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Chemistry Chapter 8 Chemical Equations

Chemistry Chapter 8 Chemical Equations. Balancing Formula Equations. What is a Chemical Reaction?. A chemical reaction occurs when two or more substances are changed into different substances.

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Chemistry Chapter 8 Chemical Equations

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  1. Chemistry Chapter 8 Chemical Equations Balancing Formula Equations

  2. What is a Chemical Reaction? • A chemical reaction occurs when two or more substances are changed into different substances.

  3. What is a Chemical Equation?A chemical equation represents, with symbols and formulas, the identities and relative molecular or molar amounts of the reactants and products in a chemical reaction.

  4. Indications of a Chemical Reaction • Evolution of energy as heat and light. • Production of a gas. • Formation of a precipitate. • Color change.

  5. Characteristics of Chemical Equations • The equation must represent known facts. • The equation MUST contain the correct formulas for the reactants and products. • The Law of Conservation of Mass must be satisfied. We can use coefficients to satisfy this law. *coefficients- a small whole number that appears in front of a formula in a chemical equation

  6. Word & Formula Equations • word equation- an equation in which the reactants and products of a reaction are represented by words • formula equation- represents the reactants and products of a chemical reaction by their symbols & formulas • balanced formula equation- uses coefficients to allow conservation of mass

  7. Examples of the Types of Equations word equation- iron II phosphate reacts with aluminum nitrate to produce iron II nitrate and aluminum phosphate formula equation- Fe3(PO4)2 + Al(NO3)3 Fe(NO3)2 + AlPO4 balanced formula equation- Fe3(PO4)2 + 2 Al(NO3)3 3 Fe(NO3)2 + 2 AlPO4

  8. Symbols Used in Chemical Equations  yields (s) solid (l) liquid (aq) aqueous (g) gas

  9. Diatomic Elements • There are seven common elements that are called the “diatomic elements”. Whenever they are pure elements and appear alone (NOT in a compound) in an equation, their symbol contains two atoms rather than one. They include: hydrogen (H2) oxygen (O2) nitrogen (N2) fluorine (F2) chlorine (Cl2) bromine (Br2) iodine (I2) A simple mnemonic is “halogens HON”.

  10. Practice Problems • Do practice problems #1, #2, & #3 on page 268 of the textbook.

  11. Practice Problem 1 page 268 1a) Ca (s) + S (s) CaS (s) already balanced 1b) H2 (g) + F2 (g)  HF (g) H2 (g) + F2 (g)  2 HF (g) balanced 1c) Al (S) + ZnCl2 (aq)  Zn (s) + AlCl3 (aq) 2 Al(S) + 3 ZnCl2 (aq)  3 Zn(s) + 2 AlCl3(aq)

  12. Practice Problem #2 page 268 2a) CS2(l) + O2(g)  CO2(g) + SO2(g) liquid carbon disulfide reacts with oxygen gas to produce carbon dioxide gas and sulfur dioxide gas 2b) NaCl(aq) + AgNO3(aq)  NaNO3(aq) + AgCl(s) aqueous sodium chloride reacts with aqueous silver nitrate to yield aqueous sodium nitrate and solid silver chloride

  13. Practice problem #3 page 268 • N2H4 + O2 N2 (g) + H2O N2H4 + O2 N2 (g) + 2 H2O

  14. Significance of a Chemical Equation • The coefficients of a chemical reaction indicate relative, not absolute, amounts of reactants and products. • The relative masses of the reactants and products of a chemical reaction can be determined from the reaction’s coefficients. • The reverse reaction for a chemical equation has the same relative amounts of substances as the forward reaction.

  15. Rules for Balancing Chemical Equations • Identify the names of the reactants and products and write a word equation. • Write a formula equation by substituting correct formulas for the names of the reactants and products. • Using coefficients, balance the formula equation according to the law of conservation of mass. • Balance the different types of atoms one at a time. • First balance atoms of elements that appear only once on each side. • Balance polyatomic ions that appear on both sides as single units. • Balance H and O atoms after atoms of other elements have been balanced. • Count atoms to be sure the equation is balanced.

  16. Balancing a Formula Equation • hydrogen gas reacts with chlorine gas to produce hydrogen chloride gas • _?_ H2(g) + _?_ Cl2(g) _?_ HCl(g) • H2(g) +Cl2(g)  2 HCl(g)

  17. Practice #1- Balance the following formula equations. __CaF2 + __Na2S  __CaS + __ NaF __FeS + __ AlPO4  __Fe3(PO4)2 + __Al2S3 __Na + __Cl2  __NaCl __H2 + __O2  __H2O __C2H4 + __O2  __CO2 + __H2O __HBr + __NaOH  __NaBr + __H2O __Na2SO4 + __AlPO4  __Na3PO4 + __Al2(SO4)3 __N2 + __O2  __N3O7 __FePO4 + __CaSO4  __Fe2(SO4)3 + __Ca3(PO4)2 __CuBr2 + __NaF  __CuF2 + __NaBr

  18. Balanced Formula Equation __CaF2 + __Na2S  __CaS + __ NaF CaF2 + Na2S  CaS + 2 NaF 1:1:1:2 __FeS + __ AlPO4  __Fe3(PO4)2 + __Al2S3 3 FeS + 2 AlPO4  Fe3(PO4)2 + Al2S3 3:2:1:1 __Na + __Cl2  __NaCl 2 Na + Cl2  2 NaCl 2:1:2 __H2 + __O2  __H2O 2 H2 + O2  2 H2O 2:1:2 __C2H4 + __O2  __CO2 + __H2O C2H4 + 3 O2  2 CO2 + 2 H2O 1:3:2:2

  19. Practice __HBr + __NaOH  __NaBr + __H2O HBr + NaOH  NaBr + H2O 1:1:1:1 __Na2SO4 + __AlPO4  __Na3PO4 + __Al2(SO4)3 3 Na2SO4 + 2 AlPO4  2 Na3PO4 + Al2(SO4)3 3:2:2:1 __N2 + __O2  __N3O7 3 N2 + 7 O2  2 N3O7 3:7:2 __FePO4 + __CaSO4  __Fe2(SO4)3 + __Ca3(PO4)2 2 FePO4 + 3 CaSO4  Fe2(SO4)3+ Ca3(PO4)2 2:3:1:1 __CuBr2 + __NaF  __CuF2 + __NaBr CuBr2 + 2 NaF  CuF2 + 2 NaBr 1:2:1:2

  20. Practice Problems • Do the following practice problems from the textbook: practice #1 & #2 on page 272 practice #1 (a, b, c) on page 274 section review #2, #3, #4, & #5 on page 274

  21. Practice Problems page 272 1a) Mg + HCl MgCl2 + H2 Mg + 2 HCl  MgCl2 + H2 1b) HNO3 (aq) + Mg(OH)2 (s)  Mg(NO3)2 (aq) + H2O (l) 2 HNO3 (aq) + Mg(OH)2 (s)  Mg(NO3)2 (aq) + 2 H2O (l) 2) Ca(s) + H2O(l)  Ca(OH)2 (aq) + H2 (g) Ca(s) + 2 H2O(l)  Ca(OH)2 (aq) + H2 (g)

  22. Practice Problems page 274 1a) Na (s) + Cl2 (g)  NaCl (s) 2 Na (s) + Cl2 (g)  2 NaCl (s) 1b) Cu (s) + AgNO3 (aq)  Cu(NO3)2 (aq) + Ag (s) Cu (s) + 2 AgNO3 (aq)  Cu(NO3)2 (aq) + 2 Ag (s) 1c) Fe2O3 (s) + CO (g)  Fe (s) + CO2 (g) Fe2O3 (s) + 3 CO (g)  2 Fe (s) + 3 CO2 (g)

  23. Section Review page 274 2) H2SO4 (aq) + NaOH (aq)  Na2SO4 (aq) + H2O (l) H2SO4 (aq) + 2 NaOH (aq)  Na2SO4 (aq) + 2 H2O (l) 3a) solid potassium plus liquid water produce aqueous potassium hydroxide and hydrogen gas 3b) solid iron metal plus chlorine gas yields solid iron (III) chloride 4) H2S (g) + O2(g) SO2 (g) + H2O (g) 2 H2S (g) + 3 O2(g) 2 SO2 (g) + 2 H2O (g)

  24. Section Review page 274 5) VO + Fe2O3  V2O5 + FeO 2 VO + 3 Fe2O3  V2O5 + 6 FeO

  25. QUIZ #1- Balancing chemical equations Balance the following formula equations. 1- ___C3H8 + ___O2 ___CO2 + ___H2O 2- ___Al2(SO4)3 + ___Fe3(PO4)2  ___AlPO4 + ___FeSO4 3- ___Na + ___Cl2  ___NaCl 4- ___N2 + ___O2  ___N3O7 5- ___NaNO3 + ___Al2(CO3)3  ___Na2CO3 + ___Al(NO3)3

  26. Types of Chemical Reactions synthesis reaction- also known as a composition reaction, two or more substances combine to form a new compound. A + X  AX Could be called the ”Boy Meets Girl” reaction.

  27. Types of Chemical Reactions decomposition reaction- a single compound undergoes a reaction that produces two or more simpler substances. AX  A + X The “Boy Loses Girl” reaction.

  28. Types of Chemical Reactions single-displacement reaction- also known as a replacement reaction, one element replaces a similar element in a compound. A + BX  AX + B The “Boy Loses Girl to Best Friend” reaction.

  29. Types of Chemical Reactions double-displacement reaction- also known as a double replacement reaction, the ions of two compounds exchange places in an aqueous solution to form two new compounds. AX + BY  AY + BX The “Best Friends Trade Girlfriends” Reaction.

  30. Types of Chemical Reactions combustion reaction- a substance combines with oxygen, releasing a large amount of energy in the form of light and heat A + O2 AO + fire The “Where There’s Smoke There’s Fire” reaction.

  31. Reaction Types Summary Synthesis A + X  AX Decomposition AX  A + X Single Displacement A + BX  AX + B Double Replacement AX + BY  AY + BX Combustion A + O2  AO + fire

  32. QUIZ #2- Balance the following formula equations then identify the reaction type. __Na + __Br2 __NaBr reaction type= __Fe2O3 __Fe + __O2 reaction type= __CuI + __F2  __CuF + __I2 reaction type= __FeSO4 + __Ca3(PO4)2  __Fe3(PO4)2 + __CaSO4 reaction type= __C4H8 + __O2  __CO2 + __H2O (fire) reaction type=

  33. QUIZ #2- Balance the following formula equations then identify the reaction type. __Na + __Br2 __NaBr 2 Na + Br2 2 NaBr synthesis (composition) __Fe2O3 __Fe + __O2 2 Fe2O3 4 Fe + 3 O2 decomposition __CuI + __F2  __CuF + __I2 2 CuI + F2  2 CuF + I2 single replacement (single displacement) __FeSO4 + __Ca3(PO4)2  __Fe3(PO4)2 + __CaSO4 3 FeSO4 + Ca3(PO4)2  Fe3(PO4)2 + 3 CaSO4 double replacement (double displacement) __C4H8 + __O2  __CO2 + __H2O (fire) C4H8 + 6 O2  4 CO2 + 4 H2O (fire) combustion

  34. Types of Chemical Reactions synthesis reaction- also known as a composition reaction, two or more substances combine to form a new compound. A + X  AX

  35. Journal Investigation- Synthesis Reaction • Get a strip of magnesium ribbon and an iron crucible from the front. • Roll the magnesium strip into a loose ball. • Weigh & record the mass of the magnesium & crucible on a scale. • Heat the crucible and magnesium using your burner until the magnesium begins to glow. Turn off the burner. • Allow the crucible to cool at least five minutes. • Weigh and record the new mass of the crucible & magnesium oxide product. • Add three or four drops of tap water to the crucible. Waft the gas produced to attempt to smell the odor of ammonia.

  36. Safety Precautions Burner & equipment become very hot. DO NOT touch. Handle with crucible tongs. Eye protection MUST be worn due to possible sparks in the crucible. Safety apron is to be worn to protect skin & clothing. Use a wafting technique when trying to detect ammonia smell. Rinse & dry the cool crucible after lab is finished.

  37. Journal Investigation- Synthesis ReactionANALYSIS • Using the recorded masses, show how this proves a synthesis reaction occurred. • The magnesium (Mg) combined with oxygen (O2) in the air to form a magnesium oxide (MgO) product. Write a balanced formula equation for this reaction. • When you added water, you should have smelled ammonia (NH3). The formula equation for this reaction would be Mg3N2 + H2O  Mg(OH)2 + NH3. Balance this formula equation. • Where did the nitrogen come from to form the Mg2N3 as another product of this synthesis reaction?

  38. Types of Chemical Reactions decomposition reaction- a single compound undergoes a reaction that produces two or more simpler substances. AX  A + X

  39. Lab Investigation- Decomposition Reaction • Get a test tube with 5 – 10 mL of fresh hydrogen peroxide (H2O2) from the rack in the front of the room. • Add a match-head size amount of manganese dioxide (MnO2) to the test tube to act as a catalyst (a substance that speeds up a reaction without becoming part of it). • Observe the hydrogen peroxide for signs of a chemical reaction. • While the reaction is still taking place, set the end of a wooden splint on fire then blow it out. • While the splint is still glowing, lower it into the top of the test tube without touching the liquid. Observe the result. You can repeat this step several times until the reaction in the test tube stops.

  40. Lab Investigation- Decomposition ReactionANALYSIS • Use your textbook to find the definition of a catalyst. Write the definition in the log. • What was the indication in the test tube that a chemical reaction was taking place? • Hydrogen peroxide decomposed into oxygen gas and liquid water. Write the balanced formula equation for this reaction. • What test was used to demonstrate that oxygen gas was a product of the reaction? • Write a balanced formula equation for the reaction between the carbon in the wood and the oxygen gas being produced. What type of chemical reaction is this?

  41. Types of Chemical Reactions single-displacement reaction- also known as a replacement reaction, one element replaces a similar element in a compound. A + BX  AX + B

  42. Lab Investigation- Single Replacement Reaction • Get a small beaker with 20-25 mL. of silver nitrate (AgNO3). BE CAREFUL- silver nitrate will cause burn on your skin & clothing. • Record in your journal the color of the silver nitrate solution. • Get a penny from your instructor. • Gently lower the penny into the beaker of silver nitrate making sure there is no splash. • Record observation of the penny in your journal for 10 minutes at 1 minute intervals. • Use a piece of tape to identify your beaker & penny. Place the beaker in the fume hood overnight. • Record your observations after 24 hours. Be sure to include the color of the liquid in the beaker.

  43. Lab Investigation- Single Replacement ReactionANALYSIS • What were the indications that a chemical reaction had taken place? • What were the products of the single replacement reaction between copper (Cu) and silver nitrate (AgNO3)? (Assume the product contains the copper I ion.) • Write the balanced formula equation for the reaction between copper and silver nitrate. • Based on your observations, which element, copper or silver would appear higher on an activity series of metals? Why?

  44. Types of Chemical Reactions double-displacement reaction- also known as a double replacement reaction, the ions of two compounds exchange places in an aqueous solution to form two new compounds. AX + BY  AY + BX

  45. Lab Investigation- Double Replacement Reaction • Get a test tube with 5 mL. of silver nitrate (AgNO3). BE CAREFUL- silver nitrate will cause burns on your skin & clothing. • Record in your journal the color of the silver nitrate solution. • Get a test tube of sodium chloride (NaCl) solution. Record your observations of the solution. • Gently pour the sodium chloride into the test tube of silver nitrate making sure there is no splash. • Record your observation of the mixtures of the two aqueous solutions. • Take the test tubes to the front for disposal.

  46. Lab Investigation- Double Replacement ReactionANALYSIS • What were the indications that a chemical reaction had taken place? • What were the products of the double replacement reaction between sodium chloride (NaCl) and silver nitrate (AgNO3)? • Which of these products is the precipitate? • Write the balanced formula equation for the reaction between aqueous sodium chloride and aqueous silver nitrate.

  47. Types of Chemical Reactions combustion reaction- a substance combines with oxygen, releasing a large amount of energy in the form of light and heat A + O2 AO + fire

  48. Just for Fun- The Kandy Killer This will be a demonstration ONLY. • We will be heating potassium chlorate (KClO3). This will cause it to undergo a decomposition reaction that produces potassium chloride and oxygen. • A glowing splint will be used to confirm that oxygen is being produced. • Candy will be dropped into the test tube. A rapid chemical reaction should be seen. YEA!!!

  49. Practice Problems section review problems: #1 through #5 on page 284 of the textbook.

  50. Section Review page 284 1- List 5 types of reactions identified in this chapter. synthesis decomposition single displacement (replacement) double displacement (replacement) combustion 2a- N2 + 3H2 2 NH3 synthesis b- 2Li + 2H2O  2LiOH + H2 single displacement c- 2NaNO3  2NaNO2 + O2 decomposition d- 2C6H14 + 19O2  12CO2 + 14H2O combustion

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