Question

How can I calculate the moles of solute?

Answer 1

Hint: One mole of substance is equal to the value of the Avogadro constant $\left( {{N}_{A}} \right)$, which is $6.022\times {{10}^{23}}$ particles. Molecular mass is the sum of the mass of each atom present in the compound.

Complete step by step answer:
So in the question, it is asked how can we calculate the moles of solute. We know that the question is not too specific so let’s discuss various parameters by which we could find the equation for calculating the number of moles of solute.
Before going to the solution part and discussing the equation that gives us the value of the number of moles of solute. Let’s first check out what does solute means since we are dealing about the solute in the question.
The solution typically consists of two components i.e. the solvent and the solute.
The solvent is the term that represents the medium in which any given substance is dissolved whereas a solute is the term referred to the substance that gets dissolved in the liquid phase. We generally have solutions which have the solvent in the liquid phase and solute in solid phase but other solutions are also present in which the solute and the solvent are in different phases.
So now let’s see what is one mole?
One mole is that mass of substance which is equal to $6.022\times {{10}^{23}}$ particles which is also called the Avogadro constant.
And we could find the number of particles present in the number of moles and vice versa.
If in the question, that is of concern is provided with the mass of the substance i.e. solute taken and the molecular mass or molar mass is also given, then we could calculate the number moles as,
$\text{No}\text{.of moles of solute=}\dfrac{\text{Given}\,\text{mass}\,\text{of}\,\text{the}\,\text{solute}}{\text{Molecular}\,\text{mass}\,\text{of}\,\text{the}\,\text{solute}}$
And the unit of number of moles is mol.

Note: If we have the molarity of the solution and the volume of the solution in litre then we could find the number of moles of solute by rearranging the equation of molarity.
The equation of molarity is:
$\text{Molarity=}\dfrac{\text{number}\,\text{of}\,\text{moles}\,\text{of}\,\text{solute}}{\text{Volume}\,\text{of}\,\text{solution}\,\text{in}\,\text{liters}}$
Rearrange the equation for number of moles of solute and the equation becomes,
$\text{Number}\,\text{of}\,\text{moles}\,\text{of}\,\text{solute=Molarity }\!\!\times\!\!\text{ Volume}\,\text{of solution in liters}$
Similarly we can find the number of moles of solute if molality is given and the mass of solvent in Kg is given
$\text{Molality=}\dfrac{\text{moles}\,\text{of}\,\text{solute}}{\text{Mass}\,\text{of}\,\text{solvent}\,\text{in}\,\text{kg}}$
Rearrange the equation,
$\text{Moles of solute=Molality }\!\!\times\!\!\text{ Mass of solvent in Kg}$