Standard Enthalpies of Formation Basics

Moderators: Chem_Mod, Chem_Admin

Ethan_Kato_1D
Posts: 25
Joined: Fri Jul 15, 2016 3:00 am

Standard Enthalpies of Formation Basics

Postby Ethan_Kato_1D » Fri Jan 13, 2017 9:34 pm

I am confused about how to find the standard states of compounds and elements for standard Enthalpies of formation. How do you know what state to use for each element and compound?

Fengting Liang 1F
Posts: 23
Joined: Sat Jul 09, 2016 3:00 am

Re: Standard Enthalpies of Formation Basics

Postby Fengting Liang 1F » Fri Jan 13, 2017 10:04 pm

Usually how I think of it is if it's just the element alone, like C or Na or Ag, they're in their "standard state," unless they're diatomic gases like O2 or F2 which are also in their standard states. But a compound like CO2 isn't in a standard state and therefore you'd have to look up its standard enthalpy of formation. And I'm pretty sure the equation would usually give the states of matter of the compounds in the reaction.

Rachel Kipp 1I
Posts: 16
Joined: Wed Sep 21, 2016 2:55 pm

Re: Standard Enthalpies of Formation Basics

Postby Rachel Kipp 1I » Fri Jan 13, 2017 10:10 pm

A helpful way to remember the diatomic molecules is with the following saying: Have No Fear Of Ice Cold Beer

H=H2
N=N2
F=F2
O=O2
I=I2 (solid)
C=Cl2
B=Br2 (liquid)


Return to “Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)”

Who is online

Users browsing this forum: No registered users and 2 guests