Write a note on isotonic solution.

Explanation

The solutions having the same osmotic pressure at a given
temperature are called isotonic solutiones.
Explanation : If two solutions of substances A and B contain `n_(A)`
and `n_(B)` moles dissolced in volume V (in `dm^(3)`) of the solutions, then their
concentrations are,
`C_(A)=(n_(A))/V "(in mol "dm^(-3))and C_(B)=(n_(B))/V "(in mol "dm^(-3))`
If the absolute temperature of both the solutions is T, then by
the van't Hoff equation,
`pi_(A) = C_(A)RT and pi_(B)=C_(B)RT,` where `pi_(A) and pi_(B)` are their osmotic
pressures.
For the isotonic solutions,
`pi_(A) = pi_(B)`
` therefore C_(A) = C_(B)`
`therefore (n_(A))/V= (n_(B))/V`
`therefore n_(A)=n_(B)`
Hence, equal voumes of the isotonic solutions at the same temperature will contain equal number of moles (hence, equal number
of molecules ) of the substances.
If the two solutions contain `W_(A)` gram and `W_(B)` gram of the
substances having molecular weights `M_(A) and M_(B)` then,
`n_(A)=(W_(A))/(M_(A))` moles and `n_(B)=(W_(B))/(M_(B))` moles.
Hence, for the isotonic solutions, `(W_(A))/(M_(A))=(W_(B))/(M_(B))`.
This relation can be used to determine the molecular masses of the
substances.