Chapter 12 Notes

Information given by chemical equations 2 C 6 H 6 (l) + 15 O 2 (g)  12 CO 2 (g) + 6 H 2 O (g)  In this equation there are 2 molecules of benzene reacting with 15 molecules of oxygen to produce 12 molecules of carbon dioxide and 6 molecules of water  In this equation there are 2 molecules of benzene reacting with 15 molecules of oxygen to produce 12 molecules of carbon dioxide and 6 molecules of water.  This equation could also be read as 2 moles of benzene reacts with 15 moles of oxygen to produce 12 moles of carbon dioxide and 6 moles of water.

Information given by chemical equations 2 C 6 H 6 (l) + 15 O 2 (g)  12 CO 2 (g) + 6 H 2 O (g) The MOLE RATIO for benzene and oxygen is 2 : 15. It can be written as: 2 moles C 6 H 6 or as 15 moles of O 2 15 moles O 2 2 moles of C 6 H 6 The MOLE RATIO for oxygen and carbon dioxide is 15 : 12. It can be written as: 12 moles CO 2 or as 15 moles of O 2 15 moles O 2 12 moles of CO 2 NOTE: The MOLE RATIO is used for converting moles of one substance into moles of another substance. Without the balanced equation there is no other relationship between two different compounds.

Using the mole ratio to relate the moles of one compound to the moles of another compound is the part of chemistry called STOICHIOMETRY !!!!! 2 H 2 (g) + O 2 (g) 2 H 2 O (g) 2 H 2 (g) + O 2 (g)  2 H 2 O (g) Q. How many mole of hydrogen are necessary to react with 2 moles of oxygen in order to produce exactly 4 moles of water? A. 2 mol O 2 (2 moles H 2 / 1 mole O 2 ) = 4 mole H 2

STOICHIOMETRY The Stoichiometry Flow Chart Use Molar mass (A) Use mole ratio from equation Use Molar mass (B)

STOICHIOMETRY 2 H 2 (g) + O 2 (g) 2 H 2 O (g) 2 H 2 (g) + O 2 (g)  2 H 2 O (g) Q1. How many moles of hydrogen are necessary to react with 15.0 g of oxygen? A. 15.0g O 2 ( 1 mole O 2 ) ( 2 mole H 2 ) = moles H g 1 mole O 2 Q2. How many grams of hydrogen are necessary to react with 15.0 g of oxygen? A. 15.0g O 2 ( 1 mole O 2 ) ( 2 mole H 2 ) ( g H 2 ) = 1.89 g H g 1 mole O 2 1 mole H 2

STOICHIOMETRY 2 H 2 (g) + O 2 (g)  2 H 2 O (g) Q3. How many grams of water are produced from 15.0 g of oxygen? A. 15.0g O 2 ( 1 mole O 2 ) ( 2 mole H 2 O ) ( 18.0 g H 2 O ) =16.9 g H 2 O 32.0 g 1 mole O 2 1 mole H 2 O Q4. How much hydrogen and oxygen is needed to produce 25.0 grams of water? A. 25.0g H 2 O ( 1 mole H 2 O ) ( 2 mole H 2 ) ( g H 2 ) = 2.80 g H g 2 mole H 2 O 1 mole H 2 A. 25.0g H 2 O ( 1 mole H 2 O ) ( 1 mole O 2 ) ( 32.0 g O 2 ) = 22.2 g O g 2 mole H 2 O 1 mole O 2 Notice that the Law of Conservation of Mass still applies.

Q5. How many grams of solid are formed when 10.0 g of lead reacts with excess phosphoric acid? 1.Write the chemical equation: Pb + H 3 PO 4  ? Pb + H 3 PO 4  Pb 3 (PO 4 ) 2 + H 2 2. Balance the equation: 3 Pb+2 H 3 PO 4  Pb 3 (PO 4 ) H 2 3. Make a list under the appropriate substance 3 Pb+2 H 3 PO 4  Pb 3 (PO 4 ) 2 (s) + 3 H 2 (g) 10.0gm=? Start with what is given: 13.1 g Pb 3 (PO 4 ) gPb ( 1 mole Pb )( 1 mole Pb 3 (PO 4 ) 2 )( 811 g Pb 3 (PO 4 ) 2 ) = 13.1 g Pb 3 (PO 4 ) g Pb 3 mole Pb 1 mole Pb 3 (PO 4 ) 2

Q6. A. Hydrogen Gas and Oxygen Gas produces Water. B. How many liter of hydrogen are required to react completely with 5 liters of oxygen gas? C. If 20 grams of hydrogen react with an excess of oxygen how many grams of water will form? D. If 7 moles of water forms how many moles of hydrogen must react?

PRACTICE PROBLEM 1. How many grams of gas can be produced from moles of HgO decomposing? 2. How many moles of fluorine are required to produce 12.0 grams of KrF 6 ? Given the equation: Kr + 3 F 2  KrF 6 4. How many grams of CO 2 can be produced by the reaction of 75.0 grams of C 2 H 2 with excess oxygen? 5. How many grams of silver is produced when g of copper is reacted with excess silver nitrate solution? 14.20g mol 254 g g