The Nitrogen Cyle

What percentage of the atmosphere is made up of atmospheric nitrogen (N₂)?

• 21%

• 78%

• 50%

• 10%

Why is atmospheric nitrogen (N₂) unusable by most organisms?

• It is too reactive.

• It is unusable

• It is too dense.

• It is too light.

Why is nitrogen considered an essential element for living organisms?

• It is used for photosynthesis.

• It is vital for proteins, DNA, and other biological molecules.

• It provides energy.

• It is a primary component of carbohydrates.

What does ammonia (NH3) spontaneously become during nitrogen fixation?

• Nitrite (NO2-)

• Nitrate (NO3-)

• Ammonium (NH4+)

• Nitrogen gas (N2)

What are the primary reactants in the industrial fixation process to form ammonia?

• Oxygen and hydrogen

• Nitrogen and oxygen

• Nitrogen and hydrogen

• Hydrogen and carbon dioxide

What is a common use of ammonia produced through industrial fixation?

• As a fuel

• As a fertilizer

• As a solvent

• As a metal cleaner

What is biological nitrogen fixation carried out by?

• Certain bacteria

• Certain fungi

• Certain viruses

• Certain algae

What compound is produced during the process of biological nitrogen fixation?

• Methane (CH₄)

• Ammonia (NH₃)

• Carbon dioxide (CO₂)

• Oxygen (O₂)

What is the process called where ammonium is converted by bacteria into nitrites and then nitrates?

• Denitrification

• Nitrification

• Ammonification

• Nitrogen fixation

What is the process called where some nitrates are converted back into nitrogen gas?

• Nitrification

• Denitrification

• Ammonification

• Assimilation