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From Wikipedia

Empirical formula

In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms of each element present in a compound. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The empirical formula is used as standard for most ionic compounds, such as CaCl2, and for macromolecules, such as SiO2. The term empirical refers to the process of elemental analysis, a technique of analytical chemistry used to determine the relative amounts of each element in a chemical compound.

In contrast, the molecular formula identifies the number of each type of atom in a molecule, and the structural formula also shows the structure of the molecule.

For example, the chemical compound n-hexane has the structural formula CH|3|CH|2|CH|2|CH|2|CH|2|CH|3, which shows that it has 6 carbon atoms arranged in a straight chain, and 14 hydrogen atoms. Hexane's molecular formula is C|6|H|14, and its empirical formula is C|3|H|7, showing a C:H ratio of 3:7. Different compounds can have the same empirical formula. For example, formaldehyde, acetic acid and glucose have the same empirical formula, CH|2|O. This is the actual chemical formula for formaldehyde, but acetic acid has double the number of atoms and glucose has six times the number of atoms.

Examples of common substances

Use in physics

In physics, an empirical formula is a mathematical equation that predicts observed results, but is derived from experiment or conjecture and not directly from first principles.

An example was the Rydberg formula to predict the wavelengths of hydrogen spectral lines. Proposed in 1888, it perfectly predicted the wavelengths of the Lyman series, but lacked a theoretical basis until Niels Bohr produced his Bohr model of the atom in 1913.



From Yahoo Answers

Question:Enter the empirical formula for acetone, given that its molecular formula is C3H6O. Enter formula in form of Cx Hy Oz. Omit coefficient if equal to 1

Answers:acetone is... .........O .........|| CH3 - C - CH3 so it's molecular formula is definitely C3H6O... the empirical formula is the lowest whole number ratios of atoms. 3:6:1 is the lowest whole number ratio.... so enter... C3 H6 O.... that should work.

Question:a. What is the empirical formula of C2H4? b. What is the empirical formula of C4H10O2? Please help! Thanks xxx

Answers:its the simplest ratio CH C2H5O

Question:An alcohol is 52.13% C, 13.15% H, and 34.72% O by mass. What is the empirical formula of the alcohol?

Answers:in 100 g of our alcohol we have 52.13g of C or 52.13 / 12 moles of C = 4.344 moles 13.15 g of H or 13.15 moles of H and 34.72g of O 2.17 moles of O = 2.17 molar ratio of C : H : O = 4.344 : 13.15 : 2.17 or after dividing by the smallest 2:6:1 empirical formula is C2H6O .. possibly ethanol but we need am molar mass to be sure ..

Question:I know what an empirical formula is so no need to answer that question. My question is: What are the uses of empirical formula? I've been solving for empirical formulas for about 2 years now and I still don't know what are their applications to life. Please answer this cause I need it for my lab report.

Answers:Emprical means known by experiment. So emperical formula means a formula known by experiment. The need of emperical formula is actually needed in the lab when you go for chemical reactions. You must add chemical in amount as defined by the emprical formula. For eg. Sulphate (SO4) combine in the ratio of 1: 4 That means 1 suphate combines with 4 oxygen atoms. in a reaction.

From Youtube

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