CAST Chemistry-Segment 6-Ocean Acidification

Ocean acidification occurs when carbon dioxide (CO₂) dissolves in seawater and reacts with water to form carbonic acid (H₂CO₃), which dissociates into hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻). How would increasing the temperature of the ocean likely affect the rate of this acidification reaction?

• The rate of acidification will decrease, as higher temperatures reduce the solubility of CO₂ in water.

• The rate of acidification will remain constant, as temperature does not affect this reaction.

• The rate of acidification will increase, as higher temperatures provide more energy for the dissociation of CO₂ into H⁺ and HCO₃⁻.

• The rate of acidification will increase, but only if the concentration of dissolved CO₂ is increased.

Answer explanation

Explanation: Increasing temperature increases the kinetic energy of molecules, leading to more frequent and energetic collisions between CO₂ and H₂O molecules. This generally increases the rate at which carbonic acid dissociates into hydrogen and bicarbonate ions, contributing to increased ocean acidification.

Tags

NGSS.HS-ESS2-6

NGSS.HS-PS1-5

The increased concentration of carbon dioxide in the atmosphere leads to higher levels of dissolved CO₂ in the ocean. If the concentration of CO₂ in the ocean increases, what effect will this have on the rate of ocean acidification?

• The rate of acidification will decrease because the system will reach equilibrium more quickly.

• The rate of acidification will remain unchanged because the reaction does not depend on the concentration of CO₂.

• The rate of acidification will increase because there are more CO₂ molecules available to react with water.

• The rate of acidification will decrease because higher concentrations of CO₂ will limit the number of water molecules available for reaction.

Answer explanation

Explanation: According to the collision theory, increasing the concentration of CO₂ increases the frequency of collisions between CO₂ molecules and water molecules, which results in a faster rate of reaction, leading to greater production of H⁺ ions and increased ocean acidification.

Tags

NGSS.HS-ESS2-6

NGSS.HS-PS1-5

In coastal regions with higher temperatures, what is the likely impact on the rate of carbon dioxide dissolution in seawater and subsequent ocean acidification?

• The dissolution of CO₂ will decrease, and the rate of acidification will slow.

• The dissolution of CO₂ will increase, and the rate of acidification will accelerate due to higher kinetic energy in water molecules.

• The dissolution of CO₂ will remain constant, and the rate of acidification will not be affected.

• The dissolution of CO₂ will decrease, but the rate of acidification will increase due to increased ionization.

Answer explanation

Explanation: Higher temperatures generally lead to more rapid dissolution of gases into liquids due to increased molecular motion. In the case of ocean acidification, this means that more CO₂ can dissolve in warmer water, increasing the rate of acidification as more CO₂ molecules are available to form carbonic acid and dissociate into H⁺ and HCO₃⁻ ions.

Tags

NGSS.HS-ESS2-6

As atmospheric CO₂ levels continue to rise, the ocean absorbs more CO₂. In a lab experiment where CO₂ is bubbled through water at increasing concentrations, what effect would increasing CO₂ concentration have on the rate of hydrogen ion (H⁺) production in the solution?

• Increasing the concentration of CO₂ would decrease the rate of hydrogen ion production as the reaction reaches equilibrium.

• Increasing the concentration of CO₂ would increase the rate of hydrogen ion production because more CO₂ is available to dissociate.

• Increasing the concentration of CO₂ would have no effect, since hydrogen ions do not depend on the concentration of CO₂.

• Increasing the concentration of CO₂ would decrease the rate of hydrogen ion production by diluting the hydrogen ions in the solution.

Answer explanation

Explanation: The presence of more CO₂ molecules increases the likelihood of CO₂ reacting with water to form carbonic acid, which dissociates into hydrogen ions (H⁺). Thus, higher concentrations of CO₂ lead to more H⁺ production, contributing to increased ocean acidification.

Tags

NGSS.HS-PS1-5

Ocean acidification can have negative effects on marine organisms, especially those that rely on calcium carbonate to form shells and skeletons. If the concentration of H⁺ ions increases in the ocean, how does this affect the rate of calcium carbonate dissolution?

• The rate of calcium carbonate dissolution will decrease as the acidity of the ocean increases.

• The rate of calcium carbonate dissolution will increase as more H⁺ ions react with the carbonate ions to form bicarbonate ions.

• The rate of calcium carbonate dissolution will stay the same, as the process is independent of H⁺ ion concentration.

• The rate of calcium carbonate dissolution will increase, but only at lower temperatures.

Answer explanation

Explanation: Increased H⁺ ions in the ocean lead to a lower pH, which accelerates the dissolution of calcium carbonate. The H⁺ ions react with carbonate ions (CO₃²⁻) to form bicarbonate ions (HCO₃⁻), which results in the breakdown of calcium carbonate structures, affecting marine life that depends on calcium carbonate for shells and skeletons.

Tags

NGSS.HS-PS1-5

In a system at equilibrium, the reaction is: A(aq) + B(aq) ⇌ C(aq) + D(aq). Which of the following changes would most likely increase the amount of product C and D at equilibrium?

• Decreasing the concentration of reactant A.

• Increasing the concentration of reactant B.

• Increasing the volume of the container.

• Removing product D.

Answer explanation

Explanation: According to Le Châtelier’s Principle, adding more reactant B will shift the equilibrium toward the product side to counteract the change, increasing the formation of products C and D.

Tags

NGSS.HS-PS1-5

NGSS.HS-PS1-6

In the reaction: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) Which of the following changes would increase the amount of ammonia (NH₃) produced at equilibrium?

• Increasing the temperature.

• Decreasing the pressure.

• Increasing the concentration of hydrogen gas (H₂).

• Removing nitrogen gas (N₂) from the system.

Answer explanation

Explanation: Adding more hydrogen gas will shift the equilibrium toward the product side (NH₃) to reduce the concentration of hydrogen, leading to more ammonia formation.

Tags

NGSS.HS-PS1-5

NGSS.HS-PS1-6

In the reaction at equilibrium: CO₂(g) + H₂O(g) ⇌ H₂CO₃(aq) Which change would increase the amount of carbonic acid (H₂CO₃) produced?

• Increasing the temperature.

• Decreasing the pressure.

• Increasing the concentration of carbon dioxide (CO₂).

• Increasing the concentration of carbonic acid (H₂CO₃).

Answer explanation

Explanation: Adding more CO₂ will shift the equilibrium toward the right, increasing the formation of carbonic acid (H₂CO₃) according to Le Châtelier’s Principle.

Tags

NGSS.HS-PS1-5

For the reaction at equilibrium: PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) Which of the following actions would increase the amount of phosphorus trichloride (PCl₃) produced?

• Increasing the volume of the container.

• Removing chlorine gas (Cl₂) from the system.

• Increasing the temperature.

• Increasing the pressure.

Answer explanation

Explanation: According to Le Châtelier’s Principle, removing chlorine gas (a product) will shift the equilibrium to the right to produce more PCl₃ and Cl₂, thereby increasing the amount of PCl₃.

Tags

NGSS.HS-PS1-5

The reaction: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) is at equilibrium. Which of the following would result in an increase in ammonia (NH₃) production?

• Increasing the temperature.

• Decreasing the pressure.

• Adding a catalyst.

• Increasing the concentration of nitrogen gas (N₂).

Answer explanation

Explanation: Adding more nitrogen gas will shift the equilibrium toward the right, producing more ammonia (NH₃), as the system will try to counteract the change by consuming more N₂ and H₂ to form NH₃.

Tags

NGSS.HS-PS1-5

NGSS.HS-PS1-6