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

May 22, 2017

Because both $\text{amount of substance}$ and $\text{mass}$ are independent of temperature..........

#### Explanation:

$\text{Molality"="Moles of solute"/"Kilograms of solvent}$; both numerator and denominator do not vary with temperature.

$\text{Mole fraction"="Moles of one component"/"Total number of moles}$.

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

And by the same token, consider the alternative, $\text{molarity"="moles of solute"/"volume of solution}$...

Now the numerator is invariant with temperature, but the denominator DOES vary with temperature. Of course, at so-called infinite dilution, $\text{molarity}$, and $\text{molality}$ are essentially equivalent.