Question

Why concentration of pure liquid and solid is excluded?

Answer 1

concentration = n/v  (n= number of moles, v= volume)

n can be written as given mass (m) / mol. mass (M)

so,

=  (m/M) / v

= m/ M * v

but m/v = density

so,

concentration = d / M

For pure liquid and pure solid, density to mol. mass ratio is always contant. therefore the concentration is taken as '1'. and is thereby excluded.