1 Chapter 7 Reactions in Aqueous Solutions

2 Types of Reactions Predicting the Products

3 Types of Reactions l There are millions of reactions. l Can’t remember them all l Fall into several categories. l We will learn 5 types. l Will be able to predict the products. l For some we will be able to predict whether they will happen at all. l Will recognize them by the reactants

4 Synthesis l the combination of 2 or more substances to form a compound l only one product A + B  AB

5 Synthesis H 2 (g) + Cl 2 (g)  2 HCl(g)

6 Al(s)+ Cl 2 (g)  AlCl 3 (s)2 3 2 B. Synthesis l Products: –ionic - cancel charges –covalent - hard to tell

7 Write and balance Ca + Cl 2  Fe + O 2  iron (II) oxide Al + O 2  l Remember that the first step is to write the formula l Then balance

8 Decomposition l a compound breaks down into 2 or more simpler substances l only one reactant AB  A + B

9 Decomposition 2 H 2 O(l)  2 H 2 (g) + O 2 (g)

10 KBr(l)  K(s) + Br 2 (l) 2 2 Decomposition l Products: –binary - break into elements –others - hard to tell

11 Decomposition Reactions l decompose = fall apart l one reactant falls apart into two or more elements or compounds. l NaCl Na + Cl 2 l CaCO 3 CaO + CO 2

12 Decomposition Reactions l Can predict the products if it is a binary compound l Made up of only two elements l Falls apart into its elements lH2OlH2O l HgO

13 Decomposition Reactions l If the compound has more than two elements you must be given one of the products l The other product will be from the missing pieces l NiCO 3 H 2 CO 3 (aq) 

14 Single Replacement l one element replaces another in a compound –metal replaces metal (+) –nonmetal replaces nonmetal (-) A + BC  B + AC

15 Single Replacement Cu(s) + 2AgNO 3 (aq)  Cu(NO 3 ) 2 (aq) + 2Ag(s)

16 Single Replacement l Products: –metal  metal (+) –nonmetal  nonmetal (-) –free element must be more active (check activity series) Na + KCl  K + NaCl F 2 + LiCl  LiF + Cl 2 Br 2 (l)+ NaCl(aq)  N.R.

17 Single Replacement l Exceptions we’ve missed along the way l Zinc, Zn, always forms a +2 ion doesn’t need parenthesis l ZnCl 2 is zinc chloride l Silver, Ag, always forms a +1 ion l AgCl is silver chloride

18 Single Replacement l Metals replace metals (and hydrogen) K + AlN  Zn + HCl  l Think of water as HOH l Metals replace one of the H, combine with hydroxide. Na + HOH 

19 #3 Single Replacement l We can tell whether a reaction will happen l Some are more active than other l More active replaces less active l Higher on the list replaces lower. l If the element by itself is higher, it happens, in lower it doesn’t

20 ACTIVITY SERIES

21 Single Replacement l Note the * l H can be replaced in acids by everything higher l Only the first 5 (Li - Na) react with water. Fe + CuSO 4  Pb + KCl  Al + HCl 

22 Single Replacement l What does it mean that Au And Ag are on the bottom of the list? l Nonmetals can replace other nonmetals l Limited to F 2, Cl 2, Br 2, I 2 l The order of activity is that on the table. l Higher replaces lower. F 2 + HCl  Br 2 + KCl 

23 AB + CD  AD + CB Double Replacement l ions in two compounds “change partners” l cation of one compound combines with anion of the other

24 Double Replacement Pb(NO 3 ) 2 (aq) + K 2 CrO 4 (aq)  PbCrO 4 (s) + 2KNO 3 (aq)

25 Double Replacement l Products: –switch negative ions –one product must be insoluble (check solubility table) NaOH + FeCl 3  l The positive ions change place. NaOH + FeCl 3  Fe +3 OH - + Na +1 Cl -1 NaOH + FeCl 3  Fe(OH) 3 + NaCl

26 Double Replacement l Two things replace each other. l Reactants must be two ionic compounds or acids. l Usually in aqueous solution

27 Double Replacement l Will only happen if one of the products –doesn’t dissolve in water and forms a solid –or is a gas that bubbles out. –or is a covalent compound usually water.

28 Complete and balance l 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 

29 How to recognize which type l Look at the reactants l E + E Combination l CDecomposition l E + CSingle replacement l C + CDouble replacement

30 Examples 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 

31 Last Type l Combustion l A compound composed of only C H and maybe O is reacted with oxygen l If the combustion is complete, the products will be CO 2 and H 2 O. l If the combustion is incomplete, the products will be CO and H 2 O.

32 A. Combustion CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 O(g) l the burning of any substance in O 2 to produce heat A + O 2  CO 2 + H 2 O

33 Na(s)+ O 2 (g)  C 3 H 8 (g)+ O 2 (g)  A. Combustion l Products: –contain oxygen –hydrocarbons form CO 2 + H 2 O CO 2 (g)+ H 2 O(g) Na 2 O(s) 4 2

34 Examples C 4 H 10 + O 2  (complete) C 4 H 10 + O 2  (incomplete) C 6 H 12 O 6 + O 2  (complete) C 8 H 8 +O 2  (incomplete)

Distinguish between complete an incomplete combustion,. 24. Write a balanced equation for the complete combustion of each of these compounds. a) acetic acid, HC 2 H 3 O 2 c) glycerol, C 3 H 8 O 3 b) decane, C 10 H 22 d) sucrose, C 12 H 22 O Write a balanced equation for the incomplete combustion of each of these compounds. a) glycerol, C 3 H 8 O 3 c) acetic acid, HC 2 H 3 O 2 b) glucose, C 6 H 12 O 6 d) acetylene, C 2 H 2

36 Chapter 7 Summary

37 An equation l Describes a reaction l Must be balanced because to follow Law of Conservation of Energy l Can only be balanced by changing the coefficients. l Has special symbols to indicate state, and if catalyst or energy is required.

38 Reactions l Come in 5 types. l Can tell what type they are by the reactants. l Single Replacement happens based on the activity series using activity series. l Double Replacement happens if the product is a solid, water, or a gas.

39 The Process l Determine the type by looking at the reactants. l Put the pieces next to each other l Use charges to write the formulas l Use coefficients to balance the equation. Homework