effective concentration of particles, while non-electrolytes do not dissociate and have an i value of 1. This factor is crucial in calculating the magnitude of freezing point depression in each solution.

Electrolyte and Non-electrolyte Behavior

Understanding the distinction between electrolytes, which dissociate into ions in solution, and non-electrolytes, which remain as intact molecules, is key. In problems involving freezing point depression, electrolytes produce more particles per unit of solute than non-electrolytes, thereby causing a greater depression of the freezing point.

Molality

Molality (m) is defined as the number of moles of solute per kilogram of solvent and is used in the freezing point depression formula. It is a concentration unit that does not change with temperature, making it reliable for calculations involving thermal changes such as freezing point depression.

Transcript

00:01 Okay, so we have several solutions and we have to rank then in decreasing freezing point.

00:11 The important thing about this question is to consider the dissociation pattern in this substance.

00:22 Okay, so the freezing point change follows this formula.

00:30 It's a constant, okay, that depends on the substance.

00:34 It depends on the solvent.

00:37 There's a negative sign just to remind you that this is going down.

00:42 So the freezing point goes down as you increase the concentration of the particles.

00:47 Then you have the molality of the solution.

00:50 And there's one extra piece.

00:53 Okay, action.

00:54 We can represent as an eye.

00:57 That eye is used to take in account the dissociation.

01:08 What that means? well, it really, the collagative properties, they depend on the number of particles in the solution, not really the number of molecules just started.

01:21 Because molecules, you may have a big molecule, but when you put that in solution, that breaks into smaller particles.

01:31 Okay.

01:32 So the number of these smaller particles is what matters.

01:36 So this i exist to take in an account.

01:40 Dissociation.

01:42 So for example, in this case i would be three, right? because this big molecule here or crystal or whatever is that, it broke into three pieces.

01:57 So for each species, we have to consider whether or not that would be dissociation.

02:06 So first let's look at sugar.

02:11 So let's see, let's see.

02:19 C6h226.

02:21 Actually sugar is a molecule and there's no significant dissociation when you put that in water.

02:30 So it's solid, it's right, a complete reaction.

02:34 When it goes through this solution, it won't change the structure, it will just be salvated by water.

02:46 So i would be just one because one particle became one particle.

02:55 The tricky one among the list in the question is c -h -3 -c -o -o.

03:06 Because this one actually establishes an equilibrium.

03:13 So once it's dissolved in water, it can disassociate...