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Questions and Answers
What characterizes an endothermic reaction?
What characterizes an endothermic reaction?
- The enthalpy change is negative.
- Heat is absorbed from the surroundings. (correct)
- Bond energies are always greater than bond dissociation energies.
- Heat is released to the surroundings.
Which reaction has the highest enthalpy change based on the provided examples?
Which reaction has the highest enthalpy change based on the provided examples?
- N₂(g) + O₂(g) → 2NO(g) ΔH° = +180.5 kJ (correct)
- C(s) + H₂O(g) → CO(g) + H₂(g) ΔH° = +131.4 kJ
- H₂(g) + O₂(g) → H₂O(l) ΔH° = -285.8 kJ
- H₂(g) + I₂(g) → 2HI(g) ΔH° = +53.8 kJ
What is the relationship between bond energy and bond dissociation energy?
What is the relationship between bond energy and bond dissociation energy?
- Bond energy is always greater than bond dissociation energy.
- Bond dissociation energy is related to forming bonds.
- Bond dissociation energy requires energy to break bonds. (correct)
- There is no relationship between the two.
How is the standard enthalpy change, ΔH°, defined?
How is the standard enthalpy change, ΔH°, defined?
What determines whether a reaction absorbs or releases energy?
What determines whether a reaction absorbs or releases energy?
Flashcards
Endothermic reaction
Endothermic reaction
A chemical reaction that absorbs heat from its surroundings.
Enthalpy of Reaction
Enthalpy of Reaction
The amount of heat absorbed or released during a chemical reaction.
Standard Enthalpy Change (ΔH°)
Standard Enthalpy Change (ΔH°)
The enthalpy change measured at standard conditions (25°C, 1 atm).
Bond Dissociation Energy
Bond Dissociation Energy
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Bond Energy
Bond Energy
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Study Notes
Endothermic Reactions
- Endothermic reactions absorb heat from the surroundings
- Heat is transferred from the surroundings to the system
- Examples include the decomposition of limestone, the sublimation of dry ice, and the freezing of water
Exothermic Reactions
- Exothermic reactions release heat into the surroundings
- Heat is transferred from the system to the surroundings
- Examples include the combustion of methane and the freezing of water
Enthalpy of Reaction
- Enthalpy of reaction is the amount of heat absorbed or released during a chemical reaction
- Measured at 25°C (or 298K) and one atmospheric pressure
- Negative for exothermic reactions
- Positive for endothermic reactions
Bond Energy
- Breaking bonds requires energy
- Forming bonds releases energy
- Bond dissociation energy = energy to break one mole of a particular bond
- Bond energy = energy released when forming one mole of a bond
Enthalpy Change (ΔH°)
- ΔH° = Sum of bond dissociation energies of reactants - Sum of bond energies of products
- It indicates whether the reaction absorbs or releases energy
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Description
This quiz covers key concepts in thermodynamics, focusing on endothermic and exothermic reactions, enthalpy of reaction, and bond energy. You will learn how heat transfer affects chemical processes and the implications of bond energy in thermodynamic calculations.
