What rate of reaction can be measured in the dark by determining the amount of oxygen gas consumed in a period of time?

The rate of reaction that can be measured in the dark by determining the amount of oxygen gas consumed in a period of time is the rate of respiration.

Why?

Plants can undergo two types of reactions involving oxygen:

Photosynthesis: In this type of reaction, plants use energy from light to synthesize glucose. The chemical reaction for photosynthesis is: 6H₂O + 6CO₂ → C₆H₁₂O₆ + 6O₂, and this reaction produces oxygen gas in the presence of light, that means that to measure the rate of photsynthesis, you'll need to measure the amount of oxgen gas produced in a period of time.Respiration: In this type of reaction, plants convert the energy stored in the chemical bonds of molecules such as glucose to obtain energy. The chemical reaction for respiration is: C₆H₁₂O + 6O₂ → 6H₂O + 6CO₂, since this reaction consumes oxygen gas in the dark, that means that to measure the rate of respiration, you'll need to measure the amount of oxygen gas consumed in a period of time.

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