Indicate whether each of the following increases, decreases, or has no effect on the rate at whi

Indicate whether each of the following increases, decreases,...

Key Concepts

Solvent Composition and Purity

The composition and purity of a solvent can influence the dissolution process. While the chemical composition of water remains consistent regardless of its source, impurities or other additives in tap water compared to distilled water can potentially affect the interactions at the molecular level. However, these effects are usually less significant compared to factors like temperature, agitation, or solute surface area.

Temperature Effect on Solubility

Temperature plays a crucial role in the rate at which a solute dissolves in a solvent. Increasing the temperature generally speeds up the dissolution process because the molecules have more kinetic energy, which enhances their interactions. Conversely, using a lower temperature (such as water from a refrigerator) reduces molecular motion and thereby slows the dissolution rate.

Agitation and Stirring

Agitation, such as shaking or stirring, increases the dissolution rate by continuously moving the solvent around the solute. This motion helps to overcome the boundary layer that forms around the dissolving particles, allowing more solvent molecules to interact with the solute and promoting faster dissolution.

Surface Area of the Solute

The surface area of a solute is directly related to its rate of dissolution. Breaking a substance into smaller particles (like converting crystals to powdered form) increases its overall surface area available for contact with the solvent. This enhances the interaction between the solute and solvent molecules, leading to a faster rate of dissolution.

Transcript

00:01 In this question, we need to determine whether certain changes will increase or decrease the rate at which 10 grams of sugar dissolves in one liter of water.

00:14 Now, in number a, we have a situation where we're using water from the refrigerator.

00:24 So this water has a lower temperature.

00:27 So the question is now if i lower the temperature of the solvent, will this increase or decrease the rate at which the solute dissolves? now, when i decrease the temperature, i actually decrease the amount of kinetic energy available for the water molecules to move around.

00:52 So the water molecules will not be able to move around that fast and will therefore not be able to attack the solute molecules that fast.

01:05 So therefore the rate at which the solid will dissolve in the water will decrease.

01:16 So the rate there will be a decrease in the rate for this part of the question.

01:22 Now in number b, the question is whether shaking the water and sugar mixture, will this increase the rate at which the sugar dissolves in the water or will it decrease it? now, when there's a shaking, you actually increase the rate at which the solid molecules is being attacked by the solvent, which the water in this case.

01:55 So here because there's an increase in this rate of attacking, the rate of the solute dissolving in the solvent will then actually increase.

02:10 So it will dissolve at a faster rate.

02:13 In number c, the question is if we use powdered sugar instead of sugar crystals, will the rate of at which the solid dissolves in the water.

02:28 Will this increase or decrease? now, if you use powdered sugar, there's actually an increased surface area that's available for attacking.

02:40 So there's an increased surface area of the sugar that's available to be attacked by the solvent, which is water in this.

02:52 Case.

02:53 So here also there will be an increase in the rate at which the sugar dissolves in the water.

03:05 And then in number d, we have a situation where we use tap water instead of distilled water.

03:15 Right...

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