00:00:05
welcome to environmental chemistry so
00:00:07
you have this kind of skeletal notes um
00:00:10
starting with basically the ILO the
00:00:13
intended learning outcome for this
00:00:14
specific lecture for example in this
00:00:16
lecture we're going to evaluate the
00:00:19
basics of water chemistry and then we're
00:00:21
going to understand the basics of
00:00:24
speciation and then at the end better
00:00:26
understanding the features and impact of
00:00:28
water in environmental system so this is
00:00:31
this would be the basics of what we're
00:00:33
going to learn and what we're going to
00:00:34
expect from this specific
00:00:37
exure so uh we kept using this
00:00:40
environmental system over and over but
00:00:42
environmental system is similar to any
00:00:44
other system that we are normally
00:00:46
dealing with uh three different phases
00:00:49
so let's say if this is a liquid
00:00:55
phase like a lake then you might have
00:00:58
some solid
00:01:01
sitting in the bottom of this liquid
00:01:03
phase or some
00:01:06
outside then you have also a gas
00:01:09
phase and it's all about the interaction
00:01:13
between these
00:01:14
phases interaction between the liquid
00:01:17
phase the gas phase solid and the liquid
00:01:20
and also solid and the gas phase so this
00:01:24
this interaction is very important at
00:01:27
the equilibrium we're going to talk
00:01:29
about the equilibrium later but this
00:01:31
would be basically everything when it
00:01:32
comes to investigating a system
00:01:35
including an environmental system which
00:01:37
basically includes all of these three
00:01:40
phases and when we look at environmental
00:01:43
system specifically we see that the
00:01:47
core of environmental
00:01:51
system is basically the liquid face
00:02:01
so instead of looking at each individual
00:02:06
interaction you basically have this core
00:02:09
liquid phase and then redefine the
00:02:12
system as the interaction between the
00:02:14
liquid and the gas phase liquid and the
00:02:17
solid phase so which again represent
00:02:20
most of the environmental system of
00:02:22
course we have some interaction between
00:02:24
solid and the gas phase but as you as
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you'll see most of the interaction is
00:02:29
around the liquid liid face and also the
00:02:31
liquid face species inside the liquid
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face
00:02:36
and in
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particular the most important liquid
00:02:43
phase environmental system is basically
00:02:53
water so it's fair to assume this course
00:02:57
mostly covers water
00:03:00
chemistry so it's basically water
00:03:02
chemistry and how we can Define the
00:03:05
interaction between that water with the
00:03:07
gas phase with the solid phase which
00:03:10
would be the individual chapters of this
00:03:14
course so I mentioned that we have many
00:03:18
bodies of water in environmental system
00:03:21
what are some of the examples I go with
00:03:24
ocean for example what else we
00:03:28
have what's that
00:03:30
Rivers yeah very
00:03:33
common
00:03:37
Lakes um it does it's a liquid but it's
00:03:41
a solid face I mean unless you visit in
00:03:44
summer after global warming and stuff
00:03:47
but uh but let's put that aside like
00:03:50
that's a solid facee what
00:03:52
else exactly underground Waters
00:03:59
soorry my handwriting is a little
00:04:06
bit and so on but what is the most
00:04:09
important
00:04:12
one ocean any
00:04:15
objection the most important body of
00:04:20
water
00:04:23
anywhere could be the ocean
00:04:32
it's actually you you're 60%
00:04:36
water any objection on that so
00:04:40
basically we are an environmental system
00:04:43
could be an environmental system which
00:04:46
almost
00:04:48
60% of water so whatever we learn here
00:04:51
in this course can be applied to
00:04:53
anything example some of the classic
00:04:56
example that we're going to overview is
00:04:58
an environmental application for example
00:05:00
acid base toxicity but this could be
00:05:03
applied to any system including
00:05:05
biological system including our system
00:05:07
so for example we have pH in our system
00:05:11
in our guts for example acid
00:05:15
base uh we have salt in our
00:05:19
body so we talk about hydration
00:05:22
dehydration in that context we also have
00:05:25
tons of
00:05:27
metals example we talk about
00:05:30
iron deficiency and those sort of stuff
00:05:32
so that basically whatever we learn
00:05:34
again here can be applied there so
00:05:36
whatever Redux chemistry we reading here
00:05:39
inside the lake is basically the same
00:05:41
concept also in your
00:05:54
body so again the course focuses on
00:05:58
chemical reactions in water and the
00:06:01
interaction between water and other
00:06:05
faces so this is normally called also
00:06:07
sometimes aquous chemistry or aquatic
00:06:09
chemistry so if you hear those courses
00:06:13
is basically pretty much the same when I
00:06:15
took this course uh which by the way was
00:06:18
probably the most useful course they
00:06:20
took and I was so interested also to
00:06:22
teach this uh it was titled aquatic
00:06:27
chemistry uh the reason I'm saying it
00:06:29
was very useful because I was working in
00:06:31
the lab I was just mixing some Sals
00:06:33
together then after this course I knew
00:06:36
what what exactly I have in the system
00:06:38
initially I thought this is sodium
00:06:40
sulfate that I'm mixing so I have sodium
00:06:42
and sulfate and that's it but now I have
00:06:45
and now I know probably I have more than
00:06:48
10 species in my system which can
00:06:50
explain so many of the observation that
00:06:53
I had in the
00:06:54
LA
00:06:56
so um
00:06:59
one good news is that we're talking
00:07:02
about inorganic chemistry so no organic
00:07:05
involvement if you took organic
00:07:07
chemistry you know this is not the
00:07:09
easiest course and we're not going to
00:07:11
involve any Organics in this course it's
00:07:13
all about
00:07:14
inorganic uh in the context of water
00:07:18
chemistry so we have some assumption in
00:07:21
this course and that we're going to
00:07:23
assum uh pretty much for the whole uh
00:07:27
semester the very first one
00:07:30
is this big equilibrium assumption we're
00:07:32
talking about the equilibrium we're not
00:07:34
talking about any transition state so
00:07:37
you know for example when you're adding
00:07:39
a sugar to your coffee when you're
00:07:40
mixing it before it gets to that
00:07:42
equilibrium you're passing the
00:07:44
transition phase we can talk about
00:07:46
transition phase uh just in that could
00:07:50
be an independent course by itself but
00:07:52
here we're talking about the state that
00:07:55
your coffee is suweet and that's it we
00:07:58
reach to that equilibrium so all the
00:08:00
equations that we're solving behind our
00:08:02
mind the big assumption is that we're
00:08:05
solving for
00:08:06
equilibrium so that's the very first
00:08:09
assumption to describe
00:08:11
equilibrium which mean it means more
00:08:14
specifically or more Technically when we
00:08:16
talk about equilibrium we talk about
00:08:19
both thermodynamic and kinetic or make
00:08:23
it a little bit simplified this means
00:08:26
the system
00:08:30
is at a
00:08:34
stable energy
00:08:38
state it might be a little bit fake but
00:08:40
we're going to talk about this in
00:08:42
lecture four and five so but in terms of
00:08:46
the energy State it's stable so that's
00:08:49
one approach to look at the equilibrium
00:08:51
the other approach which is probably
00:08:53
more familiar is basically the
00:08:56
concentration doesn't change so the
00:08:58
concentration of species
00:09:09
remains
00:09:14
constant over time so that's
00:09:17
basically the key here for the change in
00:09:21
the concentration of species I over time
00:09:25
this is basically zero
00:09:32
or technically speaking the rate of
00:09:34
producing and consuming that species is
00:09:36
the same so it's from the kinetic point
00:09:39
of view that's basically the equilibrium
00:09:41
the definition of equilibrium but for
00:09:43
now basically the concentration doesn't
00:09:47
change so why do you think this
00:09:51
assumption is appliable to environmental
00:09:56
systems is it just for the sake of
00:09:58
simplic
00:10:02
or it's very
00:10:08
practical can we say environmental
00:10:11
systems generally
00:10:13
speaking are at
00:10:17
equilibrium you have this Lake sitting
00:10:21
there for a long
00:10:24
time
00:10:25
so relatively speaking compared to let's
00:10:28
say chemical system
00:10:30
the concentration of species it doesn't
00:10:32
change much you know some biological
00:10:35
consumption maybe is happening there but
00:10:37
it reaches equilibrium so they're like
00:10:40
lazy system in terms of the
00:10:42
interaction the composition of sea water
00:10:44
in terms of what is there is pretty much
00:10:49
uh at equilibrium it doesn't change that
00:10:52
fast so we're talking about the time I
00:10:54
know climate change is impacting that
00:10:56
but it's not very significant again
00:10:58
relatively speaking
00:10:59
compared to a chemical system that you
00:11:01
have a catalysis combining the two and
00:11:03
then it's just changing very fast so
00:11:08
it's fair to
00:11:10
say uh most of environmental system is
00:11:13
already at equilibrium
00:11:37
the other reason that is fair to assume
00:11:41
that at equilibrium is that if there is
00:11:43
a
00:11:44
disruption they reach equilibrium very
00:11:55
fast for example when we talk about acid
00:11:58
base
00:12:02
they reach equilibrium less than 1
00:12:06
second in
00:12:08
average so you have only one second of
00:12:11
transition
00:12:13
time and the rest is basically it
00:12:16
establish equ equilibrium very fast so
00:12:19
because of these two it's fair to assume
00:12:22
that um always when we talk about
00:12:24
environmental system we have this
00:12:26
equilibrium assumption
00:12:31
one of the problem with climate change
00:12:32
is basically it's interrupting and some
00:12:35
of this um they don't reach equilibrium
00:12:37
very fast the fact that it's changing is
00:12:39
a problem and also some of them are like
00:12:41
at a very slow transition state so
00:12:43
that's another problem from the
00:12:45
equilibrium point of view so that's one
00:12:48
assumption we have we always use it and
00:12:50
when we have for example chemical
00:12:53
equilibrium which is uh lecture three we
00:12:58
dig deeper on this
00:12:59
so it it it
00:13:01
simplifies uh so many of the equations
00:13:03
that we're dealing with down the road
00:13:06
the other term that we're going to use a
00:13:08
lot probably uh one of the most
00:13:12
important uh um terminology that we're
00:13:15
going to use in this course is
00:13:16
speciation so you've heard this before
00:13:19
here and there but here we just want to
00:13:21
make sure we are on the same page so
00:13:23
when we talk about speciation we're
00:13:25
talking about unique entities so that's
00:13:27
basically the keyword here
00:13:30
so they're like different forms it could
00:13:33
be it could originate from the same
00:13:35
element but when we have unique entities
00:13:38
which are different in terms of chemical
00:13:40
formula or oxidation state so then we
00:13:44
have a new
00:13:46
species um for example when we talk
00:13:49
about some
00:13:51
nitrogen containing
00:13:55
species then we have probably so many
00:13:58
different unique entities any
00:14:02
example what are some of
00:14:08
the I start with
00:14:12
ammonia doesn't smell
00:14:15
good I worked with Ammon for three years
00:14:18
so still gives me
00:14:21
headache what else that contains
00:14:23
nitrogen at is a unique
00:14:26
entity so in two yeah
00:14:30
we're breathing it so when we talk about
00:14:33
ammonia we also can
00:14:36
mention
00:14:39
ammonium very similar but unique entity
00:14:42
because it's different in terms of both
00:14:45
chemical formula and not let's not talk
00:14:48
about the oxidation state now it's a
00:14:50
different chemical
00:14:52
formula what else
00:14:55
nitrate a big Topic in environmental
00:14:58
systems
00:15:01
nitric
00:15:05
acid and something like
00:15:08
n2o anyone knows the nickname for
00:15:13
n2o yeah exactly so laughing
00:15:19
gas some funny videos on YouTube if
00:15:22
you're so so these are unique entities
00:15:25
all containing nitrogen
00:15:29
but it doesn't matter they are unique
00:15:31
and later you'll see that they have also
00:15:32
unique features sometimes very different
00:15:35
features and in terms of the oxidation
00:15:38
state so for example some of the
00:15:42
iron containing
00:15:46
species it could
00:15:48
be Iron 2+ or it could be Iron 3+
00:15:54
here um the same chemical formula in
00:15:57
terms of the both contain only ion
00:15:59
element but different oxidation state
00:16:02
going to talk about that in chapter
00:16:10
four so as I mentioned
00:16:13
um accounting for speciation in water is
00:16:16
very important because some of these
00:16:19
they have like completely different uh
00:16:22
properties so for example if fe2+ is
00:16:27
toxic if fe3+ is not toxic then we can
00:16:33
design a process to convert fe2+ to fe3
00:16:37
plus so that sort of information we're
00:16:39
going to gain in this course for this
00:16:41
example for example chapter four so this
00:16:44
is um uh something that playing with
00:16:46
speciation is one of our jobs here so to
00:16:50
give an example of how dramatically
00:16:52
different um some of these features
00:16:54
could be we can look at U
00:16:57
sulfate s so4 2
00:16:59
minus and
00:17:01
H2S both containing sulfur but as you
00:17:06
can imagine these two have like
00:17:08
significantly different features so this
00:17:10
is other or
00:17:13
less anyone knows what's the smell
00:17:17
of exactly rotten
00:17:22
xgs so sulfate
00:17:26
is nonvolatile
00:17:31
it's a very nice species just sits in
00:17:34
the a phase it's a nice
00:17:37
background car you're using it a lot
00:17:40
probably it's very
00:17:43
nice H it's not toxic
00:17:51
also but this guy is very
00:17:55
volatile and it's very toxic
00:18:02
so if you're working with H2S you really
00:18:04
need to be careful on the lab they are I
00:18:07
think a specific line of safety designed
00:18:10
for H2 so you need
00:18:13
to like special sensors and the the
00:18:17
limit is very low for the safety limit
00:18:20
for these gas so anyway just showing you
00:18:23
that entities or species is it's
00:18:26
important what kind of species we're
00:18:28
talking about
00:18:29
and you're going to see that a lot in
00:18:31
this
00:18:32
course uh just to give you an example uh
00:18:35
this is basically some tables that
00:18:37
you're are going to see in scientific
00:18:40
literature in textbook here what is
00:18:42
showing is different species up to here
00:18:46
in different bodies of water or in
00:18:48
different samples and it shows it
00:18:51
highlights how significantly different
00:18:53
could be for example looking at uh
00:18:56
magnesium in Great Salt Lake
00:19:00
7200 compared to like one in saana River
00:19:04
so same element the same species was
00:19:07
significantly different so if your
00:19:09
startup is harvesting magnesium 2 plus
00:19:12
it's better to locate somewhere near
00:19:15
Great Salt Lake compared to somewh like
00:19:20
you can just say on intaking some Rivers
00:19:22
so it really matters what you're
00:19:24
intaking uh in terms of the species as
00:19:27
you know from General chemistry stre
00:19:29
some of them are
00:19:30
C or positively charged species some of
00:19:33
them are
00:19:34
anions or negatively charged species and
00:19:38
sometimes in these tables they also talk
00:19:40
about uh some of the features related to
00:19:43
the sample this is alinity we have one
00:19:46
lecture on alkalinity a very important
00:19:48
metric pH probably the most familiar
00:19:52
unit here and dissolve organic carbon so
00:19:55
again some of the features related to
00:19:57
that samp it's just an
00:19:59
example and also some metals the
00:20:02
presence of different Metals in
00:20:04
different game samples
00:20:08
collector so keep in mind this is the
00:20:11
total amount of metal in this sample one
00:20:14
of our job would be later if you're
00:20:17
given this information and you're given
00:20:19
the pH of the solution you're able to
00:20:22
describe what kind of copper you have do
00:20:25
you have copper 2+ do you have copper
00:20:29
um hydroxide do you have copper
00:20:31
hydroxide 2 neutral charged or O3 minus
00:20:36
tons of different species so it's your
00:20:39
job to decouple the species or different
00:20:42
species that uh all of them together
00:20:45
would be this total value for this
00:20:48
element so um most of our analytical
00:20:52
methods that we use um rely on measuring
00:20:55
the total value like ICP for example but
00:20:58
some of them are specifically for U for
00:21:01
different ions for example ion
00:21:03
chromatography so later we're going to
00:21:05
talk about that just just an example of
00:21:08
what we're going to cover in this
00:21:13
course so um I think it's because we're
00:21:16
going to talk about water a lot uh it's
00:21:19
good to overview some of the concept
00:21:21
that we had before in general chemistry
00:21:24
sometimes even high school chemistry but
00:21:26
it's good to be all on the same page
00:21:28
when we talk about water and why water
00:21:30
is important the very first thing is
00:21:33
because water is polar and as we know it
00:21:36
has uh dipoles
00:21:40
so when we look at a water
00:21:43
molecule uh it's a great solvent
00:21:47
for because of this polarity we have a
00:21:51
region that is relatively
00:21:56
speaking electron poor
00:22:00
or it has a positive
00:22:08
dipole and we have a
00:22:10
region that is
00:22:13
basically again
00:22:15
relatively compared to the other side is
00:22:18
electron
00:22:20
rich or it has a negative typ
00:22:29
so this feature by itself can explain
00:22:33
the diversity of species in water uh
00:22:38
that we just saw in the other table
00:22:40
because just a polar it's a great
00:22:43
solvent for for example charge
00:22:50
species so those species that uh they're
00:22:54
very soluble in water called hydrophilic
00:22:58
or water
00:23:00
loving and species that are not very
00:23:02
soluble they're like
00:23:05
hydrophobic because of this mainly
00:23:08
because of this
00:23:10
feature and the reason little bit
00:23:13
digging deeper is that is all about the
00:23:15
coordination chemistry we're not going
00:23:17
to talk about the details of
00:23:18
coordination chemistry but it's the fact
00:23:21
they can um this partial negative and
00:23:24
positive charge can Orient around this
00:23:27
charge species
00:23:29
so they can uh make it soluble so let's
00:23:32
say if you have positively
00:23:35
charged okay this is very simplified but
00:23:39
it basically it
00:23:41
reorients water molecules in a way
00:23:45
that
00:23:47
um it dissolves it
00:23:56
eventually so the actual number numbers
00:23:58
of water's molecules in this case is
00:24:01
four G is a
00:24:03
technical uh could be a technical
00:24:06
lecture by itself but it's just all
00:24:08
about the coordination chemistry that
00:24:09
we're not covering I just want to
00:24:11
highlight it the positively charged
00:24:14
attracts the negative dipole and it
00:24:18
coordinates around the charge so it
00:24:21
dissolves this charge so that's why this
00:24:24
could be a very hydrophilic species
00:24:26
that's why you see a lot of sodium
00:24:29
in water so that's very
00:24:31
solid the opposite thing happen for a
00:24:33
negatively charged species basically the
00:24:36
same thing is happening but here is from
00:24:38
the opposite
00:24:40
dipole that is orienting
00:24:46
around in this case it would be
00:25:06
because of the same reason non-polar
00:25:09
molecules can also dissolve in water but
00:25:12
they have very low
00:25:14
solubilities what is the most classic
00:25:17
example of
00:25:18
a
00:25:21
insoluble
00:25:23
thing oil exactly oil and
00:25:27
water what about
00:25:33
gases methane for
00:25:37
example
00:25:39
hydrogen the big one I'm missing
00:25:45
here
00:25:48
oxygen so oxygen is roughly I guess 9
00:25:51
PPM the the solubility in
00:25:54
water uh it's enough for biological
00:25:58
assistance uh but this time when I was
00:26:01
traveling I saw a bottle of water that
00:26:03
was uh advertised as a
00:26:06
high oxygen containing whatever kind of
00:26:09
water and I was wondering this is not
00:26:12
possible based on lecture one so that
00:26:16
would be probably one of the uh question
00:26:18
in your
00:26:19
exam uh that you're going to answer that
00:26:22
but you need to wait by the end of
00:26:24
chapter two you'll figure it out why
00:26:27
it's kind of
00:26:31
doable let me
00:26:37
guess they were selling that
00:26:42
so so we wait probably the uh end of
00:26:48
chapter to what's that sure uh So based
00:26:52
on this lecture we know oxygen in water
00:26:55
has like a low
00:26:56
solubility and also uh we know there's a
00:27:00
limit like roughly I guess 9 PP I'm not
00:27:02
very sure but there's a limit so then
00:27:05
you advertise your product to have like
00:27:07
a very high concentration of water
00:27:09
oxygen in
00:27:10
water so then what's the
00:27:14
reason this probably part of the exam so
00:27:19
uh but the reason is pretty simple they
00:27:22
can do that but it's I'm not sure how
00:27:25
far they can go in terms of the amount
00:27:27
of oxygen
00:27:30
the other uh
00:27:32
important assumption we have when it
00:27:35
comes to water this is this looks very
00:27:37
simple but this is basically the key for
00:27:39
half of your calculation in chapter two
00:27:42
it's electrically neutral so that means
00:27:46
you don't have a water that is
00:27:48
positively charged or negatively charged
00:27:50
if you see that bottle just throw it
00:27:52
away for sure it's um it's not possible
00:27:55
so always the sum of positive
00:28:02
charge is equal to the sum of negative
00:28:14
charge so OB base so you cannot
00:28:18
introduce one mole of sodium into water
00:28:22
you have to compensate it with for
00:28:24
example one mole of colorine to water so
00:28:28
the
00:28:29
overall uh later uh in the next page
00:28:32
we're going to talk about ionic strength
00:28:34
but even at higher ionic strength you
00:28:36
might have more ions but again the same
00:28:41
assumption also the same rule applies
00:28:45
the sum of negatively charge is equal to
00:28:47
sum of the positively charge so again
00:28:49
this would be the core of calculation in
00:28:51
chapter four um one of that degree of
00:28:55
Freedom type of equation that you're
00:28:56
looking for to solve of a equation an
00:28:59
equation so that's uh something that
00:29:01
we're going to cover
00:29:04
later um so we talked about species we
00:29:09
talked about species in water but now we
00:29:12
want to quickly talk about what type of
00:29:15
reactions create species in
00:29:18
water um the very first one is water
00:29:22
ionically dissociates so basically you
00:29:26
always have water in the form of
00:29:30
liquid dissociating or in equilibrium
00:29:33
with
00:29:34
proton in the aquous phas plus
00:29:38
hydren again very basic but very
00:29:43
important so there's no
00:29:46
water without proton or hydroxide you
00:29:50
might have neutral water in terms of pH
00:29:53
but it doesn't mean that the
00:29:54
concentration of each is zero but it
00:29:56
means the concentration of proton and
00:29:58
hydroxide is the same so we always have
00:30:03
this reaction so later chapter 2 three
00:30:06
and four this is the very first reaction
00:30:09
that we write when we're going for the
00:30:11
calculation so water dissociates to
00:30:15
proton and
00:30:21
hydroxide so that's one way to introduce
00:30:25
species to water so basically Water by
00:30:28
self dissociates and it's in
00:30:30
equilibrium uh the other method is
00:30:32
basically you add a salt you have a salt
00:30:35
on the Shelf you added to B it cause a
00:30:39
reaction that introduces more species to
00:30:42
bother this might sound a bit fancy but
00:30:44
what we're talking about is basically a
00:30:46
simple dissociation reaction you have a
00:30:50
salt that either fully dissociates or is
00:30:54
in equilibrium so this means right now
00:30:56
this example is fully dissoci species or
00:30:59
it could be in
00:31:01
equilibrium to
00:31:04
other uh species
00:31:10
so so basically what I'm doing is
00:31:13
introducing two species to
00:31:16
Water by dissolving one salt or it could
00:31:21
be opposite I add more and more sodium
00:31:24
like let's say sodium sulfate then this
00:31:26
reaction start shifting this way then
00:31:28
I'm introducing a new species which is
00:31:31
leaving the system which is in the solid
00:31:33
phase that's chapter
00:31:38
three uh one very important group of U
00:31:42
reactions that introduce species is
00:31:44
basically acid based so you might have
00:31:48
an acid either weak or strong we're
00:31:51
going to talk about that terminology
00:31:53
later that
00:31:56
could also introduce species to
00:32:02
water or it could be a
00:32:20
base so we're going to talk cover this
00:32:23
one
00:32:24
all in chapter two
00:32:30
how we deal with an acid based reaction
00:32:33
and what are the
00:32:34
consequences the very obvious one is the
00:32:36
pH might
00:32:38
change uh but it also impacts a lot of
00:32:41
other
00:32:43
speciations um gases that that can also
00:32:47
interact with water so for example when
00:32:50
you have ammonia gas in the form of gas
00:32:56
it can be in equilibrium
00:33:00
so by exposing your water to a gas
00:33:04
you're basically
00:33:06
introducing this gas or this new species
00:33:09
is in the aquous
00:33:11
phase the most classic example is carbon
00:33:14
dioxide we're going to talk about that
00:33:17
and this might impact so many other
00:33:20
reactions in water that's again what
00:33:23
we're going to cover so this would be
00:33:26
also chapter two
00:33:34
uh the other um form could be metals
00:33:38
like when we have let's say
00:33:40
fe2+ in the aquous
00:33:43
form if you also have CL
00:33:46
minus just as an example you can
00:33:49
potentially have a complex in your
00:33:54
system so you introduce this or if you
00:33:57
have this complex it could go back to
00:33:59
produce fe2+ and cl minus so this is all
00:34:03
in chapter
00:34:12
3 another example could be basically
00:34:16
exchange of
00:34:17
electron or Redux reaction oxidation
00:34:21
reduction type of
00:34:23
reaction uh one of the simplest example
00:34:25
or the classic example they use in the
00:34:28
aquous phase you have fe3+ you provide
00:34:31
one
00:34:32
electron then you have
00:34:35
fe2+ in the system and you can go back
00:34:38
and forth between this two species or
00:34:41
for water
00:34:42
itself could
00:34:47
be producing oxygen in the gas form then
00:34:53
producing proton
00:34:57
and four
00:35:01
electrons again you're introducing this
00:35:04
new species this was there before so
00:35:06
you're introducing the species in
00:35:11
water and this would be basically
00:35:13
chapter
00:35:22
4 so that's the whole course
00:35:24
then um all it always
00:35:28
consider Assumption of
00:35:30
equilibrium speciation is very important
00:35:33
so understanding species different or
00:35:36
unique entities and how they're related
00:35:40
in each chapter we talk about the fact
00:35:41
how they're related and what potential
00:35:43
reactions we might
00:35:45
have pretty
00:35:47
straightforward um some additional
00:35:49
useful terms that we use here and there
00:35:53
but not as as common as the say
00:35:56
speciation is something something like
00:35:58
total dissolve solids TDS if you're
00:36:00
environmental engineering or chemical
00:36:02
engineer major when you look at a body
00:36:04
of water that's one of the features that
00:36:06
is always there what's the TDS and
00:36:09
that's basically how much ions you have
00:36:12
in that water the way they measure it is
00:36:15
they just evaporate that
00:36:17
water left with some salt and then that
00:36:19
value is basically the total dissolve
00:36:22
solid so no matter what is there it's
00:36:25
basically the total Math for example or
00:36:27
if you have sea
00:36:29
water and if you evaporate all of it you
00:36:33
roughly
00:36:34
get 30 gram or 30,000 milligrams for one
00:36:39
liter of water that could be sodium
00:36:42
calcium magnesium all of them it's
00:36:44
that's why it's total dissolved
00:36:46
solids um it it to some extent it
00:36:49
indicates how
00:36:51
much charge or how much ions you have in
00:36:54
that water but it's not very specific
00:36:57
uh the other factor is ionic strength
00:37:00
we're going to use that a lot uh it's
00:37:03
basically a measure of concentration of
00:37:05
ion so it's not necessarily the
00:37:09
concentration itself but also consider
00:37:13
what kind of volence you have so for
00:37:15
example if you have sodium chloride one
00:37:19
molar in terms of the concentration it
00:37:21
would assuming activity is equal to
00:37:23
concentration it would be equal to one
00:37:25
mole of sodium sulfate
00:37:28
but then the ionic strength of these two
00:37:31
are different so ionic strength is
00:37:33
taking into account what kind of charge
00:37:35
you're
00:37:36
ining or mathematically speaking I is
00:37:39
basically half of the overall
00:37:42
concentration times the
00:37:45
charge to the power of two this is
00:37:47
basically the
00:37:50
charge and this is the concentration
00:38:00
so sometimes we correct some of the
00:38:03
calculation using ionic strength just a
00:38:06
very uh simple example if we have for
00:38:09
example one mole
00:38:11
of sodium
00:38:15
sulfate then we know if it fully
00:38:17
dissociates
00:38:19
if then we get the concentration of
00:38:23
sodium it would be two times the total
00:38:26
concentration for one mole of sodium
00:38:28
sulfate we're getting two moles of
00:38:30
sodium so this would
00:38:34
be2 the concentration of sulfate would
00:38:37
be 1 to one so this would be .1
00:38:41
molar we know Z for
00:38:46
sodium is equal to + one it's the charge
00:38:49
is + one the charge for
00:38:54
sulfate is min-2 so so if we combine
00:38:58
these two information together then the
00:39:01
ionic strength would be half of the
00:39:04
concentration of sodium 2 * the charge
00:39:08
to the power of two time the
00:39:10
concentration of sulfate
00:39:12
times the charge to the power of
00:39:16
two then it would
00:39:18
be3 molar
00:39:34
so the concentration was
00:39:36
0.1 the ionic strength
00:39:39
is3 if it was the same concentration of
00:39:42
sodium choride then the ionic strength
00:39:45
think would be
00:39:46
0.1
00:39:48
so we're distinguishing between the two
00:39:51
Salt by doing this correction and
00:39:53
defining this terminology which is
00:39:56
rank uh you're going to see that in the
00:39:58
next
00:39:59
lecture more and more for Ionic
00:40:05
strength the the last one is basically
00:40:08
the hardness factor
00:40:10
for um a body of water you can always
00:40:13
Define oh this is a soft water this is a
00:40:15
hard water um generally speaking it's
00:40:19
talking about the concentration of
00:40:22
calcium magnesium and iron but more
00:40:25
specifically it's talking about the
00:40:26
concentration of all the
00:40:28
multivalent which their charge is more
00:40:31
than plus
00:40:32
one and but because mostly we have these
00:40:35
three ions or calcium and magnesium
00:40:38
often it's fair to say it relates to the
00:40:41
concentration of calcium and magnesium
00:40:43
so and based on that we could have we
00:40:46
could Define these
00:40:48
thresholds to talk about how soft or how
00:40:52
hard the water is less than 50 migr per
00:40:55
liter calcium carbon
00:40:57
equivalent it would be considered the
00:41:00
soft um water to some extent is also
00:41:04
talking about the total concentration of
00:41:06
ion in the system not necessarily but
00:41:09
specifically towards calcium and
00:41:11
magnesium but it could be a good
00:41:13
indication so when we look at the cities
00:41:16
in Texas
00:41:20
um where do you see like in the state
00:41:24
that have the highest hardness
00:41:30
so we can assume it's
00:41:31
related somehow related to the
00:41:34
concentration of ion which is coming
00:41:36
from
00:41:41
somewhere you see more in urban
00:41:44
area Industrial
00:41:46
Area specific industrial
00:41:52
area so when you produce oil you produce
00:41:56
a lot of produc water they contain tons
00:41:59
of iron specifically calcium magnesium
00:42:02
sodium lithium
00:42:04
also and it's possible they're like
00:42:07
exposed to an ACO fire or anything
00:42:10
related to that water that we're
00:42:12
providing for the city so it's fair to
00:42:15
say um if this is an industrial area
00:42:18
specifically for oil and gas we're
00:42:20
expecting more ions so the water is
00:42:24
harder in that area and specific
00:42:27
specifically when we look at the West
00:42:28
Texas like Midland which is sort of like
00:42:31
you see those fancy oil rigs and
00:42:34
everywhere um
00:42:36
Midland their
00:42:39
water is very very
00:42:44
hard it's roughly
00:42:47
500 milligram per liter
00:42:57
uh one other example here is for a hard
00:43:00
water is
00:43:03
Galveston uh you know Galveston is an
00:43:05
industrial Port so the risk of exposure
00:43:09
of those ions or like contamination with
00:43:12
those ions is pretty high and no
00:43:19
surprise uh I'm not sure if this is
00:43:22
because of political reason that Austin
00:43:24
is the capital or is far away from the
00:43:26
indust Ral
00:43:29
um segment of the state Austin
00:43:33
is somewhere here
00:43:47
85 and soft
00:43:51
example we're looking for place that is
00:43:55
not next to an industrial
00:43:58
area somewhere that it's um sort of a
00:44:02
college town they take they take good
00:44:04
care of their water system any example
00:44:08
comes to your mind near
00:44:09
Houston yeah exactly so that's basically
00:44:12
eight
00:44:24
so one city is missing
00:44:35
where do you see Houston in this
00:44:37
table considering what we talked
00:44:43
about close to Galveston is fair so it's
00:44:46
a very industrial City Oil and Gas not
00:44:50
expecting to be the best uh but
00:44:53
surprisingly it's um near Austin so this
00:45:00
is uh 135 on the edge
00:45:05
but not
00:45:07
bad and in general the average for
00:45:15
Texas is basically
00:45:19
200 milligram per
00:45:25
liter and the that's basically
00:45:29
sick hardest
00:45:33
water in the in the
00:45:36
country no surprise this is an
00:45:38
industrial State the regulation might be
00:45:41
also a
00:45:43
factor
00:45:44
that it's
00:45:47
not
00:45:48
pushing more in terms of reducing that
00:45:52
because it's a softening water is by
00:45:54
itself is a line of research some
00:45:57
classic U filters that you've seen
00:46:00
probably just to get rid of the calcium
00:46:03
and
00:46:05
magism so uh to wrap up what we talked
00:46:09
about basically we evaluated some of the
00:46:11
basics of water chemistry we highlighted
00:46:13
the fact that it's all the inter uh
00:46:17
interactions are centers
00:46:19
around uh this water so that's why we
00:46:22
we're all focusing in water
00:46:24
chemistry uh we talked about water
00:46:27
molecule itself the unique feature of
00:46:29
this dipole or being a polar molecule
00:46:32
that attracts tons of different
00:46:35
species and then this species can
00:46:39
further uh introduce uh more and more
00:46:42
species into
00:46:44
water any
00:46:49
question so again as I mentioned these
00:46:52
are the relevant readings if you want to
00:46:54
dig deeper uh it was M mainly from this
00:46:57
book the main reference of the book but
00:46:59
some also some interesting information
00:47:01
about water specifically in this lecture
00:47:04
and in the next lecture we're going to
00:47:05
talk about concentration and then
00:47:08
effective concentration which is the
00:47:10
activity
