GED Science Practice

What is a heavy, odorless, colorless gas formed during respiration and by the decomposition of organic substances?

1. Carbon Dioxide

2. Carbon Monoxide

3. Carcinoma

4. Catalyst

The correct answer is: Carbon Monoxide

The correct answer is carbon dioxide, which is a heavy, odorless, colorless gas produced during the process of respiration in living organisms, including humans. During respiration, cells convert glucose and oxygen into energy, releasing carbon dioxide as a byproduct. This gas is also generated during the decomposition of organic substances, as microorganisms break down the material and release carbon dioxide in the process. Carbon dioxide plays a crucial role in the Earth's atmosphere, serving as a greenhouse gas and being critical for photosynthesis in plants. Unlike carbon monoxide, which is a harmful gas produced by incomplete combustion of carbon-containing substances, carbon dioxide is a natural and essential component of the respiratory cycle. Other options, like carcinoma and catalyst, are unrelated to the decomposition process or respiration. Carcinoma refers to a type of cancer, which is not a gas, while a catalyst is a substance that speeds up a chemical reaction without undergoing permanent change itself, not a gas produced during respiration or decay.