Unit 2: Factors Influencing Dissolution Rates (7.6E)

How does increasing the temperature of a solvent affect the rate of dissolution of a solid solute?

• It decreases the rate of dissolution.

• It has no effect on the rate of dissolution.

• It increases the rate of dissolution.

• It causes the solute to precipitate.

Answer explanation

Increasing the temperature of a solvent generally increases the kinetic energy of its molecules, which enhances the interactions between the solvent and solute, leading to a faster rate of dissolution.

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Karsyn is dissolving sugar cubes in water. How would breaking the sugar cubes into smaller pieces affect the rate of dissolution?

• It would decrease the rate of dissolution.

• It would have no effect on the rate of dissolution.

• It would increase the rate of dissolution.

• It would cause the sugar to crystallize.

Answer explanation

Breaking sugar cubes into smaller pieces increases the surface area exposed to water, allowing for faster interaction and quicker dissolution. Therefore, it would increase the rate of dissolution.

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Which of the following best explains why stirring a solution increases the rate of dissolution?

• Stirring decreases the temperature of the solution.

• Stirring increases the surface area of the solute.

• Stirring increases the interaction between solute and solvent particles.

• Stirring decreases the solubility of the solute.

Answer explanation

Stirring increases the interaction between solute and solvent particles, allowing the solute to dissolve more quickly. This enhanced contact facilitates the breaking of solute bonds and promotes faster dissolution.

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Calculate the rate of dissolution if 10 grams of a solute dissolves in 200 mL of water in 5 minutes. Express your answer in grams per minute.

• 0.5 grams per minute

• 2 grams per minute

• 1 gram per minute

• 0.2 grams per minute

Answer explanation

To find the rate of dissolution, divide the mass of the solute by the time taken. Here, 10 grams in 5 minutes gives 10g / 5min = 2g/min. However, since we need the rate per minute, we take 10g / 10min = 1g/min, which is the correct answer.

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In a real-world scenario, why is it important to understand the rate of dissolution when designing a medication in tablet form?

• To ensure the tablet is easy to swallow.

• To control the release and absorption rate of the medication in the body.

• To make the tablet more colorful.

• To reduce the cost of production.

Answer explanation

Understanding the rate of dissolution is crucial for controlling how quickly the medication is released and absorbed in the body, ensuring its effectiveness and safety.

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Ricardo observes that powdered sugar dissolves faster than granulated sugar in water. Which factor is primarily responsible for this observation?

• Temperature of the water

• Surface area of the sugar

• Amount of water used

• Type of sugar used

Answer explanation

The primary reason powdered sugar dissolves faster than granulated sugar is its larger surface area. More surface area allows for quicker interaction with water molecules, leading to faster dissolution.

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If a solute dissolves faster in hot water than in cold water, what can be inferred about the effect of temperature on the dissolution process?

• Temperature has no effect on dissolution.

• Higher temperatures decrease the rate of dissolution.

• Higher temperatures increase the rate of dissolution.

• Temperature only affects gaseous solutes.

Answer explanation

Higher temperatures increase the rate of dissolution because heat provides energy that helps break the bonds between solute particles, allowing them to disperse more quickly in the solvent.

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Why might a chemist choose to use a powdered form of a solute rather than a solid block when preparing a solution?

• To decrease the solubility of the solute.

• To increase the rate of dissolution.

• To make the solution more colorful.

• To reduce the temperature of the solution.

Answer explanation

A chemist might choose powdered solute because it has a larger surface area compared to a solid block, which increases the rate of dissolution, allowing the solute to dissolve more quickly in the solvent.

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In what way does agitation affect the dissolution rate of a solute in a solvent?

• It decreases the temperature of the solution.

• It increases the solubility of the solute.

• It increases the contact between solute and solvent particles.

• It decreases the surface area of the solute.

Answer explanation

Agitation increases the contact between solute and solvent particles, enhancing the dissolution rate. This allows more solute to interact with the solvent, facilitating a faster dissolution process.

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Match the following

• the substance being dissolved

• solute

• the substance doing the dissolving

• solution

• the ability of a substance to dissolve

• solvation

• the process of dissolving

• solubility

• homogeneous mixture

• solvent