Unit 6 Ocean Acidification Checkpoint

About 25% - 30% of Carbon dioxide in the atmosphere is dissolved into the oceans. This Carbon dioxide (CO₂) combines with the ocean water (H₂O) to form

• calcium carbonate

  CaCO₃

• carbon monoxide

  CO

• carbonic acid 

  H₂CO₃

Answer explanation

About 25% - 30% of atmospheric CO2 dissolves in oceans, forming carbonic acid (H2CO3) when it reacts with water (H2O). This process is crucial for ocean chemistry and helps regulate pH levels.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

An example of a marine organism that needs calcium carbonate 

• coral reef

• a shark

• an octopus

Answer explanation

Coral reefs are marine organisms that require calcium carbonate to build their structures. This compound is essential for their growth and maintenance, unlike sharks and octopuses, which do not depend on it.

Tags

NGSS.MS-LS2-1

The pH scale is a range from:

• 1-7

• 0-14

• 1-5

• 1-20

Answer explanation

The pH scale measures acidity and alkalinity, ranging from 0 to 14. Values below 7 indicate acidity, while values above 7 indicate alkalinity. Therefore, the correct answer is 0-14.

A(n) ______ is a substance with a pH less than 7.

• Acid

• Alkaline

• Base

• Buffer

Answer explanation

A substance with a pH less than 7 is classified as an acid. Acids release hydrogen ions in solution, which lowers the pH, distinguishing them from alkaline substances (pH greater than 7) and bases.

pH is an indicator of

• H⁺ concentration

• acidity

• temperature

• knowledge

Answer explanation

pH measures the concentration of hydrogen ions (H+) in a solution, which directly indicates its acidity. Therefore, both H+ concentration and acidity are correct indicators of pH.

Many marine organisms that are the base of the ocean food chain make their shells from calcium and

• chloride

  Cl^-1

• carbonate

  CO₃^-2

• seawater

  NaCl + H₂O

Answer explanation

Marine organisms use calcium and carbonate (CO3^2-) to form their shells. Carbonate is essential for shell formation, while chloride and seawater do not directly contribute to shell composition.

Tags

NGSS.MS-LS2-3

Which is carbonate ion?

• HCO^-1

• H₂CO₃

• CO₃^-2

• CO₂

Answer explanation

The carbonate ion is represented as CO₃²⁻. It consists of one carbon atom and three oxygen atoms, carrying a -2 charge. The other options do not represent the carbonate ion.

Tags

NGSS.MS-PS1-1

What happens to water when it is dissolved with carbon dioxide?

• it becomes more acidic

• it becomes more basic

• it becomes healthier to drink

• it turns into coal

Answer explanation

When carbon dioxide dissolves in water, it forms carbonic acid, which increases the concentration of hydrogen ions. This process makes the water more acidic, hence the correct answer is that it becomes more acidic.

Tags

NGSS.MS-PS1-2

What does a pH of 8.1 mean?

• Neutral

• weak base

• strong base

• strong acid

Answer explanation

A pH of 8.1 indicates a solution that is slightly basic. Since it is above 7 but not significantly high, it is classified as a weak base, rather than a strong base or neutral.

An acidic solution has a

• low pH

• neutral pH

• high pH

• no pH

Answer explanation

An acidic solution is characterized by a low pH, typically below 7. This indicates a higher concentration of hydrogen ions, distinguishing it from neutral (pH 7) and basic (high pH) solutions.