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Unformatted text preview: Molarity This is a short tutorial that I prepared to help you understand Molarity. Please view it as a presentation rather than just looking at the slides in the editor mode. It will benefit you more, as you will not immediately see the correct answer should you wish to test your knowledge. Good Luck, Chris Molarity Molarity (M) is simply a measure of concentration, similar to percent or parts per thousand . It tells us how many moles (mol) of a substance per 1 liter of water. A mole is a word with a numerical definition; it is equal to 6.023 x 10 23 of something. Normally, we use it when we discuss the number of atoms or molecules in a given weight of that sample. The molecular weight (when referring to molecules) or atomic weight (when discussing individual atoms) refers to the weight of 1 mole of that substance. For example, if we look at carbon (C) on the periodic table, its atomic weight is 12.001, which tells us that there is 1 mole of carbon (or 6.023 x 10 23 ) atoms of carbon in ~12 grams of carbon. If we were discussing a molecule like C0 2 , then we would add the individual atomic weights to calculate the molecular weight. To help think about it, consider the term, Dozen, which also has a numerical definition of 12. You can have a dozen of anything, while you can have a mole of anything (however, since one mole is such a large number, we dont commonly use it in every day conversation). Let assume that = 1 mole of Oxygen The atomic weight of Oxygen = ~16 g/mol, so the molecular weight of O 2 = (16 g/mol x 2) = 32 g/mol. That means there are 6.023 molecules of O 2 in 1 mole of O 2. O 2 1 liter (L) of water or 1000 milliliters (ml) This is a very simple situation where we have 1 mole of oxygen dissolved in 1 liter of water, which means this is a 1 Molar solution. O 2 1 Molar O 2 Molarity Molarity (M) is simply a measure of concentration, similar to percent or parts per thousand . It tells us how many moles (mol) of a substance per 1 liter of water. A mole is a word with a numerical definition; it is equal to 6.023 x 10 23 of something. Normally, we use it when we discuss the number of atoms or molecules in a given weight of that sample. The molecular weight (when referring to molecules) or atomic weight (when discussing individual atoms) refers to the weight of 1 mole of that substance. For example, if we look at carbon (C) on the periodic table, its atomic weight is 12.001, which tells us that there is 1 mole of carbon (or 6.023 x 10 23 ) atoms of carbon in ~12 grams of carbon. If we were discussing a molecule like C0 2 , then we would add the individual atomic weights to calculate the molecular weight. To help think about it, consider the term, Dozen, which also has a numerical definition of 12. You can have a dozen of anything, while you can have a mole of anything (however, since one mole is such a large number, we dont commonly use it in every day conversation)....
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This note was uploaded on 08/31/2010 for the course BIO 49810 taught by Professor Satasivan during the Spring '10 term at University of Texas at Austin.
 Spring '10
 Satasivan

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