Empirical formula - wikipedia Empirical formula This article is about analytical chemistry. For observation rather than theory, see Empirical relationship. In chemistry, the empirical formula of a chemical compound is the simplest positive integer ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulfur monoxide, or SO, would simply be SO, as is the empirical formula of disulfur dioxide, S O. This means that sulfur monoxide and disulfur dioxide, both compounds of sulfur and oxygen, will have the same empirical formula. However, their chemical formulas, which express the number of atoms in each molecule of a chemical compound, may not be the same. An empirical formula makes no mention of the arrangement or number of atoms. It is standard for many ionic compounds, like calcium chloride ( CaCl ), and for macromolecules, such as silicon dioxide ( SiO ). The molecular formula, on the other hand, shows the number of each type of atom in a molecule. The structural formula shows the arrangement of the molecule. It is also possible for different types of compounds to have equal empirical formulas. Samples are analyzed in specific elemental analysis tests to determine what percent of a particular element the sample is composed of. Examples Glucose ( C H O ), ribose ( C H O ), acetic acid ( C H O ), and formaldehyde ( CH O ) all have different molecular formulas but the same empirical formula : CH O. This is the actual molecular formula for formaldehyde, but acetic acid has double the number of atoms, ribose has five times the number of atoms, and glucose has six times the number of atoms. The chemical compound n - hexane has the structural formula CH CH CH CH CH CH, which shows that it has 6 carbon atoms arranged in a chain, and 14 hydrogen atoms. Hexane 's molecular formula is C H, and its empirical formula is C H, showing a C : H ratio of 3 : 7. Calculation Suppose you are given a compound such as methyl acetate, a solvent commonly used in paints, inks, and adhesives. When methyl acetate was analyzed in an elemental analysis test, the compound was found to contain 48.64 % carbon ( C ), 8.16 % hydrogen ( H ), and 43.20 % oxygen ( O ). For the purposes of determining empirical formulas, we assume that we have 100 g of the compound. If this is the case, the percentages will be equal to the mass of each element in grams. Step 1 Change each percentage to an expression of the mass of each element in grams. That is, 48.64 % C becomes 48.64 g C, 8.16 % H becomes 8.16 g H, and 43.20 % O becomes 43.20 g O. Step 2 Convert the amount of each element in grams to its amount in moles. ( 48.64 g C 1 ) ( 1 mol 12.01 g C ) = 4.049 mol ( displaystyle left ( ( \frac ( 48.64 ( mbox ( g C ) ) ) ( 1 ) ) \right ) left ( ( \frac ( 1 ( mbox ( mol ) ) ) ( 12.01 ( mbox ( g C ) ) ) ) \right ) = 4.049 ( \text ( mol ) ) ) ( 8.16 g H 1 ) ( 1 mol 1.008 g H ) = 8.095 mol ( displaystyle left ( ( \frac ( 8.16 ( mbox ( g H ) ) ) ( 1 ) ) \right ) left ( ( \frac ( 1 ( mbox ( mol ) ) ) ( 1.008 ( mbox ( g H ) ) ) ) \right ) = 8.095 ( \text ( mol ) ) ) ( 43.20 g O 1 ) ( 1 mol 16.00 g O ) = 2.7 mol ( displaystyle left ( ( \frac ( 43.20 ( mbox ( g O ) ) ) ( 1 ) ) \right ) left ( ( \frac ( 1 ( mbox ( mol ) ) ) ( 16.00 ( mbox ( g O ) ) ) ) \right ) = 2.7 ( \text ( mol ) ) ) Step 3 Divide each of the found values by the smallest of these values ( 2.7 ) 4.049 mol 2.7 mol = 1.5 ( displaystyle ( \frac ( 4.049 ( mbox ( mol ) ) ) ( 2.7 ( mbox ( mol ) ) ) ) = 1.5 ) 8.095 mol 2.7 mol = 3 ( displaystyle ( \frac ( 8.095 ( mbox ( mol ) ) ) ( 2.7 ( mbox ( mol ) ) ) ) = 3 ) 2.7 mol 2.7 mol = 1 ( displaystyle ( \frac ( 2.7 ( mbox ( mol ) ) ) ( 2.7 ( mbox ( mol ) ) ) ) = 1 ) Step 4 If necessary, multiply these numbers by integers in order to get whole numbers ; if an operation is done to one of the numbers, it must be done to all of them. 1.5 × 2 = 3 ( displaystyle 1.5 \times 2 = 3 ) 3 × 2 = 6 ( displaystyle 3 \times 2 = 6 ) 1 × 2 = 2 ( displaystyle 1 \times 2 = 2 ) Thus, the empirical formula of methyl acetate is C H O. This formula also happens to be methyl acetate 's molecular formula. References Jump up ^ IUPAC, Compendium of Chemical Terminology, 2nd ed. ( the `` Gold Book '' ) ( 1997 ). Online corrected version : ( 2006 -- ) `` Empirical formula ''. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Empirical_formula&oldid=818624340 '' Categories : Chemical formulas Analytical chemistry Talk About Wikipedia Bân - lâm - gú Български Bosanski Brezhoneg Català Cymraeg Dansk Deutsch Eesti Español Esperanto فارسی Galego 한국어 हिन्दी Hrvatski Bahasa Indonesia Italiano עברית Kreyòl ayisyen Magyar മലയാളം Bahasa Melayu Nederlands 日本 語 Norsk Plattdüütsch Polski Português Română Русский Simple English Slovenčina کوردی Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska தமிழ் Українська اردو 中文 Edit links This page was last edited on 4 January 2018, at 17 : 04. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. 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Question: what is the empirical formula of a compound
Answer: the simplest positive integer ratio of atoms present in a compound