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Chapter 11 notes

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Chapter 11 notes

1. 1. Chapter 11 Chemical Reactions and Equations
2. 2. Word Equations • Recall that word equations can describe chemical reactions. • Reactants are written to the left of the arrow and products are written to the right of the arrow. • Recall how to name and write formulas from your flowchart. • A skeleton equation is the formulas of the reactants and products without the amounts included.
3. 3. Balancing Chemical Equations • Skeleton equations do not require amounts but in order to use actual equations in chemistry, a balanced equation with amounts must be written.
4. 4. Law of Conservation of Mass • Chemical reactions must obey the Law of Conservation of Mass. • Reactants must equal the products in amount and mass. • A balanced chemical equation compares the amounts of reactants to products.
5. 5. An Example…. • We need two wheels to make a toy car. • They are sold only in twos. • Each toy car has one car body (Cb) and 4 wheels are necessary. (W4) • What would be our balanced chemical equation for the toy car?
6. 6. Building a Toy Car
7. 7. Building a Tricycle…. • Again, we need one trike body (Tb) but a tricycle has 3 wheels (W3) and the wheels only come in packages of two. (W2) • How many orders of each tricycle should be make so there are no leftover parts? • Write a balanced “chemical” equation.
8. 8. Building Tricycle
9. 9. Tips and Tricks… • If there is a polyatomic ion on both sides of the equation, keep it together and balance it as one atom. • Balance the more complicated compounds first. • The elements that are by themselves should be balanced last. • Sometimes it is helpful to create a chart below the equation to keep track of the numbers. • If you have a word equation, write the skeleton equation first, then balance.
10. 10. LET’S PRACTICE! • Balance the equations. • AgNO3 + H2S Ag2S + HNO3 • Zn(OH)2 + H3PO4 Zn3(PO4)2 + H2 O • Iron(III) chloride + calcium hydroxide iron(III) hydroxide +
11. 11. ANSWERS • Balance the equations. • 2AgNO3 + H2S Ag2S + 2HNO3 • 3Zn(OH)2 + 2H3PO4 Zn3(PO4)2 + 6H2O • 2FeCl3 + 3Ca(OH)2 2Fe(OH)3 + 3CaCl2
12. 12. Vocabulary Cards • Skeleton equation • Reactants • Products • Law of Conservation of Mass
13. 13. SUM IT UP! • Write the balanced chemical equation for the following word equation. • Hydrogen + sulfur  hydrogen sulfide
14. 14. Types of Chemical Reactions • There are 5 general types of reactions. • Occasionally, a reaction may fit equally into two categories. • Identification is useful to help determine and predict the products.
15. 15. Combination Reactions • It is also called a synthesis reaction. • Two or more substances combine to create a single new substance. • Mg + O2  MgO • K + Cl2  KCl • Balance these equations!
16. 16. Decomposition Reactions • A single compound breaks down into two or more simpler products. • HgO  Hg + O2 • H2O H2 + O2 • Balance these equations!
17. 17. Single-Replacement Reaction • One element replaces a second element in a compound. • Requires the activity series to determine if the reaction will occur. • The element that is higher up on the series will replace any lower elements. • A halogen (group 7) can replace any other halogen providing that it is higher up on the periodic table. • If a reaction doesn’t occur, write NR for no reaction.
18. 18. Single-Replacement Reactions • K + H2O  KOH + H2 • Zn + Cu(NO3)2  Cu + Zn(NO3)2 • Br2 + NaI  NaBr + I2 • Br2 + NaCl  NR • Balance these equations!
19. 19. Double-Replacement Reactions • Sometimes when two solutions are mixed, nothing happens. • Other times, the ions in the two solutions react. • In these types of reactions, the two metal (positive) cations switch places with each other. • Occasionally, a precipitate will form or a gas will be generated. • Sometimes, both products are aqueous so you won’t see anything different
20. 20. Double-Replacement Reactions • Na2S + Cd(NO3)2  CdS + NaNO3 • NaCN + H2SO4  HCN + Na2SO4 • Ca(OH)2 + HCl  CaCl2 + H2O • Balance these equations!
21. 21. Combustion Reactions • This is a chemical change that takes place when a compound (usually a hydrocarbon) reacts with oxygen (O2) and produces carbon dioxide, water and usually energy in the form of heat and/or light. • C8H18 + O2  CO2 + H2O • When balancing, these numbers are usually high.
22. 22. Vocabulary Cards • Combination/Synthesis Reaction • Decomposition Reaction • Single-Replacement Reaction • Double-Replacement Reaction • Combustion Reaction
23. 23. SUM IT UP Write the balanced chemical reaction for the decomposition of aluminum oxide.
24. 24. Combination or synthesis reaction
25. 25. Single- Replacement Reaction
26. 26. Decomposition Reaction
27. 27. Double- Replacement Reaction
28. 28. Combination or Synthesis Reaction
29. 29. Single- Replacement Reaction
30. 30. Double-Replacement Reaction
31. 31. Decomposition Reaction
32. 32. Double Replacement reaction
33. 33. Reaction in Aqueous Solution • Your world is water-based. • Most reactions take place in water. • Most equations can show the reactions between compounds but do not show how the compounds behave when dissolved in water. • They actually separate into the various ions when in aqueous solution. • You can use these ions to write a complete ionic equation. • If the ion remains unchanged on both sides of the equation, it is called a spectator ion. • The spectator ion doesn’t participate in the reaction directly and can be cancelled out. • The resulting equation is called the net ionic equation. • Remember, the resulting equation must be balanced.
34. 34. Net Ionic Equations • A net ionic equation shows only those particles involved in the reaction and is balanced with respect to both mass and charge. • Pb (s) + 2Ag+ (aq)  2Ag (s) + Pb +2 (aq) • There are 2 Ag on both sides and +2 on both sides.
35. 35. Solubility • Soluble means it can dissolve in water or be aqueous. • There are rules to determine if something is soluble or not. • Page. 344 table 11.3 has the rules. • If something is soluble write (aq). • If it isn’t soluble or is insoluble, it is solid or (s). • Check the table for the rules.
36. 36. LET’S PRACTICE! • Balance this equation. • Ca+2 + OH- + H+ + PO4-3  Ca+2 + PO4-3 + H2O
37. 37. Answers • Balance this equation. • Ca+2 + 2OH- + 2H+ + PO4-3  Ca+2 + PO4-3 + 2H2O • First balance the charges, then balance the numbers of the types of atoms. • Both sides must have an equal charge.
38. 38. LET’S PRACTICE! • Write the complete and net ionic equations for: • Sodium hydroxide (aq) and phosphoric acid (aq) makes calcium phosphate and water. • Don’t forget to use your solubility rules.
39. 39. Answers • Write the complete and net ionic equations for: • Sodium hydroxide and phosphoric acid makes calcium phosphate and water. • 3Ca(OH)2 (aq) + 2H3PO4 (aq)  Ca3(PO4)2 (s) + 6H2O (l) • 3Ca +2 + 6OH- + 6H+ + 2PO4-3  3Ca+2 + 2PO4-3 + 6H2O • 6OH- + 6H+  6H2O • Reduce • OH- + H+  H2O
40. 40. Vocabulary Cards • Aqueous • Spectator ion • Complete ionic equations • Net ionic equations • Solubility
41. 41. SCIENCE SWAG • Create your own visual representation of the 5 types of chemical reactions we have studied. • Put them on a poster. • Due one week from today.
42. 42. POST IT UP Write a balanced net ionic equation for Lead(II) nitrate (aq) reacting with sulfuric acid (aq). Hint: It’s a double replacement reaction. I S! TH OT IG IN EE DH EL P!
43. 43. Excessive Cuteness!