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Reactions Making sense of chemical equations. Types of Reactions There are millions of reactions, and we cannot remember them all. Luckily they fall into.

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Presentation on theme: "Reactions Making sense of chemical equations. Types of Reactions There are millions of reactions, and we cannot remember them all. Luckily they fall into."— Presentation transcript:

1 Reactions Making sense of chemical equations

2 Types of Reactions There are millions of reactions, and we cannot remember them all. Luckily they fall into several categories. By looking at the reactants, we will: learn the 5 major types predict the products predict if they happen at all

3 Types of Reactions

4 Type 1: Combination Combination reactions happen when 2 elements combine to make a compound (also called synthesis). Examples: Ca + O 2 CaO SO 3 + H 2 O H 2 SO 4

5 Type 2: Decomposition

6 Type 3: Single Replacement In a single replacement reaction, one element replaces another. Reactants must be one element and one compound. Products will be a different element and a different compound.

7 Type 3: Single Replacement Examples: Na + KCl K + NaCl cation replaces cation F 2 + LiCl LiF + Cl 2 anion replaces anion

8 Type 4: Double Replacement Double replacement reactions occur when two elements replace each other in two different compounds. Reactants must be ionic compounds in aqueous solution. NaOH + FeCl 3 Fe(OH) 3 + NaCl The positive ions change places.

9 How to recognize each type: Look at the reactants: E + E = Combination C= Decomposition E + C= Single Replacement C + C= Double Replacement E = element; C = compound

10 Type 5: Combustion Combustion means add oxygen. Combustion reacts occur when compounds containing C, H, and O react with oxygen – usually called burning. If the combustion reaction is complete, the products will be CO 2 and H 2 O. If the combustion reaction is incomplete, the products will be CO (possibly just C) and H 2 O.

11 Predicting Products

12 Type 1: Combination We can predict the products, especially if the reactants are two elements: Mg + N 2 Al + Cl 2 Mg 3 N 2 AlCl 3

13 Type 1: Combination Practice: Ca + Cl 2 Fe + O 2 (assume Fe (II) in the product) Al + O 2

14 Type 1: Combination Watch out for: Some nonmetal oxides react with water to form acids: SO 2 + H 2 O H 2 SO 4 **This is what happens to make acid rain Some metallic oxides react with water to for bases: CaO + H 2 O Ca(OH) 2 **The hydroxide polyatomic ion indicates that the compound is a base.

15 Type 2: Decomposition

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17 Type 3: Single Replacement Metals will also replace other metals (and also hydrogen) Examples: K + AlN Zn + HCl Think of water at HOH: Metals replace the first H and then combine with OH -. Na + HOH

18 Type 3: Single Replacement We can even tell whether or not a single replacement reaction will happen: Because some metals are more active than others. More active replaces less active. There is a list on page 217 in the textbook. Called the Activity Series of Metals. Higher on the list replaces lower on the list.

19 Type 3: Single Replacement Rules: 1) Metals can replace other metals provided they are above the metal they are trying to replace. For example, zinc will replace lead. 2) Metals above hydrogen will replace hydrogen in acids. 3) Metals from sodium upward can replace hydrogen in water (HOH). Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead Hydrogen Bismuth Copper Mercury Silver Platinum Gold Higher activity Lower activity

20 Type 3: Single Replacement Practice: Fe + CuSO4 Pb + KCl Al + HCl

21 Type 3: Single Replacement Halogens have a similar activity series. Halogens can replace other halogens in compounds if they are above the halogen they are trying to replace. Examples: 2NaCl + F 2 MgCl 2 + Br 2 Fluorine Chlorine Bromine Iodine Higher Activity Lower Activity

22 Type 4: Double Replacement Double replacement reactions occur because of certain driving forces (or reasons). The reaction will only happen if one of the products: doesnt dissolve in water and forms a solid (a precipitate), or is a gas that bubbles out, or is a molecular compound (which will usually be water).

23 Complete and Balance assume all of the reactions take place CaCl 2 + NaOH CuCl 2 + K 2 S KOH + Fe(NO 3 ) 3 (NH 4 ) 2 SO 4 + BaF 2

24 How to recognize each type: Look at the reactants: E + E = Combination C= Decomposition E + C= Single Replacement C + C= Double Replacement E = element; C = compound

25 Practice H 2 + O 2 H 2 O Zn + H 2 SO 4 HgO KBr + Cl 2 AgNO 3 + NaCl Mg(OH) 2 + H 2 SO 3

26 Type 5: Combustion C 4 H 10 + O 2 (assume complete) C 4 H 10 + O 2 (incomplete) C 6 H 12 O 6 + O 2 (complete) C 8 H 8 + O 2 (incomplete)

27 SUMMARY Reactions come in 5 types. We can tell what type of reaction by looking at the reactants. Single replacement reactions occur based on activity series. Double replacement reactions occur if one product is: 1) a precipitate, 2) a gas, or 3) water (a molecular compound).


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