5.1 Exothermic and endothermic reactions
1. Where is thermal energy transferred during an exothermic reaction?
Thermal energy is transferred to the surroundings.
2. What is the effect of an exothermic reaction on the temperature of the surroundings?
It leads to an increase in the temperature of the surroundings.
3. How does an endothermic reaction interact with thermal energy from its surroundings?
An endothermic reaction takes in thermal energy from the surroundings.
4. What happens to the temperature of the surroundings during an endothermic reaction?
It leads to a decrease in the temperature of the surroundings.
5. What type of diagram is used to illustrate the energy changes in exothermic and endothermic reactions?
A reaction pathway diagram.
6. What is the specific term used to describe the transfer of thermal energy during a chemical reaction?
Enthalpy change, represented by the symbol ΔH.
7. What is the mathematical sign of the enthalpy change (ΔH) for an exothermic reaction?
It is negative.
8. What is the mathematical sign of the enthalpy change (ΔH) for an endothermic reaction?
It is positive.
9. Define the term "activation energy," Ea.
Activation energy is the minimum energy that colliding particles must have to react.
10. List the four essential labels required when drawing a reaction pathway diagram.
(a) reactants, (b) products, (c) enthalpy change of the reaction (ΔH), and (d) activation energy (Ea).
11. Is the process of bond breaking classified as endothermic or exothermic?
Bond breaking is an endothermic process.
12. Is the process of bond making classified as endothermic or exothermic?
Bond making is an exothermic process.
13. How is the overall enthalpy change of a reaction explained in terms of bonds?
It is explained in terms of the energy balance between bond breaking (which requires energy) and bond making (which releases energy).