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Chapter 11 Chemical Reactions.

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Presentation on theme: "Chapter 11 Chemical Reactions."— Presentation transcript:

1 Chapter 11 Chemical Reactions

2 All chemical reactions
have two parts Reactants - the substances you start with Products- the substances you end up with The reactants turn into the products. Reactants ® Products

3 In a chemical reaction The way atoms are joined is changed
Atoms aren’t created or destroyed. Can be described several ways In a sentence Copper reacts with chlorine to form copper (II) chloride. In a word equation Copper + chlorine ® copper (II) chloride

4 Symbols used in equations
Table 11.1 the arrow separates the reactants from the products Read “reacts to form” The plus sign = “and” (s) after the formula -solid (g) after the formula -gas (l) after the formula -liquid

5 Symbols used in equations
(aq) after the formula - dissolved in water, an aqueous solution. ­ used after a product indicates a gas (same as (g)) ¯ used after a product indicates a solid (same as (s))

6 Symbols used in equations
indicates a reversible reaction (More later) shows that heat is supplied to the reaction is used to indicate a catalyst used in this case, platinum.

7 What is a catalyst? A substance that speeds up a reaction without being changed by the reaction. Enzymes are biological or protein catalysts.

8 Skeleton Equation Uses formulas and symbols to describe a reaction
doesn’t indicate how many. All chemical equations are sentences that describe reactions.

9 Convert these to equations
Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form solid iron (II) chloride and hydrogen sulfide gas.

10 Convert these to equations
Nitric acid dissolved in water reacts with solid sodium carbonate to form liquid water and carbon dioxide gas and sodium nitrate dissolved in water.

11 The other way Fe(g) + O2(g) ® Fe2O3(s)

12 The other way Cu(s) + AgNO3(aq) ® Ag(s) + Cu(NO3)2(aq)

13 Balancing Chemical Equations

14 Balanced Equation Atoms can’t be created or destroyed
All the atoms we start with we must end up with A balanced equation has the same number of atoms of each element on both sides of the equation.

15 ® O + C O C O O C + O2 ® CO2 This equation is already balanced
What if it isn’t already?

16 ® C C O O C O C + C + O2 ® CO We need one more oxygen in the products.
Can’t change the formula, because it describes what actually happens

17 ® C C O C O C O + O Must be used to make another CO
But where did the other C come from? Must have started with two C 2 C + O2 ® 2 CO

18 Rules for balancing Write the correct formulas for all the reactants and products Count the number of atoms of each type appearing on both sides Balance the elements one at a time by adding coefficients (the numbers in front) Check to make sure it is balanced.

19 Never Change a subscript to balance an equation.
If you change the formula you are describing a different reaction. H2O is a different compound than H2O2 Never put a coefficient in the middle of a formula 2 NaCl is okay, Na2Cl is not.

20 Example R P H O 2 1 4 4 2 2 H2 + H2O O2 ® 2 H2 + H2O O2 ®
The equation is balanced, has the same number of each kind of atom on both sides Recount Changes the O Make a table to keep track of where you are at Need twice as much O in the product Also changes the H Need twice as much H in the reactant

21 Example R P 4 2 H 2 4 2 O 1 2 This is the answer 2 H2 + O2 ® 2 H2O
Not this 2 O 1 2

22 Examples CH4 + O2 ® CO H2O

23 Examples AgNO Cu ® Cu(NO3) Ag

24 Examples Al + N2 ® Al2N3

25 Examples P + O2 ® P4O10

26 Examples Na + H2O ® H2 + NaOH

27 Techniques If an atom appears more than once on a side, balance it last. If you fix everything except one element, and it is even on one side and odd on the other, double the first number, then move on from there. C4H10 + O2  CO2 + H2O

28 Predicting the Products
Types of Reactions Predicting the Products

29 Types of Reactions There are too many reactions to remember
Fall into categories. We will learn 5 types. Will be able to predict the products. For some we will be able to predict whether they will happen at all. Must recognize them by the reactants

30 #1 Combination Reactions
Combine - put together 2 elements, or compounds combine to make 1 compound. Ca +O2 ® CaO SO3 + H2O ® H2SO4 We can predict the products if they are two elements. Mg + N2 ®

31 Write and balance Ca + Cl2 ®

32 Write and balance Fe + O2 ® iron (II) oxide

33 Write and balance Al + O2 ®
Remember that the first step is to write the formula Then balance Also called synthesis reaction

34 Combining two compounds
If they tell you it is combination, you will make one product Two compounds will make a polyatomic ion. CO H2O → H2O + Cl2O7→

35 #2 Decomposition Reactions
decompose = fall apart one reactant falls apart into two or more elements or compounds. NaCl Na + Cl2 CaCO CaO + CO2

36 #2 Decomposition Reactions
Can predict the products if it is a binary compound Made up of only two elements Falls apart into its elements H2O

37 #2 Decomposition Reactions

38 #2 Decomposition Reactions
If the compound has more than two elements you must be given one of the products The other product will be from the missing pieces NiCO NiO + H2CO3(aq)® CO2 +

39 #3 Single Replacement One element replaces another
Reactants must be an element and a compound. Products will be a different element and a different compound. Na + KCl ® K + NaCl F2 + LiCl ® LiF + Cl2

40 Na + KCl ® K + NaCl Cl K Na

41 F2 + 2 LiCl ® 2 LiF + Cl2 Cl Li Li F F Cl Li Li

42 #3 Single Replacement Metals replace metals (and hydrogen)
Al + CuSO4 ® Zn + H2SO4 ® Think of water as HOH Metals replace one of the H, combine with hydroxide. Na + HOH ®

43 #3 Single Replacement We can tell whether a reaction will happen
Some are more active than other More active replaces less active There is a list on page 333

44 #3 Single Replacement There is a list on page 333
Higher on the list replaces lower. If the element by itself is higher, it happens, if element by itself is lower, it doesn’t

45 #3 Single Replacement Note the *
H can be replaced in acids by everything higher Only the first 4 (Li - Na) react with water.

46 #3 Single Replacement Al + HCl ®

47 #3 Single Replacement Fe + CuSO4 ®

48 #3 Single Replacement Pb + KCl ®

49 #3 Single Replacement Al + H2O ®

50 #3 Single Replacement What does it mean that Ag is on the bottom of the list?

51 #3 Single Replacement Nonmetals can replace other nonmetals
Limited to F2 , Cl2 , Br2 , I2 The order of activity is that on the table. Higher replaces lower. F2 + HCl ® Br2 + KCl ®

52 #4 Double Replacement Two things replace each other.
Reactants must be two ionic compounds or acids. Usually in aqueous solution NaOH + FeCl3 ® The positive ions change place. NaOH + FeCl3 ® Fe3+OH- + Na+Cl- NaOH + FeCl3 ® Fe(OH)3 + NaCl

53 3NaOH + FeCl3 ® Fe(OH)3 + 3NaCl

54 #4 Double Replacement 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. Polyatomic ions don’t change from side to side

55 Complete and balance assume all of the reactions take place.
CaCl2 + NaOH ® CuCl2 + K2S ® KOH + Fe(NO3)3 ®

56 Complete and balance KOH + Fe(NO3)3 ® H3PO4 + Ca(OH)2 ®

57 How to recognize which type
Look at the reactants E for element C for compound E + E Combination C Decomposition E + C Single replacement C + C Double replacement

58 Last Type Combustion A compound composed of only C H and maybe O is reacted with oxygen If the combustion is complete, the products will be CO2 and H2O. If the combustion is incomplete, the products will be CO and H2O. or just C and H2O. O2 will always be the second reactant

59 Examples Complete combustion of C4H10 Incomplete combustion of C4H10

60 Examples Complete combustion of C6H12O6 Incomplete combustion of C2H6O

61 Ionic Compounds and acids
Fall apart into ions when they dissolve That’s why they conduct electricity when dissolved. So when we write them as (aq) they are really separated NaCl(aq) is really Na+(aq) and Cl-(aq) K2SO4 (aq) is really K+(aq) and SO42-(aq)

62 Reactions in aqueous solutions
Many reactions happen in solution Makes it so the ions separate so they can interact. Solids, liquids, and gases are not separated, only aqueous

63 Complete Ionic Equation
Every aqueous compound is written as separate ions Solids, liquids and gases as whole compounds MgCl2(aq) + PbSO4(aq) → MgSO4(aq) + PbCl2(s) Is really Mg2+(aq) + Cl-(aq) + Pb2+(aq) + SO4(aq) → Mg2+(aq) + SO4(aq) + PbCl2(s)

64 Write the complete ionic equation for
FeBr3(aq) + KOH(aq) → KBr (aq) + Fe(OH)3(s) Fe3+(aq) Br-(aq) K+(aq) OH-(aq) K+(aq) Br-(aq) Fe(OH)3(s) + + + + +

65 Write the complete ionic equation for
CaCl2(aq) + MgSO4(aq) → CaSO4(s) + MgCl2(aq)

66 Write the complete ionic equation for
Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + HOH(l)

67 The complete ionic equation is
Fe3+(aq)+ Br-(aq) + K+(aq) +OH-(aq) → K+(aq) +Br-(aq) + Fe(OH)3(s) K+ and Br- don’t change. They are spectator ions Could be eliminated Fe3+(aq) +OH-(aq) →Fe(OH)3(s) This is what really changes

68 Net ionic equation Shows only those particles that change before and after. Eliminate spectator ions Needs to be balanced in terms of both mass and charge Fe3+(aq) +OH-(aq) →Fe(OH)3(s) Fe3+(aq) +3 OH-(aq) →Fe(OH)3(s)

69 Write the net ionic equation
HCl (aq) + Ba(OH)2 (aq) → BaCl2(s) + HOH (l)

70 Write the net ionic equation
Al + FeSO4(aq) → Al2(SO4)3(aq) + Fe

71 Write the net ionic equation
Cl2(s) + NaI(aq) → NaCl(aq) + I2(s)

72 Write the net ionic equation
K2CO3(aq) + MgI2(aq) → MgCO3(s) + KI(aq)

73 Net ionic equations Written for single and double replacement.

74 Predicting precipitates
Solids formed from aqueous solution. You can predict them if you know some general rules for solubility.

75 These things are soluble
Salts with alkali metals and ammonium Salts of nitrates and chlorates Salts of sulfates except Ag+, Pb2+, Hg22+, Ba2+, and Sr2+ Salts of chlorides except Ag+, Pb2+, and Hg22+

76 These things are insoluble
Carbonates, phosphates, chromates, sulfides, and hydroxides Unless they fall under rule # 1

77 Is it soluble? LiBr Ba(NO3)2 CaSO4 PbCl2 CaCO3 K2CO3 Cd(ClO3)2

78 Is there a reaction? For double replacement- has to make gas, solid or water. Water from an acid- H+ and a hydroxide- OH- makes HOH Solids- from solubility rules Exchange ions and see if something is insoluble

79 Is there a reaction? MgSO4 + NaOH → H2SO4 + KOH → K3PO4 + FeF3→

80 Chapter 7 Summary

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

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

83 The Process 1. Determine the type by looking at the reactants.
2. Put the pieces next to each other based on type 3. Use charges to write the formulas Elements get 2? 4. Use coefficients to balance the equation.

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