Question

chemical a and chemical b react in an exothermic reaction. what can be known about what will happen when chemical a and chemical b are mixed together?
the old substance will need more energy to break its chemical bonds than the new substance will release.
more energy will be released from the old substance than the new substance will release to form its chemical bonds.
the color will change as a result of the reaction.
the substance will bubble as a result of the reaction.

Explanation:

1. For an exothermic reaction, the energy released when new bonds form is greater than the energy absorbed to break old bonds. So, the energy from breaking old substances (bonds) is less than the energy released by new substances (bond formation), but rephrased: more energy is released overall (since it's exothermic). Let's analyze each option:

• Option 1: In exothermic, energy to break old bonds is less than energy released by new bonds. So this is wrong.
• Option 2: In exothermic reactions, the energy released when forming new bonds (of new substance) is more than the energy needed to break old bonds (of old substances). But the option says "More energy will be released from the old substance (breaking bonds? Wait, no—wait, maybe phrased as: the energy released (from the reaction, which is net exothermic) means that the energy released when new bonds form is more than energy absorbed to break old bonds. So the option's wording: "More energy will be released from the old substance (maybe meaning the energy released during bond breaking? No, wait, bond breaking absorbs energy. Wait, maybe the option is saying that the energy released (net) is because the energy from breaking old bonds (absorbed) is less than energy from forming new bonds (released). So the option's statement: "More energy will be released from the old substance than the new substance will release to form its chemical bonds"—wait, no, maybe I misread. Wait, exothermic: total energy released (from new bonds) > total energy absorbed (to break old bonds). So the net is release. So the option 2: "More energy will be released from the old substance (maybe the energy that was in the old substance, but when reacting, the energy released when new bonds form is more than the energy needed to break old bonds. So the option is saying that the energy released (from the reaction) is because the energy from breaking old bonds (absorbed) is less than energy from forming new bonds (released). So the option's wording: "More energy will be released from the old substance than the new substance will release to form its chemical bonds"—no, maybe the option is phrased as: the energy released (net) is positive, so the energy released when new bonds form is more than the energy absorbed to break old bonds. So the option 2 is correct? Wait, let's re-express:
• In exothermic reaction: \( E_{\text{break old bonds}} < E_{\text{form new bonds}} \). So the net energy released is \( E_{\text{form new bonds}} - E_{\text{break old bonds}} > 0 \). So the option 2: "More energy will be released from the old substance than the new substance will release to form its chemical bonds"—wait, maybe the option is saying that the energy released (from the reaction) is such that the energy from the old substance (when bonds break, but bond breaking absorbs energy) no—maybe the option is misphrased, but among the options, option 2 is the only one related to energy in exothermic.
• Option 3: Color change is not a universal sign of exothermic reactions. Many exothermic reactions don't change color.
• Option 4: Bubbling (gas production) is not a universal sign of exothermic reactions. Many exothermic reactions don't produce gas.

So the correct option is the second one.

Answer:

B. More energy will be released from the old substance than the new substance will release to form its chemical bonds.