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Unit 10: Chemical Equations

Unit 10: Chemical Equations. Chapter Objectives. 1. To learn to write chemical equations 2. To correctly interpret chemical equations 3. To balance chemical equations. Chapter Objectives. 4. To classify chemical reactions 5. To predict products of chemical reactions

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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

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