Question

Define the following :
i.) Henry’s law
ii.) Normality

Answer 1

Hint: The Henry’s law tells about the relation between the partial pressure of a dissolved gas and the amount of gas dissolved in the solvent at state of equilibrium.
The Normality is defined as the number of gram equivalents that can be dissolved in one litre of the solution. It is a concentration term.

Complete step by step answer:
Let’s see both the points one by one.
i.) Henry’s law
This law states that the mass of a dissolved gas in a given volume of solvent at equilibrium is proportional to the partial pressure of the gas above the liquid.
Mathematically, it can be written as -
P $ \propto $ C
Or P = ${K_H}$ C
Where ${K_H}$ is the constant called Henry’s law constant
P is the partial pressure of gas in atmosphere
C is the concentration of gas dissolved in solvent
The Henry’s law constant depends on the following factors :-
a.) On the nature of gas to be dissolved
b.) On the nature of solvent
c.) On the temperature and pressure

ii.) Normality
Normality tells us about the concentration of solution. It may be defined as the number of gram equivalents of solute divided by volume of solution in litres.
It can be written as-
Normality = $\dfrac{{Number{\text{ of gram equivalents of solute}}}}{{Volume{\text{ of solution (in L)}}}}$
Now, comes another term number of gram equivalents of solute. This can be defined as the mass of solute divided by equivalent mass of solute. The formula is written as -
Number of gram equivalents of solute = $\dfrac{{Mass{\text{ of solute}}}}{{Equivalent{\text{ mass of solute}}}}$
The Normality has units Normal (N) or $equ.{L^{ - 1}}$.
The normality equation has many applications. For ex- It is used to measure the number of ions that can be precipitated in precipitation reactions.
It can also be used in redox reactions to determine the number of electrons that can be donated or accepted by a reducing and oxidizing agent.

Note: Henry’s law has several limitations. It is applicable only when the molecules of the system are in state of equilibrium. It is also not applicable when gases are placed under high pressure. Further, the gas and solution should not participate in chemical reactions with each other.
The equivalent mass in the normality equation can be calculated by dividing the molar mass with n- factor.
Equivalent mass = $\dfrac{{Molar{\text{ mass}}}}{{n - factor}}$