Which of the following statements is NOT true about most combustion reactions?

• A. They typically require oxygen as a reactant.
• B. They usually produce carbon dioxide and water as products.
• C. They are generally exothermic, releasing energy.
• D. They commonly occur without any change in temperature.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand what a combustion reaction is. Combustion is a chemical reaction where a substance (usually a hydrocarbon) reacts with oxygen to produce energy, typically in the form of heat and light.
2. Step 2: Recognize that most combustion reactions require oxygen as a reactant. This is because combustion is essentially a rapid oxidation process.
3. Step 3: Know the typical products of combustion of hydrocarbons, which are carbon dioxide (CO\_2) and water (H\_2O). This is due to the complete oxidation of carbon and hydrogen atoms in the fuel.
4. Step 4: Understand that combustion reactions are generally exothermic, meaning they release energy, often observed as heat and light.
5. Step 5: Analyze the statement 'They commonly occur without any change in temperature.' Since combustion releases energy, it usually causes an increase in temperature, so this statement is NOT true for most combustion reactions.