Phenolphthalein as Indicator Video Lecture | Science Class 7 (Old NCERT)

hello friends this video on acids bases
and salts Pat eight is brought to you by
exam four calm no more fear from exam so
now we are going to talk about the next
indicator which is not a naturally
occurring indicator but it is a chemical
compound but phenol cannon but this also
acts as an indicator so phenol thailand
this is how the structure of
phenylthaline looks like so if you
actually look at the structure you will
see that error twenty carbon atoms
fourteen hydrogen atoms and four oxygen
atoms so for oxygen you can very easily
see and wherever you have the corners
you have one carbon so four five six so
six five and here six carbon here six
carbon here so already eighteen carbons
here so you have one more here and one
more here so total 20 carbons and you
have fourteen hydrogen's connected to
these patterns so that's the chemical
formula of phenol Talan so it is a
chemical compound which is colorless and
it is highly soluble in water and that's
how you can prepare the venom and in
solution and then that solution can act
as an indicator it is also called as pH
pH because of it's such a big name so
sometimes it is quite difficult to do
such a big name so that is why your
short form has been introduced that is
called pH pH that is can all Talan
so basically pH is taken from here and
in another page from here so let's see
how do we prepare the phenylthaline
indicator so in that case we take some
when all values of an all failing is
actually obtained in the form of powder
so that powder form of an alkyne little
bit of powder is taken and then it is
mixed with ethanol solution so this is
how the phenylthaline powder looks like
so when i see some amount of you know a
thousand powder a very little amount as
little as 0.5 grams of an article and
powder should be enough and then it is
mixed with around 50 milliliter of
ethanol solution now what is eternal
solution ethanol solution is that
by the ethanol mixed with water so it
will have equal amount of ethanol and
equal amount of water 50 percent ethanol
and 50 percent water that forms the
internal solution
what is it or not Eterne is an alcohol
that the c2h5oh so this is how the
structure of ethanol looks like so you
take ethanol solution and then you add
0.5 grams of the North Island powder
into this solution so as a result what
you get you get a solution because as I
and if an alternate powder is highly
soluble in water so it mixes up very
nicely with this solution and as a
result we get the phenolphthalein
solution which acts as the
phenolphthalein indicator so now the
question is how do we perform the test
how do two solution reacts when it
encounters an acid or a base so this
turns the acetic solution colorless it
is colorless an acidic solution but it
turns pink in basic solutions so you see
again the difference in color only with
tell which one is an acid and which one
is a base so the extent of change in
color of phenol that helps us to decide
the acidity of a substance so these are
some of the indicators which are used to
decide which substances acetic and which
one is basic thank you please visit
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