Enthalpy Change ∆H Of A Reaction - Reaction Enthalpy
Chapter Name : Thermodynamics |
Sub Topic Code : 102_11_06_04_03 |
Topic Name : Enthalpy Change ∆H Of A Reaction - Reaction Enthalpy |
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Sub Topic Name : Enthalpy Changes During Phase Transformations |
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Introduction
• Phase transformation from 1 state to another involves energy change. • This energy change at constant pressure is called as enthalpy change of phase transformation. • Enthalpy change is positive for exothermic reactions and negative for endothermic reactions. • The magnitude of enthalpy change depends on strength of intermolecular interactions.
Pre-Requisites:
• Thermodynamic terms • The state of a system • Enthalpy
Activity:
Melting of ice, evaporation of water.
Real Life Question:
How to calculate enthalpy change during phase transformation?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| Enthalpy | It is same as energy at low and moderate pressure. |
| Standard enthalpy of fusion | It is the enthalpy change that accompanies melting of one mole of a solid substance in standard state. |
| Standard enthalpy of vaporization | It is the amount of heat required to vaporize one mole of a liquid at constant temperature and under standard pressure (1bar). |
| Standard enthalpy of sublimation | It is the change in enthalpy when one mole of a solid substance sublimes at a constant temperature and under standard pressure (1bar). |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| NCERT Chemistry 11 Table 6.1 | It gives the value of standard enthalpy change of different substances |
| Ice | When you heat ice, it melts. Thus enthalpy change takes place. |
Real life uses :
Calculation of enthalpy change associated with phase transformations.
Places to visit :
Home.
Practical examples around us
| Examples | Explainations |
|---|---|
| Melting of ice | On heating ice, it melts. Thus enthalpy change takes place due to absorption of heat. |
What you learn in Theory:
Calculation of enthalpy change associated with phase transformations.
What you learn in Practice:
Calculation of enthalpy change associated with phase transformations.