Question

in 1 kg of given compounds how many moles are present

Answer 1

Answer:
10
3
⋅
N
A
Explanation:
The idea here is that
1 kg-mole
is equal to
10
3
moles.
This is the case because a mole of a substance must contain a number of particles of that substance equal to the number of atoms present in exactly
12 g
of carbon-12.
In this regard, you'll sometimes see a mole being referred to as a gram-mole,
g-mole
, just because it represents the number of particles equal to the number of atoms present in
12 g
of carbon-12.
Since you know that
1 kg
=
10
3
.
g
you can say that
1 kg-mole
=
10
3
.
g-mole
In other words, in order to have
1 kg-mole
of a given substance, you need to have the same number of particles of that substance as you would have in
10
3

g-moles
, or
10
3
moles, of that substance.
As you know, the number of atoms present in
12 g
of carbon-12 is given by Avogadro's constant,
N
A
N
A
=
6.022
⋅
10
23
.
particles mol
−
1
Since you have
1 mole
=
6.022
⋅
10
23
.
particles
you can say that
1 kg-mole
=
10
3
⋅
6.022
⋅
10
23
.
particles
1 kg-mole
=
6.022
⋅
10
26
.
particles
1 kg-mole
=
10
3
⋅
N
A
Keep in mind that this represents the number of atoms present in exactly
12 kg
of carbon-12.