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moonlight93

  • one year ago

Label the enthalpy changes shown in the diagram below. I need help with chemistry please.

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  1. moonlight93
    • one year ago
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    This is the diagram that I need to label. I looked in my chm book to get an idea, but it wasn't helping. and my professor did not explain this at all.

  2. butterflydreamer
    • one year ago
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    hmm.. Solid -> Gas This process is called "Sublimation" The opposite of sublimation (solid -> gas) is deposition (gas -> solid) \[\Delta H _{sublimation} = -\Delta H_{deposition}\] Solid -> Liquid This process is called "Fusion (Melting)" \[\Delta H_{fusion} = H_{liquid} - H_{solid} \] Liquid -> Solid This process is called "Solidification (Freezing)" Note: this is the opposite process of fusion/melting and therefore, the enthalpy for the opposite process (freezing) will be exactly EQUAL but opposite in sign. \[\Delta H_{freezing} = H_{solid} - H_{liquid} \] \[= -\Delta H_{fusion}\] Finally we have: Liquid -> Gas This process is called "Vaporisation" and the opposite process Gas -> Liquid This process is called "Condensation" \[\Delta H_{vaporisation} = -\Delta H _{condensation}\]

  3. butterflydreamer
    • one year ago
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    All you really need to know is the differences and changes in states and use the formulas and you'll be fine :)

  4. butterflydreamer
    • one year ago
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    Also note that phase changes are accompanied by energy and enthalpy changes. - Vaporisation, melting and sublimation are ALWAYS ENDOTHERMIC, meaning that energy must be ABSORBED to overcome the intermolecular forces. -Condensation, freezing and deposition are ALWAYS EXOTHERMIC, meaning that energy must be RELEASED as the molecules get closer and attract each other. Heat of vaporisation \[\Delta H _{vap} \] - enthalpy change for the conversion of 1 mol of a substance from liquid to gas. Heat of fusion \[\Delta H_{fus} \] - enthalpy change for the conversion of 1 mol of a substance from solid to liquid. Heat of sublimation \[\Delta H_{sub}\] - enthalpy change for the conversion of 1 mol of a substance from solid to gas.

  5. moonlight93
    • one year ago
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    thank you for explaining :). does this look right to you? @butterflydreamer

  6. butterflydreamer
    • one year ago
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    no probleeem :). Yeeeep, all of your answers are correct! Excellent job

  7. moonlight93
    • one year ago
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    thanks for helping .

  8. butterflydreamer
    • one year ago
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    no worries!

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