Final answer:
The true statement regarding combustion reactions is that they often involve the release of carbon dioxide, as they involve a substance reacting with oxygen to produce CO2, water, and heat.
Step-by-step explanation:
Among the options listed for characteristics of combustion reactions, the correct statement is that they often involve the release of carbon dioxide. Combustion reactions occur when a fuel reacts with oxygen, often resulting in the production of carbon dioxide and water, accompanied by the release of energy in the form of light and heat, indicating highly exothermic reactions. For instance, when methane (CH4) burns, the chemical reaction can be represented as CH4 + 2O2 → CO2 + 2H2O + Heat.
The combustion of hydrogen gas is a specific example that produces water vapor, described by the equation 2H2 (g) + O2 (g) → 2H2O(g). While combustions typically generate heat, it is not accurate to say that the energy release is 'light only' or that such reactions 'don't always produce heat' because heat is a fundamental byproduct of combustion processes. Additionally, combustion reactions do not entail the release of oxygen; they consume oxygen as a reactant.