Numerical Problems in Organic Quantitative Analysis

Gravimetric analysis is a method for determining the quantitative composition of a chemical compound by generating a residue, then isolating, drying, and weighing the precipitate. The percentage of a specific ion or element in a sample is calculated using quantitative analysis in this scenario. A substance of unknown composition is dissolved in water to form a precipitate by letting the ion of interest to react with a counter ion in the process of quantitative analysis of organic compounds, for example. The precipitate is then isolated, dried, and weighed to calculate the mass of the ion of interest based on the percent mass composition of the precipitate.

General introduction to organic chemistry and organic compounds 

• Organic substances are unquestionably essential for the survival of life on Earth. They include complex molecules such as genetic information bearing deoxyribonucleic acid (or DNA) and proteins, which are key components of the human (or any biological creature) body’s blood, muscles, and skin.
• Clothing, fuels, polymers, colors, and pharmaceuticals all contain organic molecules. These are some of the most important areas in which organic molecules can be used.
• Fundamental principles like molecular structure and ionic mass aid in the prediction and comprehension of organic compound properties.
• Organic compound qualitative and quantitative analysis aids in comprehending the concept and attributes of organic compounds.
• Carbon, nitrogen, hydrogen, oxygen, sulfur (or sulfur), phosphorus, and halogens are all components of organic molecules.

 Qualitative and quantitative analysis of organic compounds

• The quantitative study of organic compounds entails dissolving an unknown chemical in water and enabling the ion of interest to react with a counterion to generate a precipitate. The precipitate is then isolated, dried, and weighed to determine the mass of the ion of interest using the percent mass composition of the precipitate.

• The species (i.e., the elements and ions) present in an organic compound are detected through qualitative analysis. The qualitative study of an organic compound focuses on “what is/are present” rather than “how much is/are present”.
• There are a number of tests that may be used to detect the presence of components and estimate the amount of each element present in the combination. There are two levels to the tests: preliminary and confirmed.

             The following are some of the tests:

• Carbon (C) and hydrogen (H) detection test: In a dry test tube, a substance is heated with CuO (i.e., Cupric Oxide) to detect the presence of carbon and hydrogen. If C and H are present, they are oxidized into CO2 and H2O gasses, respectively. The presence of CO2 and therefore of C is proven if the gas turns lime water milky, while the presence of H is confirmed if H2O changes the color of anhydrous CuSO4 to blue.
• Phosphorus (P) is detected by heating an unknown organic chemical in the presence of an oxidizing agent, which converts phosphorus to phosphate.
• This solution is then heated with strong Nitric acid and treated with ammonium molybdate, and the presence of phosphorus is confirmed if a yellow precipitate forms. The following is the reaction:

Na3PO4 + 3HNO3 -> H3PO4 + 3NaNO3

H3PO4 + 12(NH4)2MoO4 + 21HNO3 -> (NH4)3PO4.12MoO3 + 21NH4NO3 + 12H2O

• For estimating the amount of Carbon (C) and Hydrogen (H), Liebig’s Combustion method is used (H).
• Estimating the quantity of halogens in organic compounds using the Carius method.

• The Dumas and Kjeldahl methods are used to calculate the quantity of nitrogen (N) in an organic compound.

• Sulfur (S) and Phosphorus (P) concentrations in organic compounds are calculated.
• Aluise’s method for calculating the amount of oxygen (O) in an organic molecule.
• To study the qualitative and quantitative analysis of organic molecules, we must first learn about and comprehend the chemical reactions that organic compounds go through, which are referred to as organic reactions.
• Substitution reactions, elimination reactions, addition reactions, oxidation-reduction reactions, and radical reactions are the five types of organic reactions.

Numerical Problems on qualitative and quantitative analysis of organic compounds 

• The qualitative and quantitative analysis of organic substances is used to solve a number of numerical difficulties. These numerical problems are necessary for calculating ionic (or atomic) mass and detecting molecular structures, and so aid in the comprehension of organic chemistry.

• The following methods or tests are used to solve numerical problems with organic quantitative analysis –

• Estimation of carbon and hydrogen by the below-given formulae – 

% C = 12/44 x Formed CO2 Mass / Mass of the substance x 100

% H = 1/18 x Formed H2 Mass / Mass of the substance x 100

• Estimation of nitrogen by

1.  Dumas method using the B  below-given formula – 

            % N = (28/22400 x (Volume of the nitrogen at NTP)) / (Mass of the compound x 100)

      (b)    Kjeldahl method

• Estimation of halogens through Carius Method using the below-given formula – 

% Halogen = Mass of the silver halide that is obtained x The atomic mass of halogen x 100 / Molar mass of the silver halide x Mass of the compound

• Estimation of sulfur by Carius method using the below-given formula – 

% S = 32/133 x Mass of BaSO4 / Mass of compound x 100

• Estimation of phosphorus using below given formula – 

% P = 62/222 x Mass of the Mg2P2O7 / Mass of compound x 100

When determining the molecular formula of a chemical. The actual number of atoms of the various elements contained in a molecule can be stated as the molecular formula. Molecular formula = (Empirical formula) x n, where n is a whole number and its value equals the value produced by dividing the molecular mass by the empirical formula mass, i.e., n = Molecular mass/ Empirical formula mass.

Conclusion

To completely comprehend the notion of qualitative and quantitative analysis of organic molecules, as well as the numerical issues based on them, extensive research is required. Prior knowledge of organic reactions and their types, organic compounds and where they are found, differences between inorganic and organic compounds, oxidation and reduction, substrate and reagent definitions, catalyst definitions and roles, how nucleophiles and electrophiles work, and the concept of bonds is required (mainly covalent bonds). Then there’s the matter of studying element detection and estimating their amount in a certain chemical complex. This is classified as an organic chemistry branch.