Question

the reaction system quick check
which quantity will always have a negative value? (1 point)
○ the change in energy in a system during an endothermic reaction
○ the total bond energy of the reactants in an endothermic reaction
○ the change in energy in a system during an exothermic reaction
○ the total bond energy of the products during an exothermic reaction

Explanation:

1. For an endothermic reaction, the system absorbs energy, so the change in energy ($\Delta E$) is positive (system gains energy). So the first option is incorrect.
2. Total bond energy of reactants in an endothermic reaction: Bond energy is a positive quantity, and in endothermic reactions, reactants' total bond energy can be less than products' (but the value itself is positive, not necessarily negative). So the second option is incorrect.
3. For an exothermic reaction, the system releases energy, so the change in energy of the system ($\Delta E$) is negative (system loses energy). This fits.
4. Total bond energy of products in an exothermic reaction: Bond energy is positive, and in exothermic reactions, products' total bond energy is less than reactants' (but the value is still positive, not negative). So the fourth option is incorrect.

Answer:

C. the change in energy in a system during an exothermic reaction