The concentrations of solutions can be expressed in number of ways; viz : mass fraction of solute (or mass percent), Molar concentration (Molarity) and Molal concentration (molality). These terms are known as concentration terms and also they are related with each other $i . e .,$ knowing one concentration term for the solution, we can find other concentration terms also. The definition of different concentration terms are given below:

Molarity : It is number of moles of solute present in one litre of the solution.

Molality: It is the number of moles of solute present in on kg of the solvent.

Mole Fraction = $\frac{M o l e s o f a s o l u t e}{M o l e s o f s o l u t e (a l l) + M o l e s o f s o l v e n t}$

If molality of the solution is given as a, then mole fraction of the solute can be calculated by

$M o l e f r a c t i o n = \frac{a}{a + \frac{1000}{M_{s o l v e n t}}} = \frac{a x M_{s o l v e n t}}{a x M_{s o l v e n t} + 1000}$
where a = molality and M_solvent = Molar mass of solvent.

We can change : Mole fraction $\leftrightarrow$ Molality $\leftrightarrow$ Molarity

78 g of NaCl is dissolved in 242 gram of water. What is the mole fraction of the solute?

Question

Important Questions on Some Basic Concepts of Chemistry