Question

Why are `"molality"`, and `"mass percent"` SOMETIMES used in preference to `"molarity"`?

Answer 1

Because both `"amount of substance"` and `"mass"` are independent of temperature..........

Explanation:

`"Molality"="Moles of solute"/"Kilograms of solvent"`; both numerator and denominator do not vary with temperature.

`"Mole fraction"="Moles of one component"/"Total number of moles"`.

`"Mass %"="Mass of component element"/"Molar mass"xx100%`

And by the same token, consider the alternative, `"molarity"="moles of solute"/"volume of solution"`...

Now the numerator is invariant with temperature, but the denominator DOES vary with temperature. Of course, at so-called infinite dilution, `"molarity"`, and `"molality"` are essentially equivalent.