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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 14th EditionCh.5 - ThermochemistryProblema 124
Capitolo 5, Problema 124

The precipitation reaction between AgNO3(aq) and NaCl(aq) proceeds as follows: AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(s). (b) What would you expect for the value of _x001F_H° of the overall molecular equation compared to that for the net ionic equation? Explain.

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Identify the overall molecular equation: AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(s).
Write the net ionic equation by removing the spectator ions (Na+ and NO3-): Ag+(aq) + Cl-(aq) → AgCl(s).
Understand that the enthalpy change (ΔH°) for a reaction is related to the bonds broken and formed during the reaction.
Recognize that the overall molecular equation includes the formation of NaNO3(aq), which does not occur in the net ionic equation.
Conclude that the ΔH° for the overall molecular equation may differ from the net ionic equation due to the presence of additional processes (e.g., dissolution of NaNO3) in the overall equation.

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Precipitation Reactions

Precipitation reactions occur when two aqueous solutions react to form an insoluble solid, known as a precipitate. In this case, AgCl is formed from the reaction of AgNO3 and NaCl. Understanding the formation of precipitates is crucial for predicting the products of reactions and their thermodynamic properties.
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Selective Precipitation

Enthalpy Change (_x001F_H°)

Enthalpy change (_x001F_H°) refers to the heat content change during a chemical reaction at constant pressure. It is a key factor in thermodynamics, indicating whether a reaction is exothermic (releases heat) or endothermic (absorbs heat). The overall enthalpy change can differ between the complete molecular equation and the net ionic equation due to the cancellation of spectator ions.
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Enthalpy of Formation

Net Ionic Equations

Net ionic equations represent the actual chemical species that participate in a reaction, excluding spectator ions that do not change during the reaction. This simplification helps in analyzing the essential components of a reaction, particularly in terms of energy changes and reaction mechanisms, which is important for understanding the enthalpy changes associated with the reaction.
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Net Ionic Equations
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