L18a-c_Unit_7a-3_ALL[1]

023 x 1023 par9cles consider the water molecule h2o 1

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Unformatted text preview: Every reac9on has a fixed mole ra9o that can be used for STOICHIOMETRY calcula9ons Prac<ce Problem 1 Magnesium reacts with oxygen to produce magnesium oxide. If you have 3.2 moles of Mg, how many moles of O2 are required to completely react the Mg? Step 1: Step 2: 2Mg(s) + O2(g) ! 2MgO(s) Moles O2 = Moles Mg x ra9o (O2/Mg) = 3.2 x (1/2) = 1.6 moles of O2 Prac<ce Problem 2 C3H8 is an organic compound that reacts with oxygen to produce carbon dioxide and water. If 44.6 moles of C3H8 react, how many moles of carbon dioxide are formed? Step 1: C3H8 + 5O2 ! 3CO2 + 4 H2O Step 2: Moles CO2 = Moles C3H8 x ra9o (CO2/C3H8) = 44.6 x (3/1) = 133.8 moles of O2 Prac<ce Problem 3 Diphosphorous pentoxide is oien used as a drying reagent because it effec<vely removes water by reac<ng with it in solu<on. If I react 1.87 moles of diphosphorous pentoxide with water to produce trihydrogen phosphate (aka phosphoric acid), how many moles of water are consumed in this reac<on? Step 1: P2O5 (s) + 3H2O (l) ! 2H3PO4 (aq) Step 2: Moles H2O = Moles P2O5 x ra9o (H2O/P2O5 ) = 1.87 x (3/1) = 5.61 moles of H2O But what is the MOLE? The Mole is a unit that represents a very very big number A number big enough to represent so many atoms that we can see them MACROSCOPICALLY 1 mole = 6.023 x 1023 par9cles This is called Avogadro’s number This is the SAME for all elements and compounds The MOLE also represents a specified mass of a substance 1 mole = specified # grams (MOLAR MASS ) Each element on the...
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This note was uploaded on 02/01/2014 for the course CHEM 102 taught by Professor Peterpastos during the Fall '08 term at CUNY Hunter.

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