### Enthalpy vs. Entropy Graphing Tool

This tool is designed
to help you understand the effects of reaction enthalpy (DH°_{rxn})
and entropy (DS°_{rxn})
changes and temperature on the standard state Gibbs free energy
change (DG°_{rxn}).
In the "Qualitative" version, which appears first, gauges
fill in the positive and negative directions for DS°
and DH°
as the plot is adjusted.

Favorable parameters
for a spontaneous reaction are indicated by the color green and
non-favorable parameters are shown in red. If you are having trouble
understanding the graphing tool, the questions below are designed
to help you sort out the variables.

Instructions
for using the Graphing Tool

Table
of Thermodynamic Data

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Observe
what happens to the DH°
and DS°
indicators when you leave the y-intercept the same and use the
endpoint of the line to adjust the slope.
What happens if you
move the y-intercept instead?

Think about what is
represented by the :

Can you find a favorable reaction temperature when DH°
is positive? What sign is DS°?

When both DS°
and DH°
are negative, what temperatures (high or low) favor the reaction?

Click
on the endpoints of the graph to move the line and change DH°_{rxn}
and DS°_{rxn}.
Use the + and - to change the temperature scale. The "Qualitative"
and "Quantitative" buttons switch back and forth between
two versions of the tool. The
gauges in the "Qualitative" version only show up to
200 J/mol-K for DS°
and 500 kJ/mol-K for DH°. If you want to see values above
(or below for negatives) those, you need to switch to the "Quantitative"
version. The "Quantitative" version allows you to type
values for DH°_{rxn}
and DS°_{rxn
}into input boxes. Because
of computer screen limitations, these values will change slightly
once you hit enter or click in the graph area to input the data.
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