What is a molar solution and how to calculate the molarity of a given solution?

 Molar solution:

The solution which contains one mole of a particular solute dissolved per one dm3 of solution at a specific temperature is known as molar solution.

Molarity:

The number of moles of a solute dissolved per dm3 of the solution is known as molarity of that solution. For example, one molar solution of sodium chloride (NaCl) is formed by adding 58.44 grams of NaCl into water and making the total volume of the solution upto 1 dm3. As 58.44 is the weight of one mole of NaCl and one mole is equal to gram equivalent weight of a substance. Thus, weight of sodium (Na) and chlorine (Cl) is added to calculate the weight of one mole of sodium chloride. The amount of solvent is different in solutions of divergent molarity because one mole of each substance possesses specific gram equivalent weight and the grams of solute added into solvent are different thus, the amount of solvent also differs for each substance while making the total volume of the solution upto 1 dm3. Equation 1 is used to calculate the molarity of a solution.

Using equation one molarity of a solution can be calculated if mass of solute is given. As number of moles of solute is equal to the mass of solute divided by molar mass of solute, thus equation 1 can be modified as written in equation 2.

Equation 2 can also be written in simplified form as follows


If the number of moles of solute are given than equation 2 or 3 is used to calculate the molarity of a solution. If the volume is given in cm3 it is first converted into dm3 by dividing the value in cm3 with 1000.

AS,

1 dm3 = 1000 cm3

Equations 1 and 2 are also used to calculate the mass of solute and number of moles of solute respectively if the molarity of a solution is given. The volume of solution is considered as one dm3 if the volume is not mentioned and only molarity of the solution is given or asked to prepare a solution of specific molarity. 




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