Energy in Chemical Reactions
Explore the fundamental concepts of energy changes in chemical reactions, including enthalpy, entropy, Gibbs free energy, and reaction spontaneity for Grade 12 Chemistry students.
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Energy in Chemical Reactions
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Read each question carefully and provide your best answer. Show all your work for calculations.
1. Which of the following statements is true for an exothermic reaction?
The enthalpy change (ΔH) is positive.
Heat is absorbed from the surroundings.
The products have lower energy than the reactants.
The reaction feels cold to the touch.
2. What does a positive change in entropy (ΔS > 0) typically indicate?
A decrease in disorder or randomness.
An increase in disorder or randomness.
An exothermic process.
An endothermic process.
3. The energy required to break existing bonds and form new ones in a chemical reaction is known as the energy.
4. A reaction with a negative Gibbs free energy (ΔG < 0) is considered under standard conditions.
5. According to Hess's Law, the total enthalpy change for a reaction is independent of the taken.
6. All spontaneous reactions are characterized by a negative enthalpy change.
True
False
7. Increasing the temperature generally increases the spontaneity of endothermic reactions.
True
False
8. Explain the difference between an endothermic and an exothermic reaction in terms of heat flow and enthalpy change.
Match each term on the left with its definition on the right.
9. Enthalpy
a. Measure of disorder in a system
10. Entropy
b. Total heat content of a system
11. Gibbs Free Energy
c. Determines spontaneity of a reaction