Question

Molarity is defined as:
A. The number of moles of solute dissolved in 1 $dm^3$ of the solution.
B. The number of moles of solute dissolved in 1 kg of the solvent
C. The number of moles of solute dissolved in 1 $dm^3$ of the solvent.
D. The number of moles of solute dissolved in 100 ml of the solvent.

Answer 1

Hint: Concentration of solution is the amount of solute present in a given amount of solution. The solution is a mixture of solute and solvent. The concentration of the solution is expressed in various units. Molarity is one of the units of concentration.

Complete step by step answer:
The concentration of the solution is expressed in various units like molarity, molality, normality etc.
Molarity of solution can be defined as the number of moles of solute dissolved in 1$dm^3$ of the solution
The molar concentration or molarity of the solution is denoted by the symbol M.
The mathematical equation of molarity is as follows:
\[{\text{Molarity = }}\dfrac{{{\text{number of moles of solute}}}}{{{\text{1 d}}{{\text{m}}^{\text{3}}}{\text{of the solution}}}}\]
a. The unit of molarity is M or \[{\text{mol/d}}{{\text{m}}^{\text{3}}}\]
So, the correct option is (A) the number of moles of solute dissolved in 1$dm^3$ of the solution.
b. The definition given in option B, the number of moles of solute dissolved in 1 kg of the solvent is the definition of molality. So, option B is incorrect.
c. In option C it is given, number of moles of solute dissolved in 1 $dm^3$ of the solvent. This is an incorrect definition of molarity as here it is considered 1 $dm^3$ of the solvent.
d. In option D it is given, the number of moles of solute dissolved in 100 ml of the solvent. This is an incorrect definition of molarity as here it is considered 100ml of the solvent.

Thus, the correct answer is option A.

Note:
The unit molarity is used to express the concentration of the solution. It indicates moles of solute dissolved in $dm^3$ of the solution. Different units are used to express the moles of solute dissolved in a given amount of solvent.