Chemists mole concept used

The actual number of atoms in one mole of an element has been determined by several elegant experimental procedures to be 6.02 X 10 This quantity is known as Avogadro s number, in honor of one of the pioneers of the atomic theory. One can then see that one mole of carbon atoms (12.01 grams) will contain exactly the same number of atoms as one mole (55.85 grams) of iron. Using the mole concept, the chemist can now go into the laboratory and weigh out equal quantities of atoms of the various elements. 

Molarity is the concentration unit most often used by chemists, because it utilizes moles. The mole concept is central to chemistry, and molarity lets chemists easily work solutions into reaction stoichiometry. (U you re cussing me out right now because you have no idea what burrowing, insect-eating mammals have to do with chemistry, let alone what stoichiometry is, just flip to Chapter 10 for the scoop. Your mother would probably recommend washing your mouth out with soap first.)... 

The mole is often referred to as a chemist s unit of quantity. Counting atoms is a difficult process and beyond the scope of most calculators, but measuring the mass of a sample is easy when we can relate the number of atoms in a sample to its mass. This is the unique purpose of the mole. A mole of any substance is its molecular formula weight expressed in grams. Avogadro s number s a universal constant that states the number of molecules in a mole Nq = 6.023 x 10 molecules/mole. One mole (abbreviated mol) of any element (chemical compound) has the same number of chemical particles as one mole of another element (chemical compound). In other words, 1 mole of any compound contains 6.02 x 10 molecules. Review the following problem using the mole concept. 

A biologist can use the periodic table in same way as a chemist. It can be used to find elements with similar chemical properties, predict chemical formulas, predict charges on simple ions, predict electron structures of atoms and ions, find simple ions of similar ionic radius, predict physical and chemical properties, and relative atomic masses can be used in calculations involving the mole concept. 

Some chemists feel that the mole is an unnecessary SI unit as they make measurements in mass/mass or mass/ volume units, using ratio methods. The definition and the importance of the mole has been discussed elsewhere [8], and the distinction has been made between its importance as a concept, the importance of the related atomic mass values, and the lesser role of the mole as a unit for actually reporting results. A distinctive feature of the mole is the need to define the entity . This is an extra dimension compared with other SI units. For example, it is not necessary to ask, is this a mass when measuring the mass of an object, in the way that it is critical to ask, is this lead before attempting to measure the amount of lead. A mole measurement thus requires two issues to be addressed, namely identity and amount. It follows therefore that traceability claims must show unbroken chains covering both of these issues. It is because of the existence of a vast number of chemical species that it is necessary to clearly specify and separate the specified chemical entities from all other possible chemical entities prior to measurement. This leads to complex chemical measurement processes, with considerable attention to validation of the measurement method being required. 

In the previous section, you learned how to calculate the percentage composition of a compound from its chemical formula. Now you will do the reverse. You will use the percentage composition of a compound, along with the concept of the mole, to calculate the empirical formula of the compound. Since the percentage composition can often be determined by experiment, chemists use this calculation when they want to identify a compound. 

Chemists use a number that is similar in concept to the dozen. However, 12 is too small a number when referring to atoms. We need a much larger number because atoms are so small. Consequently, the chemist s dozen is called the mole (mol) and corresponds to 6.022 X 10. This number is called Avogadro s number, named after Amadeo Avogadro (1775-1856), and is a convenient number to use when speaking of atoms. A mole of atoms contains 6.022 X 10 atoms and makes up objects of reasonable sizes. For example, 22 pure copper pennies (pre-1983) contain approximately one mole of copper atoms, and a few large helium balloons contain approximately one mole of helium atoms. There is nothing mysterious about a mole it is just a certain number of objects, 6.022 X 10, just like a dozen is a certain number of objects, 12. 

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