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Published byAbraham Ray Modified over 9 years ago
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8-2 Types of Chemical Reactions
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Combustion: A combustion reaction is when oxygen combines with a hydrocarbon to form water and carbon dioxide. These reactions are exothermic, meaning they produce heat. An example of this kind of reaction is the burning of napthalene: C 10 H 8 + 12 O 2 ---> 10 CO 2 + 4 H 2 O
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Synthesis (combination): A synthesis reaction is when two or more simple compounds combine to form a more complicated one. These reactions come in the general form of: A + B ---> AB One example of a synthesis reaction is the combination of iron and sulfur to form iron (II) sulfide: 8 Fe + S 8 ---> 8 FeS
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Decomposition: A decomposition reaction is the opposite of a synthesis reaction - a complex molecule breaks down to make simpler ones. These reactions come in the general form: AB ---> A + B One example of a decomposition reaction is the electrolysis of water to make oxygen and hydrogen gas: 2 H 2 O ---> 2 H 2 + O 2
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Single replacement (single displacement): This is when one element trades places with another element in a compound. These reactions come in the general form of: A + BC ---> AC + B One example of a single displacement reaction is when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas: Mg + 2 H 2 O ---> Mg(OH) 2 + H 2
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Double replacement (double displacement): This is when the anions and cations of two different molecules switch places, forming two entirely different compounds. These reactions are in the general form: AB + CD ---> AD + CB One example of a double displacement reaction is the reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate: Pb(NO 3 ) 2 + 2 KI ---> PbI 2 + 2 KNO 3
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Acid-base (water-forming): This is a special kind of double displacement reaction that takes place when an acid and base react with each other. The H+ ion in the acid reacts with the OH- ion in the base, causing the formation of water. Generally, the product of this reaction is some ionic salt and water: HA + BOH ---> H 2 O + BA One example of an acid-base reaction is the reaction of hydrobromic acid (HBr) with sodium hydroxide: HBr + NaOH ---> NaBr + H 2 O
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Follow this series of questions. When you can answer "yes" to a question, then stop! 1) Does your reaction have oxygen as one of it's reactants and carbon dioxide and water as products? If yes, then it's a combustion reaction 2) Does your reaction have two (or more) chemicals combining to form one chemical? If yes, then it's a synthesis reaction 3) Does your reaction have one large molecule falling apart to make several small ones? If yes, then it's a decomposition reaction 4) Does your reaction have any molecules that contain only one element? If yes, then it's a single replacement reaction 5) Does your reaction have water as one of the products? If yes, then it's an acid-base reaction 6) If you haven't answered "yes" to any of the questions above, then you've got a double replacement reaction
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List what type the following reactions are: 1) NaOH + KNO 3 --> NaNO 3 + KOH 2) CH 4 + 2 O 2 --> CO 2 + 2 H 2 O 3) 2 Fe + 6 NaBr --> 2 FeBr 3 + 6 Na 4) CaSO 4 + Mg(OH) 2 --> Ca(OH) 2 + MgSO 4 5) NH 4 OH + HBr --> H 2 O + NH 4 Br 6) Pb + O 2 --> PbO 2 7) Na 2 CO 3 --> Na 2 O + CO 2
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1) double replacement 2) combustion 3) single replacement 4) double replacement 5) acid-base (water forming) 6) synthesis 7) decomposition
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