Hello friends, I am Dr Nilesh Vala and today we are
going to learn difference between Normality, Molarity & Molality.
Many of us don’t have clear knowledge about it, and we find difficulties during real practice in lab and interview.
Many of us don’t have clear knowledge about it, and we find difficulties during real practice in lab and interview.
So without wasting your more time let’s start
learning…
Normality, Molarity & Molality are the units of
concentration. All three units express amount of solute dissolves in solvent.
First we will learn Molarity
As we know amount of
substance is also measured in gm-mole. (1 Mole = 6.022 x 1023)
So when 1 gm mole solute
dissolved in 1000 ml solution it’s called 1 molar or 1 M solution.
Symbol for Molarity is
“M”
So we can say that
Molarity is amount of solute in mole dissolved in 1 liter solution.
Be clear that final
volume of solution must be 1 liter.
Molarity = (weight of
solute in gram) / (Molecular weight of solute × Volume of solution in liter)
Suppose you want to
make 2 M NaOH 500 ml solution
For that you need
molecular weight of NaOH = 40 gm/mole
Volume of solution in
liter = 500 ml = 0.5 liter
2 = (required weight of
NaOH in gram) / (40 × 0.5)
Required weight of NaOH
in gram = 2 × 40 × 0.5
That means you have to
take 40 gm NaOH, dissolve it in minimum quantity of solvent then make up
solution to final volume of 500 ml, that’s your 2 M NaOH 500 ml solution.
