OpenStudy (moonlight93):

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

2 years ago
OpenStudy (moonlight93):

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 years ago
OpenStudy (butterflydreamer):

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" $\Delta H_{vaporisation} = -\Delta H _{condensation}$

2 years ago
OpenStudy (butterflydreamer):

All you really need to know is the differences and changes in states and use the formulas and you'll be fine :)

2 years ago
OpenStudy (butterflydreamer):

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.

2 years ago
OpenStudy (moonlight93):

thank you for explaining :). does this look right to you? @butterflydreamer

2 years ago
OpenStudy (butterflydreamer):

no probleeem :). Yeeeep, all of your answers are correct! Excellent job

2 years ago
OpenStudy (moonlight93):

thanks for helping .

2 years ago
OpenStudy (butterflydreamer):

no worries!

2 years ago