 #  Apply “Law of Conservation” to chemical equations What is stoichiometry?

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 Apply “Law of Conservation” to chemical equations What is stoichiometry?

Conservation of Mass The principle of conservation of mass states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products. ReactantsProduct 140 g. + 80 g. = 220 g.

LecturePLUS Timberlake3 Matter Is Conserved H 2 + Cl 2 2 HCl ++ Total atoms=Total atoms 2 H, 2 Cl2H, 2 Cl Total Mass=Total Mass 2(1.0) + 2(35.5)2(36.5) 73.0 g= 73.0 g

Balancing Chemical Equations To describe a reaction accurately, a chemical equation must show the same number of each type of atom on both sides of the equation.

5 A Balanced Chemical Equation Same numbers of each type of atom on each side of the equation Al + S Al 2 S 3 Not Balanced 2Al + 3S Al 2 S 3 Balanced 1 Aluminum atom + 1 Sulphur atom = 2 Aluminum atoms, 3 Sulphur atoms You can ONLY add whole molecules (#’s in front), not individual atoms

LecturePLUS Timberlake6 Steps in Balancing An Equation Fe 3 O 4 + H 2 Fe + H 2 O Fe: Fe 3 O 4 + H 2 3 Fe + H 2 O O:Fe 3 O 4 + H 2 3 Fe + 4 H 2 O H: Fe 3 O 4 + 4 H 2 3 Fe + 4 H 2 O

Balancing Chemical Equations Magnesium metal (Mg) reacts with oxygen gas (O 2 ), forming magnesium oxide (MgO). To write a balanced equation for this reaction, first write the equation using the formulas of the reactants and products, then count the number of atoms of each element.

Balancing Chemical Equations 1. Balance the equation for the reaction of sodium metal (Na) with oxygen gas (O 2 ), forming sodium oxide (Na 2 O). Na + O Na O 2. Balance the equation for the reaction of tin (Sn) with chlorine gas (Cl 2 ), forming tin chloride (SnCl 2 ). Sn + Cl 2 SnCl 2 2 2 2

LecturePLUS Timberlake9 Learning Check: Fill in the correct missing numbers in the equations below. A. Fe 2 O 3 + C Fe + CO 2 1) 2, 3, 2,3 2) 2, 3, 4, 3 3) 1, 1, 2, 3 B. Al + FeO Fe + Al 2 O 3 1) 2, 3, 3, 1 2) 2, 1, 1, 1 3) 3, 3, 3, 1 C. Al + H 2 SO 4 Al 2 (SO 4 ) 3 + H 2 1) 3, 2, 1, 2 2) 2, 3, 1, 3 3) 2, 3, 2, 3

LecturePLUS Timberlake10 Solution A. (2) 2 Fe 2 O 3 + 3 C 4 Fe + 3 CO 2 B. (1) 2 Al + 3 FeO 3 Fe + Al 2 O 3 C. (2) 2 Al + 3 H 2 SO 4 Al 2 (SO 4 ) 3 + 3 H 2

Extension Activity Balancing equations battleships Finish “What is Matter?” packet INDEPENDENTLY & turn in.

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