Molar concentration is the amount of solute dissolved in a unit volume of solvent. Through this article we will know how to calculate molar concentration and what molar concentration is. Molar concentration is also called as molarity. A large number of chemical compounds are made by dissolving a certain amount of compound in a solvent. The number of solute or the compound in one liter of the solution is called the molar concentration.
A solution is defined as the homogenous mixture of two or more components. The substance that is present in smaller concentration is called solute and the one which is present in larger concentration in a solution is called the solvent.
The equation for calculating molar concentration can be represented as,
In the above formula,
- cX is the molar concentration of the solute X
- nX is the amount of X
- Vsoln is the volume of solution in which the solute is dissolved
Calculating molar concentration
Suppose we want to find out the molar concentration of 140 g of sodium perchlorate i.e. NaClO4 dissolved in 450 ml of distilled water.
- Step 1: Your first step is to identify the solute and solvent in the solution. From the previous information we know that NaClO4 is the solute and distilled water is the solvent.
- Step 2: From the periodic table, estimate atomic weights of the elements that are dissolved in the solvent. From the periodic table we can find out that the atomic weight of Na is 23, Cl is 35.5 and O is 16.
- Step 3: Add these atomic weights to find out molecular mass of the solute.
Molecular mass = 23 + 35.5 +16 × 4
Molecular mass = 122.5 g/mole
- Step 4: Divide the mass of the solute dissolved in the solvent by the molecular mass of the solute. This is the number of moles of the solute.
Number of moles of solute = nX = 140/122.5
Number of moles of solute = nX = 1.14 moles
- Step 5: To convert the volume of solvent in the compatible units i.e. to convert it from ml to L, divide the volume of solvent by 1,000.
Volume of solvent = Vsoln = 450/1000
Volume of solvent = Vsoln = 0.45 L
- Step 6: Now, place the computed values of number of moles of solute and the volume of solvent in the above formula to calculate molar concentration.
Therefore,
CX = 1.14 moles/0.45 L
CX = 2.53 M
Therefore, the molar concentration of the solution is 2.53 M, i.e. the concentration of NaClO4 within a unit volume of distilled water is 2.53 M.
You can also place the formula and concentrations of solute and solvent in the online calculators to calculate the molar concentration of the solution online.
You can practice the following two examples following the steps explained above to gain perfection.
- 0.66 g of ethanol (C2H6O) is dissolved in 100 mL of blood. Find the molar concentration of solution. ( Using this the legal limit of blood alcohol concentration is decided)
- 60 g of NaOH is dissolved in 600 mL of water. Find the molar concentration.
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