A database about Preparation of Laboratory Reagents. A Project of SCIENCE Pakistan

Formulae for Reagent Preparation of Solid Compounds

To make a Molar Solution (mol.dm-3):

  • Molarity is the number of moles of solute dissolved in one liter of solution. The units, therefore are moles per liter, specifically it's moles of solute per liter of solution.
                                   molarity = moles of solute
                                                  liter of solution


FORMULA
                        Relative Molecular Mas (Mr) x Molarity x Volume (mL or cm3)
Amount:                                                                                                  
                                                                 1000


* put Mr of your desire compound
* in molarity put your desire molarity
* in volume put your desire volume

Note: After calculating the amount; dissolve this amount in distilled water OR any other solvent and transfer this solution to the Volumetric/Graduated flask and fill with distilled water OR any other solvent upto the mark.

To make a Normal Solution:

The normality of a solution is the gram equivalent weight of a solute per liter of solution. A gram equivalent weight or equivalent is a measure of the reactive capcity of a given chemical species (ion, molecule, etc.). Normality is the only concentration unit that is reaction dependent. Here's an example of how to calculate the normality of a solution.

Normality Example #1
1 M sulfuric acid (H2SO4) is 2 N for acid-base reactions because each mole of sulfuric acid provides 2 moles of H+ ions.
1 M sulfuric acid is 1 N for sulfate precipitation, since 1 mole of sulfuric acid provides 1 mole of sulfate ions.

Normality Example #2
36.5 grams of hydrochloric acid (HCl) is a 1 N (one normal) solution of HCl.
A normal is one gram equivalent of a solute per liter of solution. Since hydrochloric acid is a strong acid that dissociates completely in water, a 1 N solution of HCl would also be 1 N for H+ or Cl- ions for acid-base reactions.

FORMULA

                        Equivalent weight  x Normality x Volume (mL or cm3)

Amount:                                                                                          

                                                              1000

* Equivalent weight (also known as gram equivalent) is a term which has been used in several contexts in chemistry. In its most general usage, it is the mass of one equivalent, that is the mass of a given substance which will:
  • supply or react with one mole of hydrogen cations H+ in an acid–base reaction; or
  • supply or react with one mole of electrons e in a redox reaction.
Equivalent weight has the dimensions and units of mass, unlike atomic weight, which is dimensionless. Equivalent weights were originally determined by experiment, but (insofar as they are still used) are now derived from molar masses. Additionally, the equivalent weight of a compound can be calculated by dividing the molecular weight by the number of positive or negative electrical charges that result from the dissolution of the compound.

To Make a Percent Solution (%):

The best way to explain percent solutions is with a few examples. To make a 1% glucose solution, grab a 100 ml bottle, add 1 gram of glucose to your bottle and bring the volume up to 100 ml. To make a 1% NaCl solution, grab a 100 ml bottle, add 1 gram of NaCl to your bottle, and bring the volume up to 100 ml. To make a 3.75% glucose solution, grab a 100 ml bottle, add 3.75 grams of glucose to your bottle, and bring the volume up to 100 ml.

FORMULA:
                     
dry mass in grams 
% solution =                              x 100
volume in ml


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