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Chemical Reactions Notes
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Chemical Reaction Definition: When substances combine to form a new substances.
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Chemical Equations… Uses symbols to show reactants + products of a chemical reaction. REACTANTS: materials that you start with (left side) PRODUCTS: materials that you end with (right side) EXAMPLE: 2 H 2 + O 2 2 H 2 O reactants products Uses symbols to show reactants + products of a chemical reaction. REACTANTS: materials that you start with (left side) PRODUCTS: materials that you end with (right side) EXAMPLE: 2 H 2 + O 2 2 H 2 O reactants products
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1. Practice Questions: 4 Al + 3 O 2 2 Al 2 O 3 ProductsReactants
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2. Practice Questions: CO + 2H 2 CH 3 OH ProductsReactants
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3. Practice Questions: AgNO 3 + NaCl AgCl + NaNO 3 ProductsReactants
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4. Practice Questions: 3Fe + 2O 2 Fe 3 O 4 3Fe + 2O 2 Fe 3 O 4 Products Reactants
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C. Law of Conservation of Mass mass of products = mass of reactants What goes in…must come out! mass of products = mass of reactants What goes in…must come out!
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Example: 2 H 2 + O 2 2 H 2 O reactants products Elements: H + O
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Practice Questions 1. What elements would be the reactants? products: Sn + 2H 2 O 1. What elements would be the reactants? products: Sn + 2H 2 O Sn, H, O
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Practice Questions 2. What elements would be the reactants? products: 2 Al 2 O 3 2. What elements would be the reactants? products: 2 Al 2 O 3 Al, O
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Practice Questions 3. What elements would be the products? reactants: 2 Fe + 2 H 2 SO 4 3. What elements would be the products? reactants: 2 Fe + 2 H 2 SO 4 Fe, H, S, O
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Counting the molecules and compounds: Coefficient: the number in front of the chemical formula - it tells how many molecules of a substance. 2 Fe
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Example: 2 H 2 O atoms of “H” per molecule atoms of “O” per molecule atoms of “H” total atoms of “O” total 2 H 2 O atoms of “H” per molecule atoms of “O” per molecule atoms of “H” total atoms of “O” total 2 1 4 2 The coefficient times subscript = the number of atoms total!!!
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This equation is balanced because the number of H’s and O’s on product and reactant sides are equal. 2 H 2 + O 2 -> 2H 2 O H O H O 4 2 4 2 2 H 2 + O 2 -> 2H 2 O H O H O 4 2 4 2
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1. CH 4 + O 2 CO 2 + H 2 O C – 1 H – 4 O – 2 C– 1 O – 3 H – 2 Not balanced C – 1 H – 4 O – 2 C– 1 O – 3 H – 2 Not balanced
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2 Na + I 2 2 NaI 2. 2 Na + I 2 2 NaI Na I Na I 2 2 2 2 balanced Na I Na I 2 2 2 2 balanced
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N 2 + O 2 N 2 O 3. N 2 + O 2 N 2 O N O N O 2 2 2 1 Not balanced N O N O 2 2 2 1 Not balanced
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2KI + Cl 2 KCl + I 2 4. 2KI + Cl 2 KCl + I 2 K I Cl K I Cl 2 2 2 1 2 1 Not balanced K I Cl K I Cl 2 2 2 1 2 1 Not balanced
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S + O 2 SO 3 5. S + O 2 SO 3 S O S O 1 2 1 3 Not balanced S O S O 1 2 1 3 Not balanced
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Controlling Chemical Reactions Most chemical reactions involve a transfer of energy. Some reactions release energy. Some reactions absorb energy. Release energy: exothermic reaction Absorb energy: endothermic reaction Most chemical reactions involve a transfer of energy. Some reactions release energy. Some reactions absorb energy. Release energy: exothermic reaction Absorb energy: endothermic reaction Melting ice cube Burning candle Ex othermic = energy ex its En dothermic = energy in
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Activation Energy… Energy needed to start or begin a reaction Enzymes and Catalysts can change the rate of a reaction…(ex. Enzyme in your saliva) Match used to start a fire. Energy needed to start or begin a reaction Enzymes and Catalysts can change the rate of a reaction…(ex. Enzyme in your saliva) Match used to start a fire.
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