Question

Fill in the blanks-
______________ (Molarity/Molality) of a solution is expressed as mol/lit.

Answer 1

Hint: It is the number of moles of solute dissolved in one litre of solution and it is simply termed as “M”. We can also obtain the mass of solute by multiplying the density by the volume.

Complete step by step solution:
Although there are several ways in which the concentration of a solution can be quantified, molarity is one of the most basic and widely used.
Molarity (M) is defined as the number of moles of solute dissolved in one liter of solution. The higher the molarity, the more concentrated or strong the solution is. For example, a 12M solution of HCl (i.e. hydrochloric acid) is much more concentrated than a 0.10 M solution. The basic formula for calculating molarity is:
Molarity (M) = moles of solute (mol) per liters of solution (L)
To solve for moles of solute, we can use algebra to manipulate the above equation producing the following derived formulas:
\[\text{Molarity=}\dfrac{\text{Moles of solute (mol)}}{\text{Volume per liter of solution (L)}}\] , where, moles of solute (mol) =$\dfrac{\text{Weight of solute}}{\text{Molecular Weight of solute}}$
A molality is the number of moles of solute dissolved in one kilogram of solvent. The molal unit is not used nearly as frequently as the molar unit and is used in thermodynamic calculations where a temperature independent unit of concentration is needed.
Therefore, the correct answer would be-
Molarity of a solution is expressed as mol/lit.

Note: Molarity is temperature dependent as it is defined as the number of the moles of the solute dissolved per liter of the solution. As volume is temperature dependent, its value changes with change in temperature. Accordingly, the molarity of the solution can also change. Also, Molality is not temperature dependent as it is defined as the number of the moles of the solute dissolved per kg of the solvent. As mass is not temperature dependent, its value does not change with change in temperature.