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welcome to this online lecture for solutions. This is the part that won't be
covered in class
such as will be covered in your lab and also just
most this should be a review from q1 a and from your
your high school courses on solutions and different concentrations but
it's always good to have a nice view just go over a couple points from
this the slides chem 1b instructor
well covered this section 11 if your instructor isn't there
but he missed something I'm he can watch this video
ha so this concept I'm
from these size will be put into practice by doing study guide the
seven-member
all this work that you do a study guide be yes pure cane for lecture
yen for laughing quizzes and for your test so
make sure you understand what's going on and also as you do study guides A&B
and anything with that the lab course picture
you have no magic he answers and what I mean by magic answers
are questions that require some calculations
so I want tp make sure you show your work rather than just
magical number appearing on the page with shown where that number came from
to make she always show your work for your capitation how to set up the
calculations
so that I know that you understand what's going on
and you just did not copy that answer from your neighbor certainly look at
concentrations and solutions have variable compositions in a different
matter your saw you
with n GGAs solvent and to describe a solution
you need to describe the components have it and the relative amount so
what's in it and how much is there what's in it
and how much is it there
that's why concentrations are important and when we use the terms
dilute in concentrated so very qualitative terms
and so it's nice to have more quantitative descriptions of those
concentrations
the concentration is the amount that saw you in a given time and a solution to
make sure you remember those
those terms so you're so you'd answer your solution
and seem to have us all with you
that the concentrations Amanda saw you to give a man a solution
his with see something like this specially for lighting will a really
good
but occasionally them out if so use given
her amount to solve it will see this all week talk to molality
those are just some examples where those
definitions concentration differ slightly
for first with all the talk about is molarity summit where T is the most I've
saw you per liter of solution
this is used because it describes how many molecules of saw you
for each leader solution this is a very common you need a concentration the
chemist years
so for example the sugar solution contains
to you this tumour it has one leader
a solution and contains tools and sugar
now that so we have twice that body yet cheerleaders
with that two leaders is gone have formals but the ratio is always the same
so
42u 221b we reduce every issue
it's still a 122 ratio can just describe that mathematically
we can say that molarity is the most I've Saeed over the years absolution
notice when we use abbreviation for malaria d
that the big capital %um and this can be very important
for distinguishing between Moulana mole erlich Boller T
which is big capital %um and molality which is small capsule him
and when you do that by he had a scan be difficult it is
to distinguish between the two you you didn't seem to be very careful
when riding your big capital him from Larry and your small capital
your small %um from allowing so my lady in dissociation
and the molarity of an eye on a compound last determine the molarity have
dissolved
science some member we talk about ironic compounds
so like this calcium chloride which dissolves into solution it breaks up
into its audience
and so you have a calcium somehow seem to class I and
katayan and to you fluoride United's
to have a total of three irons
in solution for everyone calcium chloride now
if we look at this I'm the one molar calcium chloride solution
when dissolved boom do you
see meantime reading this correctly see one more workout in court contains one
more sarcastic or any solution
to getting very basic definition but because the castle court associates in
21
cast into place I'm the malaria the calcium two-plus
insulation is also one more cause notice it's a
one me change my pen
because it is a one 21
more ratio so when the captain coreg associates
to give one mole is also the only one more calcium
two-plus but when the calcium chloride
dissolves and you get the chloride ions that is a1
to to mole ratio so when the Castle Court Associate you give g2 chloride I
Ghanaians and so the chloride and I and
this to you know it's going to be twice that the calcium chloride
you have to take into account that factor so here's a
other I'm unit a concentration the molality
some who said the previous slide that morality
was lower case im and this is the most I've sawwy per kilogram of solvent
that's defined in terms of the solvent
not the solution like many other concentrations but the nice thing about
morality is that it does not vary with temperature
because it's based on the masses and not the volume so for instance
if you make a one molar
sugar solution and he put in refrigerator and you have a biometric
flask if you go in after the
solutions chill you notice that the water by Ines
lower in the no to know the solution was taken out
but the molality would be this saying because you still got the same ***
so member past solutions with changes in volume
based upon the temperature so you have very more verdi's
for the molality will not change that's why some people prefer
the unit a morality especially for
analytical purposes
no no you know the concentration is the person so it's the parts have saw you in
every
100 participants and the mass percentage by *** ***
Saeed than 100 participation by mass for example if a solution is .9 percent by
mass
their point nine grams saw you in every 100 grams a solution
or another way is to look at this point nine kilograms
simply so you in every 100 kilograms a solution
to the mass percent is a massive saw you in Graham's over the mass a solution in
grams
inner-city grams a chance that so that's where you can use kilograms in kilograms
songs as my hat Matthews cancel out
times a hundred percent now remember the masses
solution you need this for some other calculations
you will be study guide U-mass a useless is massive so you'd
less a massive the solvent and that will give your massive your solution
who gin looking at percent concentration percent is just the part over the whole
time to 100 percent
mass percent is a massive site
massive solution times i 100 percent
and sometimes you do the mass half-percent mass by volume
so that's a massive your song eating grams
over the volume a solution in Mills time two hundred
in this case the massive Saeed
plus the body with the song dokie qualifying the solution
so you have to be very carefully he just had the masses are you love are you
solve it
and get them find the solution concerns do not equal
and then is also buying percent which is a valueless are you over the volume of
solution
and you that both those in years and Nelson is a cute so each other out
time to 100 percent and if I'm the saw you place to find the solvent
doesn't necessarily equal the violence lesion so
volumes are not always additive with solutions yet to be very careful that
now it up but using concentrations as
conversion factors so concentrations show the relationship between them and
us are you and the amount of solvent
so we have a 12 percent and masked by mass
sugar a quiz solutions that means that
you have twelve grams of sugar in 100
graham's solution and when we have these
Civil Air bars like this this means exactly
are by definition so similar to the equal sign
it has a little bit more me or another way to look at this is 12 kilograms a
sugar
equals court yen
100 kilograms a solution 112 pounds
in hundred-pound a solution CPU various
units have mass eso and
so used to have that same ratio
now I 5.5 percent masked by volume
a silver in Berkeley means that they're 5.5
for him to sell over yen 100 males absolution
so that volume means the Weimar the solution
and that %um means the massive the song need
so them mass at the silver
nite 22 percent volume by volume
alcohol uniquely a solution means that there are 22
mills and ethanol in 100 miles
absolution
and a concentration to the me use Kimber between them out of saudi
into them out a solution or vice versa go back and forth
by using home the description the concentration as conversion factors
now this video
is I have actually online a blackboard already
to rather than in bed yet within this video I'm not going to do that
now when you watch this video
on mine owned by Ford I'm couple things that you should notice is that when the
read the volume you the finest to the meniscus the bottom the minister should
reach the slime
this important parts you react to solvent I'm site
measures so use and some other solvent
to get your compound to dissolve she can swirl it around
that he had a magnetic stir bar you who have excellent change the volume
T Adam your your solid in their where you saw you tune in
and yes we're solving just a Nazi have I've been
begins is all bits make your solution and would you get completely dissolved
I'm
wash any remaining I'm material
down the neck of the flask and I lose up to the mark so that the meniscus
his just the buy munis hisses at the line
on the by magic last and remember you always read the meniscus at eye level
so that's something he shouldn't
taking account pay a solution you need to know the amount a solution
and the concentration in the solution three-star you capture the masses are
you that you need
PC start with them out to the solution can use a conversion
use the concentration as a conversion packard news
so that they were five percent by mass that means that we won it five grams
I saw you her 100 grams a solution
so dissolve the Grahams us all you do not solve into total them out
absolution for example how would you compare 250
Graham grams I have a5 percent by mass click Close
solution
so were given that we have huh to one
cartoon fifty grand the solution but we will find
the massive the solution is to go into it and
our concentration that we want is a5 percent by mass that means we need five
grams of glucose
for every 100 grams a solution so you basically would take and grams a
solution is added to the grams of glucose
and by using be concentration
weekend make that conversion women apply our solution map
to start off with a 250 graham's and we use our concentration so
five grams of glucose for every 100 grams a solution
has mover that came from the concentration
so grams a solution can slap in grams a solution cancel out
that Lisa with you too glucose 250 times five divided by 100
just 12 with five grams of glucose
so to make this wish wishes of 0.5 grams that glucose
and where to put it in a flask and we're going to add enough water so the
and put it on a scale so that the total mass
is 250 grams so
what and water into the total mass is 250 grams
now and take a look at solution concentration in parts-per-million
says solution concentration using
ppm or parts for Amana parts-per-million this is the gramm society per one
million grams absolution
or another way of looking at this is milligrams of saw you her
1 kilogram solution so we've still got the same ratio or
one leader water per one kilogram wire
so for water solution we often approximate the kilogram solution
as the kilogram or one leader have water
bases guys one bill water equals
1 gram at room temperature throughout we have to make that
approximations to make math easier so parts know you
we can use the Grahams us all you need programs a solution
and multiply that by to to the six power
so begin with said look at
like this or the milligrams of sodium per kilogram solution
or milligram website her clear solution these are always to give that
parts-per-million so what by name
look example talk with you what my mother 2.5 percent mass
so the solution contains only .5 grams water
they give you the solution did steal 1.0 four grams per mount
so you know that you've got some he put five grams sugar
you want to find the the volume to our idea is to take the grams a saw you'd
then find the grams a solution
then find them now here's the solution and some the relationships that we can
use
is a hundred grand a solution was
2.5 grams sugar we get that from
are concentration or
another way of looking at that I'm 100 solution equals
1.04 graham's close tight-knit
the agency 10 absolutely was 1.4 grams
so if we start for my gramma Saeed
use our concentration we can convert to you grams a solution
and what we have our grams a solution we can then use that density
to get the mills a solutions that sir that's right
panic attack we're starting off their semi .5 grams sugar
multiplying and dime concentration
where the set me up with by conditioners in the denominator scissors
grams sugar the grams sugar cancel out
so now we're in grams a solution so take that
grams a solution most quiet by
the inverse the density so money do that so that that gramm's cancel out
now Randy volume has the solution which is in
and mills so we can answer 719
bills
show will use kids that we get the appropriate volume the units are correct
and magnitude seems reasonable
so we can talk of it though he answered this question
correctly know another unit
concentration is the mole fraction so
needed know the mole fraction for summer other calculations in Chapter 12 name of
action is to simply
the fractals a one-component the total
in the total moles about going to the solution the total almost
fractions and a solution have to equal one you have a number larger than 1 week
have all the parts remember without looking at the unit as one
and we're looking at the individual components and he'd have to be more than
one
and since it is a fraction that fraction is useless
now the more percentage is the person is a mold of one component do the total
moles at the court's decision such as simply the mall fraction
times a hundred percent and mole fraction a
a solicited the comp a we have
big X represent a small fraction
and a little a subscript represents what
component up the whole we're looking at so if great-looking with that means that
you can also complete a
over the total moles a solution that would be are more action
have a
his example 12.48 it's asking what's the molarity of a solution
prepared by mixing seventeen-point to gramm's
I have this organic compounds with .5 great kilograms have wanted to make
550 Mills have solution
to give into mass appear
compound the massive your water and the volume on the solution and we would have
fined
the molarity so if we have
the *** the compound we can get to the moles
we can use do that by using the the molar mass at the compound
if we have the mill so the solution week in
convert two leaders a solution just simply because is a thousand meals in
one leader
and then so once we have the moles at the compound over the
define the comp then we can get the the molarity
and so those relationships will help
in those commercial actors says we set up to solve it
we have 17 points you granzyme be
organic compounds the molar mass this
sixty 2.07 cram schools he'd need chocolate
calculate that from be I might not want to
this alone in this point 2771
moles I have a hard saw used and
we've just using that online at: 27 just to show
I'm keep up when I said fix that brick even more digits that we need just said
that we don't usually scrambling here
because 366 here 466 here
we should have 36 fixin are finally intercept this
underline other this 7 tells me anything after that somehow I need to get rid of
latex only
should have three significant figures
said now that I've got the moles cuz those grants cancel out
I can then take the volume in the session if after 50 mils
and convert that to you leaders
sawmills a cancel out
now I take my moles divided by my leaders
and mathematics yet point 538
and so I ran into that we have three significant figures that
36 pics here 36 pics here such as
366 semifinal answer okay so now it's want this
12 went for be as the last week from all their teeth now we're looking at
molality
so what is the molality have a solution prepared by mixing 1722
preamps with point five kilograms a white makeup 750 Mills absolution
so be very careful when you're reading this question
to make sure you don't accidentally misread molarity
more Mohali again given the mass
I have the saw you the massive the solvent
and the volume up this wishin and we want to find
the molality which is little %um so would begin with air start off with that
gramm's oversaw you'd
converted into molds used more mass we've got the
massive are solvent which is given and if we divide us too we should give the
molality throughout his moles up saw you purchase a gram
a solvent and no molar mass
this week after it former 62 107 grams per mole
so 70 points you grant us all you'd even divided by the molar mass
now give me your number malls the Crimson cancel out
and getting used to that 3 sick pigs
from also is keeping that exxon once we don't introduce round here
as we do for calculations with
within to get the morality we take the moles a
I saw you which would so just somehow found
divide that by the massive the solvent in kilograms
so .5 kilograms of water and our morality is .5
54 I'm morale
that big p.m. said: be a lower case
him
to a little time bow their my part
to the use correct in the magnitude this means muscling
coffin the way into that question correctly and going on to see
still same says the condition just different units
a concentration so this time to ask people with the percent by massive
solution
give the same thing but now we will find a person by mass
so well with a reduced a program to solve it
and then find the grams a solution
and then using the
Graham said they saw you to get the percent and to do some these
conversions we need to know that you there one thousand grams and one
kilogram
member
are percent by mass Instagram society
programs a solution times a hundred percent so we've got
.5 kilograms of water we're going to convert that
two grams of water I just by using their thousand grams per kilogram
this kilograms cancel out we need to Graham
and add are massive are solvent
so that 500 grams of water
and massive the song you so that 17 20 grams
I have I saw you said we add the
massive the saw you to solve it to the massive the solution
to notice that clearly significant to the ones place in this number
their significance have to be tense decimal place
so we can have these two numbers together we can only be
significant to the one's place we can be more
accurate then the one place I beat the halftime
to the desk move would not be significant so in this case we
have 36 fixed over keeping the point to you just been asked them to have round
two years
so to get the percent by mass we take massive our site you to the 17th which
graham's divided by the massive our solution
fam will play by 100 percent
and we get 3.33 percent
now
given same said condition just different concentrations to the mall fraction
lighted good example for how do these different concentrations
the one at the mall factions the solution
still feel the same amount we would find
X was in the mall fraction we take the
mass bar so you'd use the form the way to get to the malls
we take the massive our water use the form the way I wanted to get the malls a
water
and weekend use those to calculate
mole fraction memorable fraction
will be the malls them I saw you
heard them olza total everything
and we're going to use the more mass per site
still sixty 107 grams more and the more massive wires
18 not you grams per mole animal
there's a mole fraction definition
so again calculation them also have the SOL you'd
grams to cancel out
and here's our calculation for the moles of water take our mass the water was
with five kilograms convert from kilograms to grams
kilograms cancel out now that we're in it to grams of water
you take that more masked by that amo mas o that 1820
grams per mole grams will cancel out now give us
malls water the childrens kids that grams water can slap now God
more some water now to get our
mole fraction will take the moles ever saw you that with 2771
divided by our total malt balls everything said at that point 2771 more
society
plus the mall so far solvent art or moles so that's what we've done here so
this the malls are so you'd
over the total loss in its rules are so you'd
a small server solvent song or fraction
is 9389 times to minus third
and again with that more faction is unanimous
okay another example using sonar con tu
ahead conditions but now we're looking at the mall percent of the solution
given the same amount now we want to find
the mall percent so we take do the same calculations before
or just gone wild I have 100 percent some
same calculations still got the moles oversaw you too
and the malls over water you cancel out
thank you missing you this and this goes too fast
you you can always pause worry wind or anything like that considers recorded
to the same calculation before
the only difference now is that we most by the pad 100 percent to get to
the mall percent
I'm know when you're converting concentration years
asymmetry between him and a solution sonya given
percent I'm mastermind mass its
make sure life a lot easier if you just seem assume that you have
100 grams solution so that's a bet
fifty percent I mast mast solution
so for every 100 grams a solution that fifty grams
threaded you and see me get some weird number
because I V to just buy something that a hundred grams a solution
same thing is if you've got a given mask percent mass by volume said assume
100 knows a solution
so just by making these assumptions that show here
on the slide to make your your life and that he's here hoops
I'm also determine the amount a solution in non given
unit so it assume out a solution grams used in seat number two mills
and then two leaders or have assume the mass lesions
leader 10 used in city to convert to Graham's
also determine the amount of song in this administration
and gramm's and and moles
I'm also determine the amount of solvent
in some a solution and grams and moles
and use definitions to capture any other unions
now
doing these type calculations over and over again special EQL
study guide study guideby
you can start to see see the patterns
your brain is going to recognize what she more quickly but
am in beginning if you take a while and so you need to just keep trying to keep
working at it and
first time it right account you not do the right direction it's okay
take us peace a scratch paper try something else but
if you're having trouble figure out what to do this concept map that's actually
than in your book may help you figure out what to do so that's a
Amreeka time I saw you and you give the manholes
and you want to find the mass
you can use amo mas to compare between these
I industry do different ways that you can get to what she
what she said this is a concept map but
there's no good replacement process no claim
practice to remember
you know if the office hours email me there's tutors in the chemistry
department office
but make sure that you very comfortable with these types of
calculations in because you will be using the just for
can one be you'll be using those for other courses and even
I hear from some the biology professors uni understanding these units
concentration
you also important for them so it's not just press kit was that we need these
its from many different fields so
good luck and I hope this is helpful