What is Noramality, Molarity and Molality?

There are simple easy step to calculate Normality, Molarity and Molality.

It is easily explained in below video. 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

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)

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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 = 40

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.

Now Molality

So when 1 gm mole solute dissolved in 1 Kg solvent it’s called 1 molal or 1 m solution. Symbol for Molality is “m” Means final weight of solution may be more than 1 Kg.

Molality

No matter of volume involve in this case. Change in temperature will change the volume, so Molarity will change with temperature but Molality will remain constant with change in temperature, because it doesn’t have relation with volume.

Now Normality

So what is equivalent weight? Acidity or basicity is nothing but change in oxidation state or electron transfer during the reaction.

For NaOH = 40/1 = 40 equivalent gm

For HCl = 36.5/1 = 36.5 equivalent gm

For H2SO4 = 98/2 = 49 equivalent gm