作者：Rameen Sarwar 4 月以前
18
Thermodynamics
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Rates
The study of thermodynamics involves understanding enthalpy changes in chemical reactions, where the total enthalpy change remains constant regardless of the reaction pathway, according to Hess'
開啟
Thermodynamics
&
Rates Enthalpy (ΔH) Thermochemical Equations: Represent reactions with ΔH Molar Enthalpy (ΔH/m): Heat change per mole of substance Heat Transfer ΔT: Change in temperature (°C) c: Specific heat capacity (J/g°C) m: Mass of substance (grams, g) Q: Heat energy (Joules, J) Equation: Q = mcΔT Calorimetry Calculate heat (Q) using Q = mcΔT Measure temperature change (ΔT) Mix reactants in the calorimeter Procedure: Types of Calorimeters: Coffee cup (constant pressure), bomb (constant volume) Purpose: Measure heat absorbed or released during a chemical reaction Factors Affecting Rates Concentration: Higher concentration increases reaction rate Catalysts: Lower activation energy, increase reaction rate Surface Area: Greater surface area increases reaction rate Temperature: Higher temperature increases reaction rate Calculating Reaction Rates Conductivity: Change in ionic concentration over time pH: Change in acidity over time Volume: Change in gas volume over time Mass: Change in mass over time Instantaneous Rate: Rate at a specific moment Average Rate: Change in concentration over time Hess' Law
Subtopic Application: Combine steps to find overall ΔH Principle: Total enthalpy change is the same regardless of the route taken Energy Changes in Reactions Energy Diagrams: Show energy changes during reactions Endothermic Reactions: Net absorption of energy (e.g., photosynthesis) Exothermic Reactions: Net release of energy (e.g., combustion) Bond Breaking: Requires energy (endothermic) Bond Formation: Releases energy (exothermic)
