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Volumetric Analysis

Mass Percentage:

-The mass percentage of a component in a given solution is the mass of the component per $100$ gm of the solution.

-For e.g. If $W_{A}$ is the mass of the component $A$ , $W_{B}$ is the mass of the component $B$ in a solution. Then, Mass percentage of $A$ in a solution = $\frac{W _{A}}{W _{A} + W _{B}} \times 100$

Volume Percentage:

-This unit is used in case of a liquid dissolved in another liquid.

-The volume percentage is defined as the volume of the solute per $100$ parts by volume of solution.

-For e.g. If $V_{A}$ is the volume of component A present is $V_{so l}$ volume of the solution. Then, Volume percentage of $A$ in the solution = $\frac{V _{A}}{V _{so l}} \times 100$

Strength of Solution:

-Strength of a solution is defined as the amount of the solute in gm, present in one litre of the solution.

-It is expressed as $g L^{- 1}$ .

-Mathematically,

$St re n g t h = \frac{M a ss o f so l u t e in g m}{V o l u m e o f so l . n in l i t res}$

Molarity:

Molarity of a solution is defined as the number of moles of solute dissolved per litre of solution.

Molarity is expressed by the symbol $M$ .

Mathematically,

$M o l a r i t y = \frac{N o . o f m o l es o f so l u t e}{V o l u m e o f so l u t i o n in l i t res}$

Or,

$M o l a r i t y = \frac{wt . o f so l u t e ( in g m )}{m o l ma ss} \times \frac{1000}{V}$

It can also be expressed as,

$M o l a r i t y = \frac{St re n g t h in g m s p er l i t re}{M o l ec u l a r ma ss o f t h e so l u t e}$

Normality:

Normality of a solution is defined as the number of gram equivalents of a solute dissolved per litre of the given solution.

Normality is expressed by the symbol $N$ .

Mathematically,

$N or ma l i t y = \frac{N o . o f e q . o f so l u t e}{V o l u m e o f so l u t i o n in l i t res}$

Or,

$N or ma l i t y = \frac{wt . o f so l u t e ( in g m )}{e q . wt} \times \frac{1000}{V}$

It can also be expressed as,

$N or ma l i t y = \frac{s t re n g t h in g m s p er l i t re}{Eq . wt o f t h e so l u t e}$

Note:

$N or ma l i t y = M o l a r i t y \times \frac{M o l ec u l a r wt o f so l u t e}{Eq . wt o f so l u t e}$

Molality:

Molality of a solution is defined as the number of moles of solute dissolved in $1000 g m$ of a solvent.
Molality is expressed by the symbol $m$ .
Molality does not change with temperature.
Mathematically,

$M o l a r i t y = \frac{N u mb er o f m o l es so l u t e}{Eq . ma ss o f so l u t e}$

Formality:

It is the number of gram formula masses of solute dissolved per litre of the solution.
It is denoted by the symbol $F$ .
In case of ionic compounds like $K Cl, C a C O_{3}$ etc Formality is used in place of Molarity.
Mathematically,

$F or ma l i t y = \frac{N u mb er o f G r am f or m u l a ma sses o f so l u t e}{V o l u m e o f so l u t i o n in L i t res}$

Mole Fraction:

It is the ratio of number of moles of one component (solute or solvent) to the total number of moles of all the components (solute and solvent) present in the solution.
It is denoted by the symbol $X$ .
Let us suppose that a solution contains two components $A$ and $B$ and suppose that $n A$ moles of $A$ and $n B$ moles of $B$ are present in the solution then,

Mole fraction of $A$ ; $X_{A} = \frac{n A}{n A + n B} \dots\dots .. (i)$

Mole fraction of $B$ ; $X_{B} = \frac{n B}{n A + n B} \dots\dots .. (ii)$

Relationship on Volumetric Analysis:

1) Substance reacts by gm. equivalent:

-If substance $A$ reacts completely with $B$ then,

$n o . o f g m . e q u i v a l e n t o f A = n o . o f g m . e q u i v a l e n t o f B$

or, $(\frac{wt .}{Eq . wt})_{A} = (\frac{wt .}{Eq . wt})_{B}$ $(\frac{W}{E} = \frac{N \times V}{1000})$

2) For Acid Base Titration:

$V_{A} \times N_{A} = V_{B} \times N_{B}$

3) Dilution Formula:

$V_{1} S_{1} = V_{2} S_{2}$
$g m / l = N or ma l i t y \times Eq . wt = M o l a r i t y \times M o l . wt$

4) Mixing no. of acid or alkali solution:

Final Normality, $N = \frac{V _{1} N _{1} + V _{2} N _{2} + ... V _{n} N _{n}}{V _{1} + V _{2} + ... V _{n}}$

5) Mixing of acid solution with alkali solution:

If $(V * N)_{a c i d} = (V * N)_{ba se}$ , solution is neutral.
If $(V * N)_{a c i d} > (V * N)_{ba se}$ , solution is acidic.
If $(V * N)_{a c i d} < (V * N)_{ba se}$ , solution is basic.
For acid excess, final normality,

$N = \frac{V _{a} N _{a} - V _{b} N _{b}}{V _{a} + V _{b}}$ ; a= acid and b= base.

For base excess, final normality,

$N = \frac{V _{b} N _{b} - V _{a} N _{a}}{V _{a} + V _{b}}$ ; a= acid and b= base.