An organic compound ( \(3.0 \mathrm{~g}\) ) gave on complete combustion, \(3.476 \mathrm{~g}\) of \(\mathrm{CO}_{2}\) and \(1.422 \mathrm{~g}\) of water. The molecular weight of the compound is 228 . Give molecular formula of the compound.

Grasping the concept of an empirical formula is essential for students tackling molecular composition. The empirical formula is the simplest integer ratio of the elements within a compound. To calculate it, you must follow a series of steps starting with the quantification of individual elements involved.

Here's a practical approach to determine the empirical formula from given data:

• Firstly, determine the amount of each element present in the sample. This is usually measured in grams.
• Convert these masses into moles using the molar mass of each respective element.
• Divide the moles of each element by the smallest number of moles calculated for any of the elements.
• If any ratios are not whole numbers, multiply all the ratios by the same factor to achieve a set of integers.

For example, when a compound yields certain quantities of CO₂ and H₂O upon combustion, you can use this information to deduce the ratio of carbon and hydrogen in the original compound. If the ratios aren't whole numbers, as seen in the problem, the values are scaled by a common multiple, which, in this case, is 2, to ensure whole number subscripts in the chemical formula.

Analytical chemistry provides a powerful tool known as combustion analysis to determine the composition of unknown substances, particularly organic compounds. This technique involves burning a known mass of a compound in an excess of oxygen to produce CO₂ for carbon analysis and H₂O for hydrogen analysis.

Key Steps in Combustion Analysis

Following the combustion, the products are collected, and their masses are measured. These masses are then used to calculate the number of moles of carbon and hydrogen, which correlates directly to the moles of these elements in the original compound:

• The mass of CO₂ produced provides the total amount of carbon.
• Similarly, the mass of H₂O indicates the total amount of hydrogen.

By subtracting the combined masses of carbon and hydrogen from the initial mass of the organic compound, the mass of oxygen (or any other non-volatile elements) can be determined. This comprehensive understanding of combustion analysis is instrumental for students when they are presented with such experimental data.

A deep understanding of stoichiometry is crucial for solving various chemical problems, including the determination of molecular formulas. Stoichiometry is the area of chemistry that concerns the quantitative relationships of the substances as they participate in chemical reactions.

It involves using balanced chemical equations to calculate the relative amounts of reactants and products:

• Molar Ratios: These ratios are derived from the coefficients of a balanced chemical equation and are used to convert between moles of one substance to moles of another.
• Molar Mass: The mass of one mole of a substance, usually in grams per mole, which is vital for converting between mass and moles of a substance.
• Limiting Reagents: The reactant that is completely consumed in a reaction. This determines the maximum amount of product that can be formed.

Applying stoichiometry to the given exercise, once the empirical formula has been established, the molecular formula can then be found by comparing the molecular weight of the compound with the mass of the empirical formula unit. The final step is to apply the appropriate multiplication factor, as indicated by the example where the factor was nearly 4. This step is crucial because the empirical formula needs to be multiplied by this factor to result in the actual molecular formula of the compound being analyzed.