Chemical formulas of a compound

The chemical formula of a compound represents its composition in terms of chemical symbols. Subscripts show the numbers of atoms of each element present in the smallest unit that is representative of the compound. For molecular compounds, it is common to give the molecular formula, a chemical formula that shows how many atoms of each type of element are present in a single molecule of the compound. For instance, the molecular formula for water is H20 each molecule contains one O atom and two H atoms. The molecular formula for estrone, a female sex hormone, is Clgl-I2202, showing that a single molecule of estrone consists of 18 C atoms, 22 FI atoms, and 2 O atoms. A molecule of a male sex hormone, testosterone, differs by only a few atoms its molecular formula is (lyH2802. Think of the consequences of that tiny difference ... 

If the chemical formula of a compound is already known, its mass percentage composition can be obtained from the formula. 

The chemical formula of a compound contains essential information about its composition. The formula identifies which elements are present, and it states the number of atoms of each kind present in one unit of the compound. We need the chemical formula of a substance to calculate its molar mass. In fact, almost all chemical calculations require the correct chemical formula. How are chemical formulas determined in the first place ... 

To assign a chemical formula of a compound from its name, you first must recognize whether the compound is ionic or molecular. For ionic compounds, you must also know the charges on the ions. 

So far we have started with the chemical formula of a compound and decided on its systematic name. The reverse process is also important. For example, given the name calcium hydroxide, we can write the formula as Ca(OH)2 since we know that calcium forms only Ca2+ ions and that, since hydroxide is OH-, two of these anions will be required to give a neutral compound. Similarly, the name iron(II) oxide implies the formula FeO, since the Roman numeral II indicates the presence of Fe2+ and since the oxide ion is O2-. 

REMEMBER, you cannot change the chemical formula of a compound in order to help to balance the equation. 

Percentage Composition, and using the Law of Constant Composition to find the Empirical and Chemical Formula of a Compound... 

As you know, the chemical formula of a compound tells you the elements that comprise it. For example, the formula for geraniol (the main compound that gives a rose its scent) is CjoHigO. The formula shows that geraniol is comprised of carbon, hydrogen, and oxygen. Because all these elements are nonmetals, geraniol is probably covalent and comprised of molecules. 

The chemical formula of a compound can be determined if the molar mass and the empirical formula are known. 

Given the name or chemical formula of a compound, identify whether it would be better to use the term molecule or the term formula unit to describe the group that contains the number of atoms or ions of each element equal to the subscript for the element in its chemical formula. 

Avogadro s number, molar mass, and the chemical formula of a compound are three useful conversion factors. What unit conversions can be accomplished using these conversion factors ... 

As far as polymers go, the problem is to decide what monomer units make up the chain. What a stupid question , a chemist would say. If the chemical formula of a compound is An, and it is made up of lots of A molecules, then surely A is the monomer unit. However, why can you not connect the A molecules in twos, and then link all the N/2 dimers A2 together Or, alternatively, why not link together groups of three monomer units, etc, etc So ... 

Analyze Given tire chemical formula of a compound, C12H22O11, we are asked to calculate its percentage composition, meaning the percent by mass of its component elements (C, H, and O). 

We just learned how to go from the chemical formula of a compound to its mass percent composition. Can we also go the other way ... 

The chemical formula of a compound represents the lowest whole-number ratio of the atoms or ions. 

The chemical formula of a compound provides the relative number of atoms (or moles) of each element in a compound and can therefore be used to determine numerical relationships between moles of the compound and moles of its constituent elements. This relationship can be extended to mass by using the molar masses of the compound and its constituent elements. 

We have seen that the subscripts in the chemical formula of a compound indicate the number of atoms of each type of element in the compound. For example, aspirin, C9Hg04, is a drug used to reduce pain and inflammation in the body. Using the subscripts in the chemical formula of aspirin shows that there are 9 carbon atoms, 8 hydrogen atoms, and 4 oxygen atoms in each molecule of aspirin. The subscripts also tell us the number of moles of each element in 1 mole of aspirin 9 moles of C atoms, 8 moles of H atoms, and 4 moles of O atoms. 

For Berthelot, the chemical formula of a compound does not serve as a description of a hypothetical molecular reality it is the result of an action, and offers a precis of the synthetic process, what he termed a generative equation . Thus, Berthelot concluded that benzene was an isomer of acetylene because, when heated to 600°C, acetylene produced a liquid containing traces of benzene, which he could isolate by fractional distillation. Nevertheless, this strategy had little future. By contrast, the chemists who based their research on August von Kekule s hypothesis concerning the structure of the benzene molecule were able to produce a cornucopia... 

Once we know the chemical formula of a compound, we can determine its formula mass. Formula mass is the mass of a. formula unit in atomic mass units. It is always appropriate to use the term formula mass, but, for a molecular compound, the formula unit is an actual molecule, so we can speak of molecular mass. Molecular mass is the mass of a molecule in atomic mass units. 

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