Select all of the following statements which are true about...

Select all of the following statements which are true about energy and the dissolution process. A) The enthalpy change associated with separating solvent-solvent or solute-solute interactions is always exothermic. B) Creating new solvent-solute interactions is always exothermic. C) If ?H for separating solvent-solvent and solute-solute interactions is greater than ?H for creating new solvent-solute interactions, the $\Delta H_{soln}$ will be endothermic. D) If ?H for separating solvent-solvent and solute-solute interactions is smaller than ?H for creating new solvent-solute interactions, the $\Delta H_{soln}$ will be endothermic.

Transcript

00:02 Hi there, when we're talking about energy changes during the dissolving or dissolution process, we talk about the heat of solution.

00:13 And heat of solution is the result of three separate processes that take place.

00:23 One process is for the solute, we need energy to break the intermolecular forces that hold the particles of the solute together.

00:44 The same is true for the solvent.

00:50 Energy is also needed to break apart the intermolecular forces in that substance.

00:59 So both of these are going to be endothermic because they both require energy or energy in.

01:11 And then we have the joining of the solute plus the solvent molecules.

01:18 So forces between them pulling them together or holding them together.

01:31 So we'll just say that they join and this releases energy.

01:37 So this is exothermic, whereas the first two processes were endothermic.

01:45 Okay, so the heat of solution is going to be the sum of all of these added together, the two endothermic processes and the exothermic, we're going to add those together.

02:01 So the end result, if we add all of these together, we can get a total overall endothermic process.

02:11 If the sum of the first two is greater than the third one, we could get exothermic.

02:18 If the sum of the first two is less than the exothermic portion, or we can get athermic even where they are actually the same.

02:33 So therefore there is no change in temperature overall.

02:38 Okay, so let's apply this to this question then...

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