Hang tight while we fetch the video data and transcripts. This only takes a moment.
Connecting to YouTube player…
Fetching transcript data…
We’ll display the transcript, summary, and all view options as soon as everything loads.
Next steps
Loading transcript tools…
Ch 9.3d Hess's law basic | General Chemistry | YouTubeToText
YouTube Transcript: Ch 9.3d Hess's law basic
Skip watching entire videos - get the full transcript, search for keywords, and copy with one click.
Share:
Video Transcript
Video Summary
Summary
Core Theme
Enthalpy's state function property allows for the calculation of reaction enthalpies by summing the enthalpies of stepwise reactions, as demonstrated by Hess's Law.
Mind Map
Click to expand
Click to explore the full interactive mind map • Zoom, pan, and navigate
so one of the advantages thinking about
our enthalpy as a state function is that
we can start to add things together uh
between the different reaction so that
concept is from hess's law and this is
totally due to the fact that it's a
state function for enthalpy so it the
process of enthalpies can be written as
a series of independent stepwise
reactions and the enthalpy change for
all of it is the sum of all the enthalpy
changes in all of the
reactions so here's an example of
thinking about hess's law so we want to
determine the enthalpy of formation of
iron Tri chloride so thinking about how
we want to calculate that and we are
given these two steps and what we can do
is we can do some sort of manipulations
of this so first of all we need to go
ahead and WR the reaction for the
formation of iron chloride so we know
that the enthalpy of formation for the
reaction is we are going to form one
mole of iron chloride and we are going
to form this from the elements at its
standard state so we know that we have
iron as a solid in here and we know
chlorine uh exists as a datomic gas but
how many chlorines do we actually need
so if we think about this we only need
three so if we think about our leish
structure looks something like this we
only need three out of the four so
that's three Hales of a
chlorine of chlorine
molecules so how do we actually
calculate this so this is now our Delta
H knot this is written as a formation we
are given these two fundamental steps um
uh up here so one and two what can we do
to actually manipulate them and add them
together and in this case it's actually
relatively straightforward we notice
that we have a product of fe2 over here
and we have one of them on this side of
the equation and lo and behold if we
take both of these equations and we just
add them up we see that we have an iron
on this side we have have an iron over
here we have one chloride plus a half of
a chloride this gives us our three Hales
chlorine and um our iron over here and
if we look on the product side if we add
this up this iron uh D chloride ends up
being canceled on both sides and we have
iron Tri chloride so for this we can
take our hess's law that our heat of
formation is going to be the sum of
these two over there and if we add up
the some of these we end up getting -3 99.5
99.5
K so that is the final answer for this
reaction so that is a fairly
straightforward kind of hess's law where
you can just kind of add it up the only
tricky part was go was writing this kind
of um enthalpy of formation and that was
just by the definition of what a
formation reaction actually
is and the next part is we will go
through something a little bit more complicated
Click on any text or timestamp to jump to that moment in the video
Share:
Most transcripts ready in under 5 seconds
One-Click Copy125+ LanguagesSearch ContentJump to Timestamps
Paste YouTube URL
Enter any YouTube video link to get the full transcript
Transcript Extraction Form
Most transcripts ready in under 5 seconds
Get Our Chrome Extension
Get transcripts instantly without leaving YouTube. Install our Chrome extension for one-click access to any video's transcript directly on the watch page.
