Introduction
In previous lessons, we considered thermodynamic properties such as the
deliquescence, water uptake, and gas/particle partitioning of particles
at a fixed temperature of 298.15 K. In Lessons 7 to 9 we examine
how these properties depend on temperature.
Preparation
Before starting, ensure that this browser window occupies only the
left half of your screen. You should leave enough
space for another browser window where you can
enter data into
E-AIM and read the results. If your screen is too small for
two windows, print out this tutorial and use this window to
run the
E-AIM model. In these lessons we assume that you will
have two browser windows open.
Select this
link to open a second browser window containing the data
input page for "variable temperature" calculations
using Model II (http://www.aim.env.uea.ac.uk/aim/model2/mod2t.php). Arrange
the windows on your screen so that both are visible and the left window
contains this text.
The Lesson
This consists of the two sets of calculations described in the links below,
which should be done in the order listed.
You have completed Lesson 7, and learned that:
- The water content of particles
is a relatively weak function of temperature. In the two simple strong electrolyte
solutions examined here the water activity coefficient in the aqueous phase
and the water content of the particle both increase, by about 10% for
NH4NO3 and 1.5% for
(NH4)2SO4 between 275 K and
300 K.
- In a more complex solution such as aqueous H2SO4,
in which there is a chemical equilibrium between the HSO4−
and SO42− ions, the activity
coefficient and water content changes are not as easy to predict. For the
H2SO4 solutions
studied here the influence of the equilibrium reaction on water uptake – via
the total number of ions – appears to dominate water uptake. This results in
a decrease in the water uptake by about 2% from 275 K to 300 K.
Now proceed to Lesson 8 to explore how
solid/aqueous phase transitions (deliquescence) vary with temperature.