Mole and Equivalent Concept:-
In the beginning we will be targeting only the mole concept. And we will try to understand
only the mole concept. We will not bring into the discussion of equivalent concept, this will
be only done when we have completed the portion of mole concept. But both are parts of
Stoichiometry calculation, so there is no need to think much about it whether it is
independent or combined. They are combined, they are independent, you can say they are
both. So, there is no need to think about it much.
Again, we start off with the first and foremost very simple definition, mole concept. In mole
concept you will be actually doing the calculations. You will be, you know weighing a sample,
calculate mass or you will be counting that in this how many entities are there, maybe
molecules, maybe irons, maybe atoms, things like this you will be calculating. Okay, we will
do something like this. You know, mostly we are afraid of mole concepts, why, because
there are more calculations in it, and you feel that now we will have to do these dreadful
calculations and how will we do that. Remember, if you overcome the fear of calculations
then mole concept is very, very easy, nothing complicated, okay. There are many systematic
thought process questions, things are not as complicated as it looks. Yeah, the steps may
increase, maybe one problem would be solved in one step, maybe in two steps or maybe in
three steps. But the process is very easy in mole concept. Be comfortable, whoever knows
addition, subtraction, multiplication, division and unitary method, they know mole concept
also. If someone is unable to do these then they will have little problems. I have only one
request for them, the ones who have problems while doing calculations, improve your speed
on calculation and be confident with calculation. Otherwise mole concept is a very easy
chapter, okay.
Now, in this particular chapter we will start off with the definition of Atom. Yet again, we
start with the definition with atom, which we had discussed in atomic energy. So, tell me the
definition of atom. What is the definition of atom? It is the smallest indivisible particle of
matter. According to which theory, we will write here. You write the definition of it again.
Atom is the smallest part of an element, atom is the smallest part of an element, atom is a
smallest part of an element that can participate in a chemical reaction. Atom is a smallest
part of an element that can participate in a chemical reaction. When we are talking about
chemical reaction we say that there is one more type of reaction associated. There are two
types of reactions, one is a chemical reaction, the other is a radioactive reaction, okay.
Radioactive reaction is also called as Nuclear reactions, okay. So, what we say here is,
suppose I have a reaction here, HCL plus NaOH and they react, what will happen? Okay, here
identity of elements is maintained. Here one HCL is there, two H and one oxygen, similarly,
here one Na, one CL, two H and one oxygen. Similarly, if I take here, let’s say silver nitrate
plus NaCL, so what do I get, AgCL plus NaNO3, this is the example of double displacement
reaction. So when we see this sort of example, we call them as normal chemical reaction. In
which chemical identity of the element is preserved, it is not changed. Whereas in
radioactive reaction, let’s say we pick up uranium 92, the uranium atomic number is 92 and
its isotope, if considered particularly, it is 238. Let’s say it emits out an alpha particle, now
what is an alpha particle? Helium 2 positive nuclear, which we say helium 2 positive particle
is emitted. Whenever we write any radioactive reactions we never write the charges, we just
write the elements which are emitted from there. We say, suppose helium is emitted, in
helium there are two protons and two neutrons, agreed. If we say from this how many
protons are emitted from this uranium nucleas, 2 and how many left, 90 and what is the
reduction in mass number. 4 because 2 protons and 2 neutrons. So, I will write here, 230 and
if you remember this 90 stands for thorium, okay. So, uranium and thorium and with that
what was given out, so you told alpha particle was given out and you got the thorium, okay.
And suppose we say some energy was also emitted out. That is in the form of Gama
radiations, okay. Now, see this equation and compare it with this equation. Have the identity
of elements been preserved? The nucleus itself has changed, so we say that there are two
types of reactions. In which case we will say that atom is a smallest part which can
participate in a reaction, in a chemical reaction not in a radioactive reaction. In radioactive
reaction, all the atomic particles participate like alpha particles, neutrons, protons things like
these participate. So we have to differentiate between both of them.
I will give you one more example of reaction. Do you remember discovery of neutron. Yes, in
(6:53) and with what we have confirmed with, beryllium. With what we had bombard it,
alpha particle and what was made out of it, carbon and what was emitted. Again identity of
elements had changed. What had happened? This is also a nuclear reaction. We will mark it;
let us say beryllium 4, 9, helium 2, 4. Now you see, you try to conserve the mass number and
atomic number. 4 plus 2, 6 carbon. How much is 9 plus 4, 13 total mass number. But we say
isotope of carbon is made of 12 number and to conserve mass number what will be emitted,
neutrons. So these types of reactions are called as radioactive reactions. For us, where is the
atom in the whole concept, only in the case of chemical reactions. Only in these cases you
will call it to be the smallest part. It’s only in the case of chemical reaction, never in the case
of radioactive reactions or nuclear reaction. Did everybody understand this? So that is
important, so keep this in mind. From helium to, yeah, yeah, like that you can choose
anything. You can do many nuclear reactions. If you bombard on isotopes of beryllium you
will get some other elements. We are taking just couple of examples to understand what are
the examples of nuclear reactions. In one case, alpha is emitted and in another case alpha
has been absorbed. There are many types of examples. We have not talked about beta
particles, positron emission, electron emission. We are just taking simple analysis which is
not complicating our analysis. Everybody understood this thing, okay.
Now, if we talk about, we defined what is an atom. But we have to do calculations and to do
calculations, I have to count. There are two types of counting procedures, we can count as
discreet quantity. Let’s say you are students who are counting as discreet quantity. For
example we will start counting, 1,2,3,4,5,6,7,8,9,10, we count like this. This is one way.
Second I will collect information.