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Unit 10: Chemical Equations

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  1. Unit 10:Chemical Equations

  2. Chapter Objectives • 1. To learn to write chemical equations • 2. To correctly interpret chemical equations • 3. To balance chemical equations

  3. Chapter Objectives • 4. To classify chemical reactions • 5. To predict products of chemical reactions • 6. To write ionic and net ionic equations

  4. Chemical Reactions • In a chemical reaction, substances join together to form new substances • The original substances present are called REACTANTS • The new substances formed are called PRODUCTS

  5. Discussion of Chemical Reactions • The general form of an equation is: • Reactants  Products • The  is read as “yields” or “reacts to produce”

  6. Discussion of Chemical Reactions • A + B  C • Substance “A” and “B” react to produce substance “C”

  7. Additional Symbols in Chemical Reactions • + used to separate reactants or products • (s) means chemical is in solid state • (l) means chemical is in liquid state

  8. Additional Symbols in Chemical Reactions • (g) means chemical is in gas state • (aq) means chemical is dissolved in water • *See Table 10-1 in book (page 278)

  9. Other Symbols •  means something is added to the reaction • Usually this is heat • Pt means a catalyst (Pt) is added

  10. Skeleton Equations • Skeleton (Formula) Equation- the rough form of an equation • It only shows the framework for the chemical reaction

  11. Write Skeleton Equations • Sodium metal reacts with Oxygen gas to form solid Sodium Oxide • Solid sulfur reacts with Fluorine gas to form gaseous Sulfur Hexafluoride when heated • Nitrogen reacts with Hydrogen to form Ammonia (NH3) gas. Heat is required.

  12. Review-Write Skeleton Equations • 1. Magnesium metal reacts with Chlorine to form solid Magnesium Chloride. • 2. Aqueous Silver Nitrate reacts with aqueous Sodium Chloride to form solid Silver Chloride and aqueous sodium nitrate

  13. Law of Conservation of Mass • The Law of Conservation of Mass states that mass is neither created or destroyed in a chemical reaction • Because of this Law, it is necessary to balance chemical equations

  14. Balancing Chemical Equations • In balanced chemical equations, each side of the equation has the same number of atoms of each element • Coefficientsare used to balance chemical equations

  15. Question • What is the difference between a coefficient and subscript? • Coefficients are written before the formulas • Subscripts are part of the formula • Never use SUBSCRIPTS to balance an equation!!

  16. Rules for Balancing Equations • 1. Determine the correct formulas for the reactants and products • 2. Write the formulas for the reactants on the left side of the arrow. Write the formulas for the products on the right side of the arrow

  17. Rules Continued • 3. Count the number of atoms of each element present on both sides of the equation • 4. Balance the elements one at a time by placing coefficients in front of the formula. • 5. Check to make sure each atom is balanced

  18. Additional Rules • 6. Check to make sure that all coefficients are in the lowest possible ratio • **If no coefficient is written, the coefficient is assumed to be “1”

  19. Examples • Balance the following • H2 (g) + O2 (g)  H2O (l) • Na (s) + Br2 (g)  NaBr (aq) • AgNO3 (aq) + Cu(s)  Cu(NO3)2 (aq) + Ag(s)

  20. Classwork • Complete Worksheet

  21. Review-balance the following • 1. Fe + O2  Fe2O3 • 2. Al2O3 + H2 Al + H2O

  22. Quiz Review - Balance • 1. FeCl3 + NaOH  Fe(OH)3 + NaCl • 2. CuCl2 + NaI  CuI2 + NaCl • 3. H2O2  H2O + O2

  23. QUIZ • 1) C6H6 + O2 CO2 + H2O • 2) Mg + O2  MgO

  24. QUIZ REVIEW • 1. Solid sulfur reacts with gaseous fluorine to produce aqueous sulfur hexafluoride • 2.Magnesium metal reacts with chlorine gas to make solid magnesium chloride

  25. Additional Questions • Pb(NO3)2 + 2 NaOH  Pb(OH)2 + 2 NaNO3 • How many oxygen atoms are on the reactant side? • How many oxygen atoms are in 2 NaNO3?

  26. Balancing Equations -Determining Formulas • To Balance Equations, you must remember how to write correct chemical formulas

  27. Example • Write the balanced equation for solid aluminum reacting with oxygen gas to form solid aluminum oxide • **Remember that the diatomic elements (Mr. BrINClHOF) appear with a subscript of two when alone

  28. Additional Examples • 1. Carbon reacts with Chlorine to form Carbon Tetrachloride • 2. Magnesium metal reacts with solid Zinc (II) Carbonate to form solid Magnesium Carbonate and Zinc metal • 3. Nitrogen gas reacts with Hydrogen gas to form Ammonia (NH3) gas

  29. Types of Reactions • There are five general types of reactions: • Synthesis • Decomposition • Single Displacement • Double Displacement • Combustion

  30. Synthesis Reactions • Synthesis reactions are also called combination reactions • A synthesis reaction occurs when two substances combine to form a new compound

  31. Synthesis Reaction Continued • The general form of a synthesis reaction is: • A + X AX • Substance “AX” is the only substance formed

  32. Examples of Synthesis Reactions • 2 Mg (s) + O2 (g)  2 MgO (s) • Fe (s) + Cl2 (g)  FeCl2 (s) • U (s) + 3 F2 (g)  UF6 (g)

  33. Decomposition Reaction • In decomposition reactions, one substance breaks down (decomposes) into two or more simpler substances

  34. Decomposition Reactions Cont. • General Form of Decomposition Reaction: • AX A + X

  35. Examples of Decomposition Reactions • 2 HgO (s)  2 Hg (l) + O2 (g) • Ca(OH)2  CaO (s) + H2O (g) • H2SO4 (aq)  SO3 (g) + H2O (l)  

  36. Write Correct Balance Equations • 1. The synthesis of KCl • 2. The decomposition of magnesium oxide • 3. The decomposition of hydrogen peroxide (H2O2) into oxygen and water

  37. Write Correct Balance Chemical Equations for the following reactions • 1. The synthesis of barium fluoride • 2. The decomposition of Mg(OH)2 into magnesium oxide and water • 3. The decomposition of water

  38. Review-Write Balanced Equations • 1. Gaseous hydrogen reacts with gaseous chlorine to form aqueous hydrogen chloride • 2. Carbon monoxide gas reacts with gaseous oxygen to form solid carbon dioxide

  39. Write balanced equations • 1. The synthesis of Iron (III) oxide • 2. The decomposition of cobalt (IV) oxide • 3. The decomposition of calcium hydroxide into calcium oxide and water

  40. Write Balanced Equations • 1) Na + Cl2 • 2) HgCl2 • 3) Fe(OH)3

  41. Single Replacement Reaction • In a single replacement reaction (also called a displacement reaction), an element reacts with a compound • A + BX AX + B

  42. Examples of Single Replacement Reactions • Mg + Zn(NO3)2  Mg(NO3)2 + Zn • Mg + 2 AgNO3  Mg(NO3)2 (aq) + 2 Ag

  43. Rules for Single Replacement Reactions • Not all single replacement reactions occur • You can determine if a reaction will occur by knowing the activity series of metals (See Handout)

  44. Rules for Single Replacement • The activity series tell you if one metal can replace another metal in a reaction • The Activity Series is ordered • Any metal that is above another metal in the activity series WILL REPLACE the less reactive metal

  45. Li K Ca Na Mg Al Zn Fe Pb H* Cu Hg Ag Activity Series

  46. Predict if the following reactions will occur • 1. Fe + H2O • 2. Mg + LiNO3 • 3. Na + AgCl

  47. Write balanced equations for the following reactions • 1. Mg + O2 • 2. FeCl3 • 3. Fe + ZnO  • 4. Br2 + MgI2 

  48. Review • Predict the products and balance: • 1) Mg + O2 • 2) HCl  • 3) Na + H2SO4  • 4) Ag + ZnCl2 

  49. Double Displacement Reactions • In a double displacement reaction, two compounds react • The compounds swap elements with each other

  50. Double Displacement Cont • Compounds contain a positive and negative part • In a double displacement, the positive parts swap places with each other as do the negative parts