Chemistry Regents Practice Test

In a chemical reaction, which quantity is conserved?

1. Volume only

2. Mass, Charge, and Energy

3. Pressure and Temperature

4. Energy only

The correct answer is: Mass, Charge, and Energy

In a chemical reaction, the conservation of mass, charge, and energy is a fundamental principle of chemistry. The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. This means that the total mass of the reactants must equal the total mass of the products. The conservation of charge refers to the fact that the total electrical charge in a closed system remains constant. In a reaction, even though we may have reactions that involve electron transfer, the total charge before and after the reaction will remain unchanged as the charges are balanced. Energy conservation states that energy cannot be created or destroyed, only transformed from one form to another. In chemical reactions, energy may be released or absorbed, but the total energy within the system and its surroundings remains constant. The other options refer to aspects that may change during a reaction but do not represent fundamental conservation laws. Volume, pressure, and temperature can be affected by the reaction conditions, but they are not conserved quantities in the same way that mass, charge, and energy are.