Question

Which of the following is NOT always true for a combustion process taking place in a closed system?

• A. Total number of atoms is conserved
• B. Total number of molecules is conserved
• C. Total number of atoms of each element is conserved
• D. Total mass is conserved

Hint:

In chemical reactions, while atoms and mass are always conserved, the number of molecules can change depending on the reaction.

Answer 1

The Correct Option is B

Step 1: Understanding the conservation laws.
In a combustion process, the laws of conservation of mass and atoms apply. While the number of atoms of each element and the total mass remain conserved, the number of molecules can change due to chemical reactions. In combustion, molecules combine or break apart to form new compounds, so the number of molecules is not necessarily conserved. Step 2: Analysis of options.
- (A) Total number of atoms is conserved: This is true because atoms cannot be destroyed or created during a chemical reaction.
- (B) Total number of molecules is conserved: This is false, as molecules can be formed or destroyed during combustion reactions.
- (C) Total number of atoms of each element is conserved: This is true because individual atoms are not destroyed or created during a combustion reaction.
- (D) Total mass is conserved: This is true because mass is conserved in any chemical reaction, according to the law of conservation of mass.
Step 3: Final Answer.
The correct answer is (B) Total number of molecules is conserved, as the number of molecules is not always conserved in combustion processes.