Multiple Choice
Which of the following chemical or physical changes is an endothermic process?
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8. Thermochemistry
Endothermic & Exothermic Reactions
Multiple Choice
In a reaction energy diagram, which label represents the overall enthalpy change (ΔH), and how can you determine if the reaction is exothermic or endothermic?
A
ΔH is the difference between the energy of products and reactants; if products are lower in energy, the reaction is exothermic.
B
ΔH is the energy at the peak of the diagram; if the peak is higher than reactants, the reaction is exothermic.
C
ΔH is the difference between the energy of reactants and the transition state; if reactants are higher, the reaction is endothermic.
D
ΔH is the difference between the activation energy and the energy of reactants; if activation energy is higher, the reaction is endothermic.
Verified step by step guidance1
Understand that the overall enthalpy change (\$\(\Delta\) H\$) in a reaction energy diagram is defined as the difference in energy between the products and the reactants.
Identify the energy level of the reactants and the products on the diagram. \$\(\Delta\) H = E_{products} - E_{reactants}\$.
Determine the sign of \$\(\Delta\) H\$: if the products have lower energy than the reactants (\$E_{products} < E_{reactants}\$), then \$\(\Delta\) H\$ is negative, indicating an exothermic reaction where energy is released.
If the products have higher energy than the reactants (\$E_{products} > E_{reactants}\$), then \$\(\Delta\) H\$ is positive, indicating an endothermic reaction where energy is absorbed.
Note that the peak of the diagram represents the transition state and relates to activation energy, not the overall enthalpy change \$\(\Delta\) H\$.
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