In atmospheric chemistry, the hydroxyl radical (\text{OH}) is the primary oxidant clearing… — SAT

In atmospheric chemistry, the hydroxyl radical ( $\text{OH}$ ) is the primary oxidant clearing pollutants from the lower atmosphere. Scientists long assumed that dense forest canopies, which emit high levels of volatile organic compounds (VOCs) like isoprene, would rapidly deplete local $\text{OH}$ concentrations. However, recent measurements in pristine tropical forests revealed stable $\text{OH}$ levels despite intense VOC emissions. To explain this, chemists simulated canopy conditions and found that the oxidation of isoprene by $\text{OH}$ , under the low-nitrogen-oxide conditions typical of remote forests, initiates a series of isomerization steps that regenerate $\text{OH}$ molecules. This suggests that ______

Which choice most logically completes the text?

the chemical consumption of $\text{OH}$ in these environments is offset by reactions that replenish the radical.Cevap
B
dense forest canopies are the primary source of all atmospheric oxidants in the lower atmosphere.
C
isoprene is more effective at clearing pollutants from the lower atmosphere than the hydroxyl radical is.
D
tropical rainforests will eventually experience a rapid decline in self-cleaning capacity as global VOC emissions continue to rise.

Cevap

the chemical consumption of

\text{OH}

in these environments is offset by reactions that replenish the radical.

The text states that scientists expected VOCs like isoprene to deplete local

\text{OH}

levels, but measurements showed stable

\text{OH}

levels. Chemists discovered that under low-nitrogen-oxide conditions, the oxidation of isoprene by

\text{OH}

actually initiates steps that regenerate

\text{OH}

molecules. This directly supports the inference that the chemical consumption of

\text{OH}

is offset by reactions that replenish the radical, keeping the levels stable.

Adım Adım Çözüm

Identify the primary function of the hydroxyl radical (

\text{OH}

) and the initial assumption about dense forest canopies.

The text states that

\text{OH}

is the primary oxidant clearing pollutants, and scientists assumed that high concentrations of volatile organic compounds (VOCs) like isoprene emitted by forest canopies would rapidly deplete local

\text{OH}

levels.

Establishing the initial premise helps frame the conflict between expected depletion and observed stability.

Analyze the conflicting evidence and the mechanism discovered by chemists.

Recent measurements show that canopy

\text{OH}

levels remain stable. The chemical simulation reveals that under the low-nitrogen-oxide conditions typical of remote forests, the oxidation of isoprene by

\text{OH}

initiates a series of isomerization steps that regenerate

\text{OH}

molecules.

This step identifies the mechanism responsible for maintaining stable

\text{OH}

concentrations despite the emissions that consume them.

Draw a logical conclusion that connects the chemical consumption to the regeneration mechanism.

Since the reaction that consumes

\text{OH}

also triggers steps that regenerate it, the consumption is balanced or offset by replenishment, explaining why

\text{OH}

levels remain stable.

Synthesizing these points yields the logical inference that completes the passage.

Anahtar Kavram

Logical Inferences

Soru

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