Molarity Formula and Calculation

Molarity Formula With Example – Molarity Calculator

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What is Molarity?

Molarity means numbers of moles of solute per liter of solution.It is denoted by symbol M. Based on this defination the molarity formula becomes as below:

 Molarity(M) = Numbers of Moles of Solute(n) / Volume of Solution In Liter(L)———(1) 

To understand molarity concept first you need to know what is mole & How to calculate it.

 Mole = Weight of substance in gram / Molecular weight of the substance (gm/mol)——- (2) 

  1. Calculation of Numbers of Mole in Solution:

To calculate mole we take example of Sodium Hydroxide(NaOH). Suppose, we dissolve 40 gm of NaOH in one liter of solution then what is the numbers of mole present in this solution?

  • First, Calculate molecular weight of NaOH
  • Na=23 g/mol + O=16 g/mol + H=1g/mol=23+16+1=40 g/mol
  • In our example we dissolve 40 gm of NaOH in one liter water that means weight of substance becomes 40 gm

Let’s put above values in molarity formula (2),

 ♦ Mole = Weight of substance in gram / Molecular weight of the substance (gm/mol) 

Mole = 40/40 =1

Now, we have numbers of mole available with us & we also know the volume of solution so put both the values in formula(1),

 ♦ M = Moles of Solute(n)/ Volume of solution in liter(L) = 1/1 =1M 

In conclusion, simplest definition of molarity is when we dissolve substance exactly the same weight as its molecular weight in one liter of water then the molarity of the solution becomes 1M .

Let’s take another example,

How to calculate Molarity of concentrated HCl?

Three things requires in order to calculate molarity of concentrated solution in our case it is concentrated Hydrochloric Acid(HCl):

  1. Molecular Weight :    36.46 gm/mole
  2. Specific Gravity :        1.18
  3. Percentage of Purity : 35.4% (Convert into decimal divide it by 100. 35.4/100=0.354)

Please note that all of the above information you can find on packing lable of solution.

Important Note:
♦ Remember this molarity formula to calculate molarity of any commercially available liquid solution:
 M = Specific gravity × Percentage of purity × 1000 ÷ Molecular Weight 

Put above values in this formula;

M = 1.18 × 0.354 × 1000 ÷ 36.46 = 11.46 M

So,finally the molar concentration of concentrated solution is 11.46 M.

Molarity Calculator For Concentrated Liquid Chemical

Molarity Calculator is very handy tool for science student to make reagents for analysis. You can easily calculate molarity of any concentrated acid or base liquid solution.
All you need to do is only enter the three values which is mentioned on label of reagent bottle.

Hope, This article will clear your concept about molarity formula & its calculations.

 

 

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