교과서 질문
Calculate ΔE and determine whether the process is endothermic or exothermic for the following cases: (b) A system releases 66.1 kJ of heat to its surroundings while the surroundings do 44.0 kJ of work on the system.
8. Thermochemistry
Endothermic & Exothermic Reactions
Multiple Choice
Two compounds were dissolved in water and mixed together. A precipitate formed, and the test tube got very warm. Based on this information, which of these statements is true?
A
This process is endothermic and absorbs heat from the surroundings.
B
The precipitate must be an element.
C
The temperature increase indicates that the reaction is endothermic.
D
This process is exothermic and has a negative value for heat.
검증된 단계별 안내1
Identify the key observations from the problem: a precipitate formed and the test tube got very warm.
Understand the concept of exothermic and endothermic reactions: Exothermic reactions release heat, causing the surroundings to become warmer, while endothermic reactions absorb heat, causing the surroundings to become cooler.
Relate the temperature increase to the type of reaction: Since the test tube got very warm, this indicates that heat was released into the surroundings, which is characteristic of an exothermic reaction.
Clarify the nature of a precipitate: A precipitate is a solid that forms from a solution during a chemical reaction, typically as a result of the reaction between two soluble compounds. It is not necessarily an element; it can be a compound.
Conclude based on the observations and concepts: The process is exothermic, as indicated by the release of heat, and thus has a negative value for heat (enthalpy change).
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