Volumetric Analysis and Quantitative Analysis
In analytical chemistry, the method of measuring chemical solutions, substances in the laboratory using specific apparatus is known as volumetry. This is very much essential for any chemistry experiments. The analysis of substances in chemistry is done by two major methods. (i) Qualitative Analysis and (ii) Quantitative Analysis. Quantitative analysis may be done either by volumetric analysis or by gravimetric analysis.
Qualitative Analysis: This involves in the detection of elements, radicals or functional groups. For example, after doing a number of tests which an inorganic compound we find out whether the given substance is a nitrate, chloride or carbonate and whether it contains the elements of metallic radicals like lead, mercury, copper or calcium if it is an organic compound whether it is an alcohol or phenol or an aldehyde or a ketone or acid.
Quantitative Analysis: This involves the estimation of the weight of substances. This is done in two ways:
(i) Volumetric Analysis: This involves a measurement of the volumes of solutions.
(ii) Gravimetric Analysis: This involves the conversion of a weighed amount of a given substance into another compound and determining the weight of the product.
Volumetric Analysis deals with (i) Acid : base (neutralization ) reactions, (ii) Oxidation –reduction (redox) reactions.
Examples for Acid –Base reactions
HCl, H2SO4, HNO 3, oxalic acid against NaOH, KOH, Na2CO3 etc.
Examples for Oxidation –Reduction reactions
KMnO4 against oxalic acid or Ferrous sulphate K2Cr2O7 against ferrous sulphate etc.
Explanation of terms used in Volumetric Analysis
Titration: It is the process of running one solution from a burette into a measured volume of another solution in a conical flask so as to find out the volume of the first solution required to interact completely with the second.
Indicator: It is the substance used to indicate the end point. The common indicators used in acid – base reactions are (a) methyl orange and (b) phenolphthalein. In redox titrations involving KMnO4, no indicator is used as KMnO4 itself acts as indicator. Potassium ferricyanide is used as external indicator in K2Cr2O7 titrations.
Methyl orange is yellow in alkaline solutions and red in acid medium. Phenolphthalein is pink in alkaline solutions and colorless in acid medium.
Standard Solution: A standard solution is a solution whose concentration or strength is known. For example, if 4 grams of pure anhydrous sodium carbonate are present in one liter of the solution, it is called standard solution.
Normal Solution: A normal (N) solution is a solution which contains one gram equivalent weight of the substance in one liter of the solution. For example, a normal solution of sodium hydroxide contains 40 grams of it dissolved in one liter. It is written as 1 N NaOH (40 g is the gram – equivalent weight of NaOH).
Normality: It is the ratio between the amount per liter and the equivalent weight of a solute. Normality = Weight per liter / Equivalent Weight.
This is a simple notes about volumetric analysis, quantitative analysis. If you want to read more on this topic please go through the links given above.