Question 1
What percentage of Earth's atmosphere is made up of nitrogen gas (N₂)?No clue? Show me the answer
Correct answerCorrect!
IncorrectStep-by-step walkthrough
Choose a solution method
Method #1Direct ApproachStep 1: Recall atmospheric composition
The study notes clearly state that 78% of Earth's atmosphere is nitrogen gas (N₂).
Step 2: Check other values
Oxygen makes up about 21% of the atmosphere, so 78% must refer to nitrogen.
Step 3: Select answer
The correct answer is 78%.
Method #2Process of EliminationStep 1: Eliminate 21%
A21%21% is the approximate percentage of oxygen in the atmosphere, not nitrogen.
Step 2: Eliminate 0.04%
C0.04%0.04% is the approximate percentage of carbon dioxide (CO₂) in the atmosphere.
Step 3: Eliminate 99%
D99%99% is far too high for any single atmospheric gas and is not correct.
Step 4: Select remaining answer
The only remaining option, 78%, is the correct percentage for atmospheric nitrogen.
Question 2
Why can most living organisms NOT directly use atmospheric nitrogen gas (N₂)?No clue? Show me the answer
Correct answerCorrect!IncorrectStep-by-step walkthrough
Choose a solution method
Method #1Direct ApproachStep 1: Recall the property of N₂
The notes explain that nitrogen atoms in N₂ are held together by an incredibly strong triple bond.
Step 2: Connect to usability
Because this triple bond is so strong, plants and animals cannot break it apart to access the nitrogen atoms.
Step 3: Identify correct answer
The correct answer is that N₂ is held together by a very strong triple bond that most organisms cannot break.
Method #2Process of EliminationStep 1: Eliminate 'too heavy'
Molecular weight does not prevent a gas from entering cells; many larger molecules do enter cells.
Step 2: Eliminate 'toxic'
N₂ is not toxic — humans and animals breathe it constantly with no ill effect.
Step 3: Eliminate 'dissolves too easily'
N₂ is actually poorly soluble in water, and solubility is not the reason organisms cannot use it.
Step 4: Select correct answer
The triple bond explanation is the scientifically accurate reason, making it the correct answer.
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