CHEM 1411 Lab Report Chemical Formulas Te.docx

CHEM 1411 Lab Report Chemical Formulas Te.docx - Christian...

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Christian Smith Dr. Mo. Chehbouni Saturday, October 8, 2016 Chemical Formulas Objective: To determine the empirical formulas of two chemical compounds then to determine the combining (mole) ratios of the elements. Introduction: When talking about and making calculations with chemicals we simplify the process by using symbols and formulas. Each element is represented by a symbol which is generally the first 2 letters of the element’s name; of course we must note that in a lot of cases the symbol is derived from the name of the element in a different language, such as Greek. When two or more atoms are bonded together we get what are called molecules. Some atoms appear naturally as molecular bonds of two or more of the same atom (such as O 2 ), molecules with more than one type of atom are called compounds. We represent the reaction of two or more compounds and/or molecules by chemical formulas. Formulas include the symbols of the elements involved as well as numbers indicating the relative number of each element. Chemical formulas can be represented by either their molecular or empirical formulas where molecular are the actual formula and empirical are the lowest whole number ratio of the formula. Since atoms and molecules are so small it would be cumbersome to represent their mass with units of grams. For this reason we instead use the atomic mass unit (abbreviated as amu) which is the same as 1.66054 x 10 -24 grams. The atomic weight of of an element is defined as the average weight of the isotopes (atoms with differing numbers of neutrons) in the element, this is the weight of the element represented in the periodic table. Adding together all of the atomic weights in a molecule or compound gives what is called the formula weight. Knowing the atomic weights of different elements is nice, however it doesn’t do us much good unless we’re able to determine the amount of the element present, enter the mole. The mole is merely a unit like the dozen that represents a number, Avogadro’s number: 6.02 x 10 23 . So, for example, 1 mole of Oxygen would be 6.02 x 10 23 molecules of O 2 . This unit is important because it relates the number of atoms/molecules to the mass via the atomic weight by the relation whereby the atomic weight of 1 mole of a substance is numerically equal to its weight in grams.
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