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Witzgall Chemistry: Heat of Solution Lab | MrWitzgall | YouTubeToText
YouTube Transcript: Witzgall Chemistry: Heat of Solution Lab
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this is the heat of solution lab where
we're going to find the heat of solution
of two different salts uh we're going to
be working with sodium hydroxide and
potassium chloride today two different
ionic compounds and we're going to be
determining their heat of solution which
is how much energy is released or
absorbed uh as they dissolve in water
we're going to use a simple calimer
today just going to be an insulated
coffee cup and we're going to start with
75 m
of room temperature water so we have 75
mL of water which is 75 G of water and
we're going to find the initial
temperature of the water in our
calorimeter so we're using our digital thermometer
thermometer
here and we'll find the initial
temperature of the water looks like 21.4
de C is the initial temperature of the
water what we're going to do now is
dissolve some salt in the water we'll
start with the sodium hydroxide so I'll
hydroxide and I'm weighing it on my
electronic balance here I have 6.28 G of
sodium hydroxide 6.28 G of sodium
hydroxide so it's an ionic compound it
looks like that it's a solid right now
and as it dissolves in water many ionic
solids uh either absorb heat or give off
heat as they dissolve in water so we're
going to take our sodium hydroxide pour
it into our water and we'll
stir and we'll see as it dissolves how
the temperature of the water is affected
and you can see right now that the
temperature of the water is going up
hasn't completely dissolved yet you can
see there's still number of solid pieces
of sodium
hydroxide in our calimer we're going to
keep stirring
until the sodium hydroxide has
completely dissolved and until the
temperature of the water has stopped
changing we can see that the temperature
is going up quite a bit so we can say
that this is an exothermic reaction the
heat of solution of sodium hydroxide is
giving off heat and therefore making the water
water
hotter it's continuing to dissolve just
stirring it to help it dissolve a little
bit more
quickly and the temperature complet
continues to go
up because heat is being
released as the sodium hydroxide dissolves
dissolves
we're going to be able to figure out how
much heat was released using the
equation Q is equal to delta T * Mass *
specific heat we know the specific heat
of water is
4.184 Jew per G de C and we can assume
that the specific heat of this solution
is about the same of as
water and it looks like we've reached
the maximum temperature
here just about it's almost done
dissolving see a few more solids in there
it's completely dissolved and we have a
final temperature of
40.4 so you can use the final
temperature and the initial temperature
to find the temperature change we know
the mass of water was 75 G cuz it was 75
M of water and we know the specific heat
of water
4.184 Jew per G de C you can use this
equation to figure out how much heat the
sodium hyd oxide released all that heat
was absorbed by the water and then you
can divide by the mass of sodium
hydroxide that was used uh and we can
convert that into moles so that we have
KJ of heat released per mole this is an exothermic
exothermic
reaction all right we're going to try it
again now with a different salt so we'll
set that kimer aside we'll get a new one
over here we'll take 75 mL of room
temperature water again according to our
we'll find the initial temperature of this
water and this time we're going to be
using a different salt we're going to be
using potassium chloride this time
potassium chloride for our second
trial uh I'll measure out a sample of potassium
potassium [Music]
chloride uh so the the initial
temperature of our water is going to be
21.3 de C this is just room temperature
tap water again 75 mL just like in our
first trial and this time we have a
different salt this time we have
potassium chloride and our starting Mass
here is 5.98 G of potassium chloride all
right just like I did before I'll take
the potassium chloride and dissolve it
in the
water we'll stir and as this salt is
dissolving in water we see again the
temperature of water is changing however
this time temperature of water is
decreasing so this is an endothermic
reaction as the potassium chloride
dissolves in water it absorbs heat from
the water it takes heat away from the
water therefore making the water
colder this is an endothermic
reaction and so we're going to stir
until it completely
dissolves and we get a final temperature
looks like it's completely dissolved and
it looks like 16.3 was the final
temperature of the water 16.3 was the
final temperature of the water that's
the coldest temperature that the water
got so this time the temperature change
of the water is negative because the
temperature decreased so when you figure
out using the equation Q is equal to
delta T * Mass * specific heat you'll
use a negative temperature change for
the water because the water got colder
uh since the water got colder it means
means that the reaction must have been
absorbing heat so Delta h of the
number and you have all the information
you need to do the calculations to find
the heat of solution of sodium hydroxide
which was
exothermic and the heat of solution of
potassium chloride which was endothermic
so two salts dissolved in water one
absorbed heat from the water One
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