Carbon Cycle Practice

Trace carbon through combustion, respiration and photosynthesis.

SEC G3 Pure Chemistry 2027

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Which two processes add carbon dioxide to the atmosphere?

Combustion and respiration
Photosynthesis and condensation
Photosynthesis and respiration
Combustion and photosynthesis

Why can deforestation increase atmospheric carbon dioxide even if the trees are not immediately burned?

Less photosynthesis removes less $\ce{CO2}$
Less respiration removes less $\ce{CO2}$
More ozone produces $\ce{CO2}$
Nitrogen changes directly into $\ce{CO2}$

Atmospheric $\ce{CO2}$ increases while the combustion rate is unchanged. Which change could explain the increase?

A decrease in photosynthesis
An increase in photosynthesis
A decrease in respiration
More carbon dioxide being removed from air

How does decomposition return carbon to the atmosphere?

Decomposers respire as they break down organic matter, releasing CO₂
Dead organisms convert all CO₂ permanently into oxygen
Carbon atoms cease to exist when organisms die
Decomposers permanently lock every carbon atom into rock

A forest is cleared and burned. Which two changes tend to raise atmospheric carbon dioxide?

Combustion releases CO₂ and fewer trees remove it by photosynthesis
Combustion absorbs CO₂ and the bare land photosynthesises faster
Only oxygen changes because carbon cannot move between stores
Combustion stores carbon underground and tree removal increases photosynthesis

Which pair correctly identifies carbon dioxide removal into plant biomass and explains how the carbon cycle can keep atmospheric carbon dioxide approximately steady?

Respiration removes carbon dioxide; stability requires removal to balance release.
Photosynthesis removes carbon dioxide; stability requires removal to balance release.
Photosynthesis removes carbon dioxide; stability requires release to remain greater than removal.
Complete combustion removes carbon dioxide; stability requires removal to balance release.

Which statement about the carbon cycle is correct?

Respiration and combustion add carbon dioxide, photosynthesis removes it, and the balance keeps the atmospheric level fairly steady.
Photosynthesis adds carbon dioxide, and respiration removes it.
Combustion removes carbon dioxide, so burning more fuel lowers its level.
The level of carbon dioxide is fixed and cannot change.

Carbon Cycle Practice

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