empirical formula

Examples of empirical formula in the following topics:

• Molecular Formulas

  • In this case, the empirical formula of glucose is CH2O.
  • To convert between empirical and molecular formulas, the empirical formula can be multiplied by a whole number to reach the molecular formula.
  • In this case, the empirical formula would be multiplied by 6 to get to the molecular formula.
  • The compound dichlorine hexoxide has an empirical formula ClO3 and the molecular formula Cl2O6
  • The compound hydrogen peroxide has the empirical formula HO and the molecular formula H2O2

• Empirical Formulas

  • The molecular formula for a compound is equal to, or a whole-number multiple of, its empirical formula.
  • The empirical formula is the lowest possible whole-number ratio of the elements.
  • The empirical formula of decane is C5H11.
  • Therefore, if the empirical formula of decane is C5H11, the molecular formula of decane is twice that, or C10H22.
  • This video shows how to go from the molecular formula of a compound to its corresponding empirical formula.

• Polyatomic Molecules

  • A molecule's chemical formula and structure are the two important factors that determine its properties, particularly reactivity.
  • A compound's empirical formula is the simplest integer ratio of its constitutional chemical elements.
  • For example, carbohydrates have the same ratio (carbon: hydrogen: oxygen = 1:2:1) and thus the same empirical formula, but have different total numbers of atoms in the molecule.
  • The molecular formula characterizes different molecules by reflecting their exact number of compositional atoms.
  • The empirical formula is often the same as the molecular formula, but not always; for example, the molecule acetylene has molecular formula C2H2, but the simplest integer ratio of elements is CH.

• Molecules

  • Often, a compound's composition can also be denoted by an empirical formula, which is the simplest integer ratio of its constituent chemical elements.
  • However, this empirical formula does not always describe the specific molecule in question, since it provides only the ratio of its elements.
  • The full elemental composition of a molecule can be precisely represented by its molecular formula, which indicates the exact number of atoms that are in the molecule.
  • The chemical formula for propanol (C3H7OH) describes several different molecules, which vary by the position of the alcohol (OH).

• Formulas of Ionic Compounds

  • Ionic solids are typically represented by their empirical formulas.
  • The complete formula for an ionic compound can be determined by satisfying two conditions:
  • Its ionic formula is written as CaCl2, the neutral combination of these ions.
  • For example, the hydroxide ion has the formula OH-1.
  • Generate the empirical formula of an ionic compound given its molecular constituents.

• Percent Composition of Compounds

  • The atomic composition of chemical compounds can be described using a variety of notations including molecular, empirical, and structural formulas.
  • For example, butane has a molecular formula of C4H10.
  • Mass percents can be determined experimentally via elemental analysis, and these values can be used to calculate the empirical formula of unknown compounds.
  • However, this information is insufficient to determine the molecular formula without additional information on the compound's molecular weight.
  • Translate between a molecular formula of a compound and its percent composition by mass

• Combustion Analysis

  • Combustion analysis is commonly used to analyze samples of unknown chemical formula.
  • The data and the ratios can then be used to calculate the empirical formula of the unknown sample.

• Formulas of Ionic Compounds

  • Ionic formulas must satisfy the noble gas configurations for the constituent ions and the product compound must be electrically neutral.
  • In addition, though any ratio of 2 bromine atoms to 1 magnesium atom will satisfy the two requirements above, the formula for ionic compounds is typically presented as the empirical formula, or the simplest whole-number ratio of atoms with positive integers.
  • Note that the cation always precedes the anion both in written form and in formulas.
  • A lesson on writing formulas for binary ionic compounds as well as ionic compounds containing polyatomic ions.
  • Apply knowledge of ionic bonding to predict the formula of ionic compounds

• The Bohr Model

  • Although it challenged the knowledge of classical physics, the model's success lay in explaining the Rydberg formula for the spectral emission lines of atomic hydrogen.
  • While the Rydberg formula had been known experimentally, it did not gain a theoretical underpinning until the Bohr model was introduced.
  • Not only did the Bohr model explain the reason for the structure of the Rydberg formula, it also provided a justification for its empirical results in terms of fundamental physical constants.
  • The Bohr theory solved this problem and correctly explained the experimentally obtained Rydberg formula for emission lines.
  • Like Einstein's theory of the photoelectric effect, Bohr's formula assumes that during a quantum jump, a discrete amount of energy is radiated.

• A Structure Formula Relationship

  • Recall that the molecular formula of a hydrocarbon (CnHm) provides information about the number of rings and/or double bonds that must be present in its structural formula.
  • In the formula shown below a triple bond is counted as two double bonds.
  • This molecular formula analysis may be extended beyond hydrocarbons by a few simple corrections.
  • All halogens present in the molecular formula must be replaced by hydrogen.
  • Each nitrogen in the formula must be replaced by a CH moiety.