Tro3 lecture 07

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Tro3 lecture 07

  1. 1. Experiencing Chemical Change <ul><li>Chemical reactions are happening both around you and in you all the time. </li></ul><ul><li>Some are very simple, others are complex. </li></ul><ul><ul><li>In terms of the pieces—even the simple ones have a lot of interesting principles to learn from. </li></ul></ul><ul><li>Chemical reactions involve changes in the structures of the molecules, and many times we can experience the effects of those changes. </li></ul><ul><li>What are some examples of chemical reactions you experience? </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  2. 2. Chemical Reactions <ul><li>Reactions involve chemical changes in matter resulting in new substances. </li></ul><ul><li>Reactions involve rearrangement and exchange of atoms to produce new molecules. </li></ul><ul><ul><li>Elements are not transmuted during a reaction. </li></ul></ul><ul><ul><li>Atoms of different elements can combine to make new compounds. </li></ul></ul><ul><ul><li>Molecules can combine to make bigger molecules. </li></ul></ul><ul><ul><li>Molecules can decompose into smaller molecules or atoms. </li></ul></ul><ul><ul><li>Atoms can be exchanged between molecules or transferred to another molecule. </li></ul></ul><ul><ul><li>Atoms can gain or lose electrons, turning them into ions. </li></ul></ul><ul><ul><ul><li>Or changing the charge on ions that are already there. </li></ul></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  3. 3. Combustion Reactions <ul><li>Reactions in which O 2 is consumed by combining with another substance are called combustion reactions . </li></ul><ul><ul><li>Always release heat and/or other forms of energy. </li></ul></ul><ul><ul><li>Produce one or more oxygen-containing compounds. </li></ul></ul><ul><li>Combustion reactions are a subclass of oxidation – reduction reactions. </li></ul><ul><ul><li>aka redox reactions. </li></ul></ul><ul><ul><li>Involve the transfer of electrons between atoms. </li></ul></ul>Reactants  Products
  4. 4. Evidence of Chemical Reactions <ul><li>Look for evidence of a new substance. </li></ul><ul><li>Visual clues (permanent). </li></ul><ul><ul><li>Color change. </li></ul></ul><ul><ul><li>Precipitate formation. </li></ul></ul><ul><ul><ul><li>Solid that forms when liquid solutions are mixed. </li></ul></ul></ul><ul><ul><li>Gas bubbles. </li></ul></ul><ul><ul><li>Large energy changes. </li></ul></ul><ul><ul><ul><li>Container becomes very hot or cold. </li></ul></ul></ul><ul><ul><ul><li>Emission of light. </li></ul></ul></ul><ul><li>Other clues. </li></ul><ul><ul><li>New odor. </li></ul></ul><ul><ul><li>Whooshing sound from a tube. </li></ul></ul><ul><ul><li>Permanent new state. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  5. 5. Evidence of Chemical Change Tro's &quot;Introductory Chemistry&quot;, Chapter 7 Color Change Formation of Solid Precipitate Formation of a Gas Emission of Light Release or Absorption of Heat
  6. 6. Conservation of Mass <ul><li>Matter cannot be created or destroyed. </li></ul><ul><ul><li>Therefore, the total mass cannot change. </li></ul></ul><ul><ul><li>And the total mass of the reactants will be the same as the total mass of the products. </li></ul></ul><ul><li>In a chemical reaction, all the atoms present at the beginning are still present at the end. </li></ul><ul><ul><li>If all the atoms are still there, then the mass will not change. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  7. 7. Chemical Equations <ul><li>CH 4 and O 2 are the reactants, and CO 2 and H 2 O are the products. </li></ul><ul><li>The ( g ) after the formulas tells us the state of the chemical. </li></ul><ul><li>The number in front of each substance tells us the numbers of those molecules in the reaction. </li></ul><ul><ul><li>Called the coefficients . </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7 CH 4 ( g ) + 2 O 2 ( g )  CO 2 ( g ) + 2 H 2 O( g )
  8. 8. Example <ul><li>When magnesium metal burns in air, it produces a white, powdery compound magnesium oxide. </li></ul><ul><li>Write a skeletal equation </li></ul><ul><ul><li>Mg( s ) + O 2 ( g )  MgO( s ) </li></ul></ul><ul><li>Count the number of atoms on each side. </li></ul><ul><li>Mg( s ) + O 2 ( g )  MgO( s ) </li></ul><ul><li>1  Mg  1 </li></ul><ul><li>2  O  1 </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  9. 9. Example, Continued <ul><li>When magnesium metal burns in air, it produces a white, powdery compound magnesium oxide. </li></ul><ul><ul><li>Mg( s ) + O 2 ( g )  MgO( s ) </li></ul></ul><ul><li>Use factors as coefficients in front of the compound containing the element. </li></ul><ul><ul><li>We do not write 1 as a coefficient, its understood. </li></ul></ul><ul><li>Mg( s ) + O 2 ( g )  MgO( s ) </li></ul><ul><li>1  Mg  1 </li></ul><ul><li>1 x 2  O  1 x 2 </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7 2
  10. 10. Another Example <ul><li>Under appropriate conditions at 1000°C, ammonia gas reacts with oxygen gas to produce gaseous nitrogen monoxide and steam </li></ul><ul><li>write the skeletal equation </li></ul><ul><li>first in words </li></ul><ul><ul><li>identify the state of each chemical </li></ul></ul><ul><li>ammonia(g) + oxygen(g)  nitrogen monoxide(g) + water(g) </li></ul><ul><li>then write the equation in formulas </li></ul><ul><ul><li>identify diatomic elements </li></ul></ul><ul><ul><li>identify polyatomic ions </li></ul></ul><ul><ul><li>determine formulas </li></ul></ul><ul><li>NH 3 (g) + O 2 (g)  NO(g) + H 2 O(g) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  11. 11. <ul><li>Under appropriate conditions at 1000°C ammonia gas reacts with oxygen gas to produce gaseous nitrogen monoxide and steam </li></ul><ul><li>NH 3 (g) + O 2 (g)  NO(g) + H 2 O(g) </li></ul><ul><li>count the number of atoms of on each side </li></ul><ul><li>NH 3 (g) + O 2 (g)  NO(g) + H 2 O(g) </li></ul><ul><li>1  N  1 </li></ul><ul><li>3  H  2 </li></ul><ul><li>2  O  1 + 1 </li></ul>Another Example, Continued Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  12. 12. <ul><li>Under appropriate conditions at 1000°C ammonia gas reacts with oxygen gas to produce gaseous nitrogen monoxide and gaseous steam </li></ul><ul><li>NH 3 (g) + O 2 (g)  NO(g) + H 2 O(g) </li></ul><ul><li>pick an element to balance - H </li></ul><ul><ul><li>avoid element in multiple compounds on same side - O </li></ul></ul><ul><li>find least common multiple of both sides (6) </li></ul><ul><li>multiply each side by factor so it equals LCM </li></ul><ul><li>NH 3 (g) + O 2 (g)  NO(g) + H 2 O(g) </li></ul><ul><li>1  N  1 </li></ul><ul><li>3  H  2 </li></ul><ul><li>2  O  1 + 1 </li></ul>Another Example, Continued Tro's &quot;Introductory Chemistry&quot;, Chapter 7 2 x x 3
  13. 13. <ul><li>Under appropriate conditions at 1000°C ammonia gas reacts with oxygen gas to produce gaseous nitrogen monoxide and gaseous water </li></ul><ul><li>NH 3 (g) + O 2 (g)  NO(g) + H 2 O(g) </li></ul><ul><li>use factors as coefficients in front of compound containing the element </li></ul><ul><li>NH 3 (g) + O 2 (g)  NO(g) + H 2 O(g) </li></ul><ul><li>1  N  1 </li></ul><ul><li>2 x 3  H  2 x 3 </li></ul><ul><li>2  O  1 + 1 </li></ul>Another Example, Continued Tro's &quot;Introductory Chemistry&quot;, Chapter 7 2 3
  14. 14. <ul><li>Recount – N & O not balanced </li></ul><ul><li>2 NH 3 (g) + O 2 (g)  NO(g) + 3 H 2 O(g) </li></ul><ul><li>2  N  1 </li></ul><ul><li>6  H  6 </li></ul><ul><li>2  O  1 + 3 </li></ul><ul><li>and Repeat – attack the N </li></ul><ul><li>2 NH 3 (g) + O 2 (g)  2 NO(g) + 3 H 2 O(g) </li></ul><ul><li>2  N  1 x 2 </li></ul><ul><li>6  H  6 </li></ul><ul><li>2  O  1 + 3 </li></ul>Another Example, Continued Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  15. 15. <ul><li>Recount Again – Still not balanced and the only element left is O! </li></ul><ul><li>2 NH 3 (g) + O 2 (g)  2 NO(g) + 3 H 2 O(g) </li></ul><ul><li>2  N  2 </li></ul><ul><li>6  H  6 </li></ul><ul><li>2  O  2 + 3 </li></ul>Another Example, Continued Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  16. 16. <ul><li>and Repeat Again </li></ul><ul><ul><li>A trick of the trade - when you are forced to attack an element that is in 3 or more compounds – find where it is uncombined. You can find a factor to make it any amount you want, even if that factor is a fraction! </li></ul></ul><ul><ul><li>2 NH 3 (g) + ? O 2 (g)  2 NO(g) + 3 H 2 O(g) </li></ul></ul><ul><li>2  N  2 </li></ul><ul><li>6  H  6 </li></ul><ul><li>2  O  2 + 3 </li></ul><ul><ul><li>We want to make the O on the left equal 5, therefore we will multiply it by 2.5 </li></ul></ul><ul><li>2 NH 3 (g) + 2.5 O 2 (g)  2 NO(g) + 3 H 2 O(g) </li></ul><ul><li>2  N  2 </li></ul><ul><li>6  H  6 </li></ul><ul><li>2.5 x 2  O  2 + 3 </li></ul>Another Example, Continued
  17. 17. <ul><li>You can’t have a coefficient that isn’t a whole number. Multiply all the coefficients by a number to eliminate fractions </li></ul><ul><ul><li>If ?.5, then multiply by 2; if ?.33, then 3; if ?.25, then 4 </li></ul></ul><ul><li>{2 NH 3 (g) + 2.5 O 2 (g)  2 NO(g) + 3 H 2 O(g)} x 2 </li></ul><ul><li>4 NH 3 (g) + 5 O 2 (g)  4 NO(g) + 6 H 2 O(g) </li></ul><ul><li>4  N  4 </li></ul><ul><li>12  H  12 </li></ul><ul><li>10  O  4 + 6 </li></ul>Another Example, Continued Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  18. 18. Practice #1 <ul><li>When aluminum metal reacts with air, it produces a white, powdery compound called aluminum oxide. </li></ul><ul><ul><li>Reacting with air means reacting with O 2 : </li></ul></ul><ul><li>Aluminum( s ) + oxygen( g )  aluminum oxide( s ) </li></ul><ul><li>Al( s ) + O 2 ( g )  Al 2 O 3 ( s ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  19. 19. Practice #1, Continued <ul><li>When aluminum metal reacts with air, it produces a white, powdery compound called aluminum oxide. </li></ul><ul><ul><li>Reacting with air means reacting with O 2 : </li></ul></ul><ul><li>Aluminum( s ) + oxygen( g )  aluminum oxide( s ) </li></ul><ul><li>Al( s ) + O 2 ( g )  Al 2 O 3 ( s ) </li></ul><ul><li>4 Al( s ) + 3 O 2 ( g )  2 Al 2 O 3 ( s ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  20. 20. Practice #2, Continued <ul><li>Acetic acid reacts with the metal aluminum to make aqueous aluminum acetate and gaseous hydrogen. </li></ul><ul><ul><li>Acids are always aqueous. </li></ul></ul><ul><ul><li>Metals are solid except for mercury. </li></ul></ul><ul><li>Al( s ) + HC 2 H 3 O 2 ( aq )  Al(C 2 H 3 O 2 ) 3 ( aq ) + H 2 ( g ) </li></ul><ul><li>2 Al( s ) + 6 HC 2 H 3 O 2 ( aq )  2 Al(C 2 H 3 O 2 ) 3 ( aq ) + 3 H 2 ( g ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  21. 21. Practice #3 <ul><li>Combustion of ethyl alcohol (C 2 H 5 OH) in flambé (a brandied flaming dessert). </li></ul><ul><ul><li>Combustion is burning, and therefore, reacts with O 2 . </li></ul></ul><ul><ul><li>Combustion of compounds containing C and H always make CO 2 ( g ) and H 2 O( g ) as products. </li></ul></ul><ul><li>C 2 H 5 OH( l ) + O 2 ( g )  CO 2 ( g ) + H 2 O( g ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  22. 22. Practice #3, Continued <ul><li>Combustion of ethyl alcohol (C 2 H 5 OH) in flambé (a brandied flaming dessert). </li></ul><ul><ul><li>Combustion is burning, and therefore, reacts with O 2 . </li></ul></ul><ul><ul><li>Combustion of compounds containing C and H always make CO 2 ( g ) and H 2 O( g ) as products. </li></ul></ul><ul><li>C 2 H 5 OH( l ) + O 2 ( g )  CO 2 ( g ) + H 2 O( g ) </li></ul><ul><li>C 2 H 5 OH( l ) + 3 O 2 ( g )  2 CO 2 ( g ) + 3 H 2 O( g ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  23. 23. Practice #4 <ul><li>Combustion of liquid butane (C 4 H 10 ) in a lighter. </li></ul><ul><li>C 4 H 10 ( l ) + O 2 ( g )  CO 2 ( g ) + H 2 O( g ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  24. 24. Practice #4, Continued <ul><li>Combustion of liquid butane (C 4 H 10 ) in a lighter. </li></ul><ul><li>C 4 H 10 ( l ) + O 2 ( g )  CO 2 ( g ) + H 2 O( g ) </li></ul><ul><li>2 C 4 H 10 ( l ) + 13 O 2 ( g )  8 CO 2 ( g ) + 10 H 2 O( g ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  25. 25. Aqueous Solutions <ul><li>Many times, the chemicals we are reacting together are dissolved in water. </li></ul><ul><ul><li>Mixtures of a chemical dissolved in water are called aqueous solutions . </li></ul></ul><ul><li>Dissolving the chemicals in water helps them to react together faster. </li></ul><ul><ul><li>The water separates the chemicals into individual molecules or ions. </li></ul></ul><ul><ul><li>The separate, free-floating particles come in contact more frequently so the reaction speeds up. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  26. 26. Predicting Whether a Reaction Will Occur in Aqueous Solution <ul><li>“ Forces” that drive a reaction: </li></ul><ul><ul><li>Formation of a solid. </li></ul></ul><ul><ul><li>Formation of water. </li></ul></ul><ul><ul><li>Formation of a gas. </li></ul></ul><ul><ul><li>Transfer of electrons. </li></ul></ul><ul><li>When chemicals (dissolved in water) are mixed and one of the above-noted forces occur, the reaction will generally happen. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  27. 27. Dissociation <ul><li>When ionic compounds dissolve in water, the anions and cations are separated from each other. This is called dissociation . </li></ul><ul><ul><li>However, not all ionic compounds are soluble in water! </li></ul></ul><ul><li>When compounds containing polyatomic ions dissociate , the polyatomic group stays together as one ion. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  28. 28. Electrolytes <ul><li>Electrolytes are substances whose water solution is a conductor of electricity. </li></ul><ul><li>All electrolytes have ions dissolved in water. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  29. 29. Electrolytes, Continued <ul><li>In strong electrolytes, all the electrolyte molecules or formula units are separated into ions. </li></ul><ul><li>In non electrolytes, none of the molecules are separated into ions. </li></ul><ul><li>In weak electrolytes, a small percentage of the molecules are separated into ions. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  30. 30. Types of Electrolytes <ul><li>Salts = Water soluble ionic compounds. </li></ul><ul><ul><li>All strong electrolytes. </li></ul></ul><ul><li>Acids = Form H +1 ions and anions in water solution. </li></ul><ul><ul><li>In binary acids, the anion is monoatomic. In oxyacids, the anion is polyatomic. </li></ul></ul><ul><ul><li>Sour taste. </li></ul></ul><ul><ul><li>React and dissolve many metals. </li></ul></ul><ul><ul><li>Strong acid = strong electrolyte, weak acid = weak electrolyte. </li></ul></ul><ul><li>Bases = Water-soluble metal hydroxides. </li></ul><ul><ul><li>Bitter taste, slippery (soapy) feeling solutions. </li></ul></ul><ul><ul><li>Increases the OH -1 concentration. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  31. 31. When Will a Salt Dissolve? <ul><li>A compound is soluble in a liquid if it dissolves in that liquid. </li></ul><ul><ul><li>NaCl is soluble in water, but AgCl is not. </li></ul></ul><ul><li>A compound is insoluble if a significant amount does not dissolve in that liquid. </li></ul><ul><ul><li>AgCl is insoluble in water. </li></ul></ul><ul><ul><ul><li>Though there is a very small amount dissolved, but not enough to be significant. </li></ul></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  32. 32. When Will a Salt Dissolve?, Continued <ul><li>Predicting whether a compound will dissolve in water is not easy. </li></ul><ul><li>The best way to do it is to do some experiments to test whether a compound will dissolve in water, then develop some rules based on those experimental results. </li></ul><ul><ul><li>We call this method the empirical method . </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  33. 33. Solubility Rules: Compounds that Are Generally Soluble in Water Tro's &quot;Introductory Chemistry&quot;, Chapter 7 Compounds containing the following ions are generally soluble Exceptions (when combined with ions on the left the compound is insoluble) Li + , Na + , K + , NH 4 + none NO 3 – , C 2 H 3 O 2 – none Cl – , Br – , I – Ag + , Hg 2 2+ , Pb 2+ SO 4 2– Ca 2+ , Sr 2+ , Ba 2+ , Pb 2+
  34. 34. Solubility Rules: Compounds that Are Generally Insoluble Tro's &quot;Introductory Chemistry&quot;, Chapter 7 Compounds containing the following ions are generally insoluble Exceptions (when combined with ions on the left the compound is soluble or slightly soluble ) OH – Li + , Na + , K + , NH 4 + , Ca 2+ , Sr 2+ , Ba 2+ S 2– Li + , Na + , K + , NH 4 + , Ca 2+ , Sr 2+ , Ba 2+ CO 3 2– , PO 4 3– Li + , Na + , K + , NH 4 +
  35. 35. <ul><li>Write the formulas of the products. </li></ul><ul><ul><li>Cross charges and reduce. </li></ul></ul><ul><ul><li>Na 2 CO 3 ( aq ) + CuCl 2 ( aq )  NaCl + CuCO 3 </li></ul></ul><ul><li>Balance the equation. </li></ul><ul><ul><li>Na 2 CO 3 ( aq ) + CuCl 2 ( aq )  NaCl + CuCO 3 </li></ul></ul>Example 7.7—When an Aqueous Solution of Sodium Carbonate Is Added to an Aqueous Solution of Copper(II) Chloride, a White Solid Forms, Continued. Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  36. 36. Practice – Predict the Products and Balance the Equation <ul><li>KCl( aq ) + AgNO 3 ( aq )  </li></ul><ul><li>Na 2 S( aq ) + CaCl 2 ( aq )  </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  37. 37. <ul><li>KCl( aq ) + AgNO 3 ( aq )  </li></ul><ul><li>KCl( aq ) + AgNO 3 ( aq )  KNO 3 ( aq ) + AgCl( s ) </li></ul><ul><li>Na 2 S( aq ) + CaCl 2 ( aq )  </li></ul><ul><li>Na 2 S( aq ) + CaCl 2 ( aq )  2 NaCl( aq ) + CaS( aq ) </li></ul><ul><li>No reaction. </li></ul>Practice – Predict the Products and Balance the Equation, Continued Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  38. 38. Practice—Write an Equation for the Reaction that Takes Place when an Aqueous Solution of (NH 4 ) 2 SO 4 is Mixed with an Aqueous Solution of Pb(C 2 H 3 O 2 ) 2 . Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  39. 39. Practice—Write an Equation for the Reaction that Takes Place when an Aqueous Solution of (NH 4 ) 2 SO 4 is Mixed with an Aqueous Solution of Pb(C 2 H 3 O 2 ) 2 , Continued. Tro's &quot;Introductory Chemistry&quot;, Chapter 7 (NH 4 ) 2 SO 4 ( aq ) + Pb(C 2 H 3 O 2 ) 2 ( aq )  2 NH 4 C 2 H 3 O 2 ( aq ) + PbSO 4 ( s )
  40. 40. Ionic Equations <ul><li>Equations that describe the chemicals put into the water and the product molecules are called molecular equations . </li></ul><ul><li>2 KOH( aq ) + Mg(NO 3 ) 2 ( aq )  2 KNO 3 ( aq ) + Mg(OH) 2 ( s ) </li></ul><ul><li>Equations that describe the actual dissolved species are called complete ionic equations . </li></ul><ul><ul><li>Aqueous electrolytes are written as ions. </li></ul></ul><ul><ul><ul><li>Soluble salts, strong acids, strong bases. </li></ul></ul></ul><ul><ul><li>Insoluble substances and nonelectrolytes written in molecule form. </li></ul></ul><ul><ul><ul><li>Solids, liquids, and gases are not dissolved, therefore, molecule form. </li></ul></ul></ul><ul><li>2K +1 ( aq ) + 2OH -1 ( aq ) + Mg +2 ( aq ) + 2NO 3 -1 ( aq )  K +1 ( aq ) + 2NO 3 -1 ( aq ) + Mg(OH) 2( s ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  41. 41. Writing Complete Ionic Equations <ul><li>Rewrite the molecular equation, but dissociate strong electrolytes into individual ions. </li></ul><ul><ul><li>Strong electrolytes must be aqueous. </li></ul></ul><ul><ul><ul><li>Solids, liquids, or gases cannot be electrolytes. </li></ul></ul></ul><ul><ul><li>All soluble ionic compounds are strong electrolytes. </li></ul></ul><ul><ul><li>Strong acids are strong electrolytes. </li></ul></ul><ul><ul><ul><li>HCl, HNO 3 , H 2 SO 4 . . </li></ul></ul></ul><ul><ul><ul><li>Weak acids are not written in the dissociated ion form. </li></ul></ul></ul><ul><ul><li>Molecular compounds do not have ions, leave in the molecular form. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  42. 42. Ionic Equations <ul><li>Ions that are both reactants and products are called spectator ions. </li></ul><ul><li>2K +1 ( aq ) + 2OH -1 ( aq ) + Mg +2 ( aq ) + 2NO 3 -1 ( aq )  K +1 ( aq ) + 2NO 3 -1 ( aq ) + Mg(OH) 2( s ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7 <ul><li>An ionic equation in which the spectator ions are </li></ul><ul><li>removed is called a net ionic equation. </li></ul><ul><li>2OH -1 ( aq ) + Mg +2 ( aq )  Mg(OH) 2( s ) </li></ul>
  43. 43. Writing Net Ionic Equations <ul><li>First, identify the spectator ions in the complete ionic equation. </li></ul><ul><ul><li>Identical ions on both sides of the equation. </li></ul></ul><ul><li>Cancel out the spectator ions—the result is the net ionic equation. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  44. 44. Summary <ul><li>A molecular equation is a chemical equation showing the complete, neutral formulas for every compound in a reaction. </li></ul><ul><li>A complete ionic equation is a chemical equation showing all of the species as they are actually present in solution. </li></ul><ul><li>A net ionic equation is an equation showing only the species that actually participate in the reaction. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  45. 45. Practice – Write the Ionic and Net Ionic Equation. <ul><li>K 2 SO 4 ( aq ) + Ba(NO 3 ) 2 ( aq )  2 KNO 3 ( aq ) + BaSO 4 ( s ) </li></ul><ul><li>Na 2 CO 3 ( aq ) + 2 HCl( aq )  2 NaCl( aq ) + CO 2 ( g ) + H 2 O( l ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  46. 46. Practice – Write the Ionic and Net Ionic Equation. <ul><li>K 2 SO 4 ( aq ) + Ba(NO 3 ) 2 ( aq )  2 KNO 3 ( aq ) + BaSO 4 ( s ) </li></ul><ul><li>2K + ( aq ) + SO 4 2 − ( aq ) + Ba 2+ ( aq ) + 2NO 3 − ( aq )  2K + ( aq ) + 2NO 3 − ( aq ) + BaSO 4 ( s ) </li></ul><ul><li>Ba 2+ ( aq ) + SO 4 -2 ( aq )  BaSO 4 ( s ) </li></ul><ul><li>Na 2 CO 3 ( aq ) + 2 HCl( aq )  2 NaCl( aq ) + CO 2 ( g ) + H 2 O( l ) </li></ul><ul><li>2Na + ( aq ) + CO 3 2 − ( aq ) + 2H + ( aq ) + 2 Cl − ( aq )  2Na + ( aq ) + 2Cl − ( aq ) + CO 2 ( g ) + H 2 O( l ) </li></ul><ul><li>CO 3 -2 ( aq ) + 2 H +1 ( aq )  CO 2 ( g ) + H 2 O( l ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  47. 47. Properties of Acids <ul><li>Sour taste. </li></ul><ul><li>Change color of vegetable dyes. </li></ul><ul><li>React with “active” metals, not noble metals. </li></ul><ul><ul><li>I.e., Al, Zn, Fe, but not Cu, Ag or Au. </li></ul></ul><ul><ul><li>Zn + 2 HCl  ZnCl 2 + H 2 </li></ul></ul><ul><ul><li>Corrosive. </li></ul></ul><ul><li>React with carbonates, producing CO 2 . </li></ul><ul><ul><li>Marble, baking soda, chalk, limestone. </li></ul></ul><ul><ul><li>CaCO 3 + 2 HCl  CaCl 2 + CO 2 + H 2 O </li></ul></ul><ul><li>React with bases to form ionic salts. </li></ul><ul><ul><li>And often water. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  48. 48. Common Acids Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  49. 49. Properties of Bases <ul><li>A.k.a. alkalis. </li></ul><ul><li>Taste bitter. </li></ul><ul><li>Feel slippery. </li></ul><ul><li>Change color of vegetable dyes. </li></ul><ul><ul><li>Different color than acid. </li></ul></ul><ul><ul><li>Litmus = blue. </li></ul></ul><ul><li>React with acids to form ionic salts. </li></ul><ul><ul><li>And often water. </li></ul></ul><ul><ul><li>Neutralization. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  50. 50. Common Bases Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  51. 51. Acid – Base Reactions <ul><li>Also called neutralization reactions because the acid and base neutralize each other’s properties. </li></ul><ul><li>In the reaction of an acid with a base, the H +1 from the acid combines with the OH -1 from the base to make water. </li></ul><ul><li>The cation from the base combines with the anion from the acid to make the salt. </li></ul><ul><li>acid + base  salt + water </li></ul><ul><li>2 HNO 3 ( aq ) + Ca(OH) 2 ( aq )  Ca(NO 3 ) 2 ( aq ) + 2 H 2 O( l ) </li></ul><ul><li>The net ionic equation for an acid-base reaction often is: </li></ul><ul><li>H +1 ( aq ) + OH -1 ( aq )  H 2 O( l ) </li></ul><ul><ul><li>As long as the salt that forms is soluble in water. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  52. 52. Process for Predicting the Products of an Acid – Base Reaction <ul><li>Determine what ions each aqueous reactant has. </li></ul><ul><li>Exchange ions. </li></ul><ul><ul><li>(+) ion from one reactant with (-) ion from the other. </li></ul></ul><ul><ul><li>H + combines with OH − to make water. </li></ul></ul><ul><li>Balance charges of combined ions to get formula of the salt. </li></ul><ul><li>Balance the equation. </li></ul><ul><ul><li>Count atoms. </li></ul></ul><ul><li>Determine solubility of the salt. </li></ul><ul><ul><li>Use the solubility rules. </li></ul></ul><ul><ul><li>If the salt is insoluble or slightly soluble, it will precipitate. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  53. 53. Example 7.11—Write the Molecular, Ionic, and Net-Ionic Equation for the Reaction of Aqueous Nitric Acid with Aqueous Calcium Hydroxide. <ul><li>Write the formulas of the reactants. </li></ul><ul><ul><li>HNO 3 ( aq ) + Ca(OH) 2 ( aq )  </li></ul></ul><ul><ul><li>a. Determine the ions present when each reactant dissociates. </li></ul></ul><ul><ul><li>(H + + NO 3 − ) + (Ca 2+ + OH − )  </li></ul></ul><ul><li>Exchange the ions, H +1 combines with OH − to make H 2 O( l ). </li></ul><ul><li>(H + + NO 3 − ) + (Ca 2+ + OH − )  (Ca +2 + NO 3 − ) + H 2 O( l ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  54. 54. <ul><li>Write the formula of the salt product. </li></ul><ul><ul><li>Cross charges and reduce. </li></ul></ul><ul><ul><li>HNO 3 ( aq ) + Ca(OH) 2 ( aq )  Ca(NO 3 ) 2 + H 2 O( l ) </li></ul></ul><ul><li>Balance the equation. </li></ul><ul><ul><li>May be quickly balanced by matching the numbers of H and OH to make H 2 O. </li></ul></ul><ul><ul><li>Coefficient of the salt is always 1. </li></ul></ul><ul><ul><li>2 HNO 3 ( aq ) + Ca(OH) 2 ( aq )  Ca(NO 3 ) 2 + 2 H 2 O( l ) </li></ul></ul>Example 7.11—Write the Molecular, Ionic, and Net-Ionic Equation for the Reaction of Aqueous Nitric Acid with Aqueous Calcium Hydroxide, Continued. Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  55. 55. <ul><li>Determine the solubility of the salt. </li></ul><ul><ul><li>Ca(NO 3 ) 2 is soluble. </li></ul></ul><ul><ul><li>a. Write an ( s ) after an insoluble salt and an ( aq ) after a soluble salt. </li></ul></ul><ul><li>2 HNO 3 ( aq ) + Ca(OH) 2 ( aq )  Ca(NO 3 ) 2 ( aq ) + 2 H 2 O( l ) </li></ul>Example 7.11—Write the Molecular, Ionic, and Net-Ionic Equation for the Reaction of Aqueous Nitric Acid with Aqueous Calcium Hydroxide, Continued. Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  56. 56. Example 7.11—Write the Molecular, Ionic, and Net-Ionic Equation for the Reaction of Aqueous Nitric Acid with Aqueous Calcium Hydroxide, Continued. <ul><li>Dissociate all strong electrolytes to get complete ionic equation. </li></ul><ul><ul><li>HNO 3 is a strong acid, Ca(OH) 2 and Ca(NO 3 ) 2 are ionic. </li></ul></ul><ul><ul><li>Not H 2 O. </li></ul></ul><ul><li>2H + ( aq ) + 2NO 3 − ( aq ) + Ca 2+ ( aq ) + 2OH − ( aq )  Ca 2+ ( aq ) + 2NO 3 − ( aq ) + H 2 O( l ) </li></ul><ul><li>Eliminate spectator ions to get net-ionic equation. </li></ul><ul><ul><li>2 H + ( aq ) + 2 OH − ( aq )  H 2 O( l ) </li></ul></ul><ul><ul><li>H + ( aq ) + OH − ( aq )  H 2 O( l ) </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  57. 57. Practice—Complete and Balance These Acid – Base Reactions. <ul><li>NH 4 OH( aq ) + H 2 SO 4 ( aq )  </li></ul><ul><li>Al(OH) 3 ( aq ) + H 2 SO 3 ( aq )  </li></ul><ul><li>Ba(OH) 2 ( aq ) + H 2 SO 4 ( aq )  </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  58. 58. Practice—Complete and Balance These Acid – Base Reactions, Continued. <ul><li>2 NH 4 OH( aq ) + H 2 SO 4 ( aq )  (NH 4 ) 2 SO 4 ( aq ) + 2 H 2 O( l ) </li></ul><ul><li>2 Al(OH) 3 ( aq ) + 3 H 2 SO 3 ( aq )  Al 2 (SO 3 ) 3 ( s ) + 6 H 2 O( l ) </li></ul><ul><li>Ba(OH) 2 ( aq ) + H 2 SO 4 ( aq )  BaSO 4 ( s ) + 2 H 2 O( l ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  59. 59. Gas Evolution Reactions <ul><li>Reactions in which the driving force is the production of a material that escapes as a gas are called gas evolution reactions . </li></ul><ul><li>Some reactions form a gas directly from the ion exchange. </li></ul><ul><li>K 2 S( aq ) + H 2 SO 4 ( aq )  K 2 SO 4 ( aq ) + H 2 S( g ) </li></ul><ul><li>Other reactions form a gas by the decomposition of one of the ion exchange products into a gas and water. </li></ul><ul><li>K 2 SO 3 ( aq ) + H 2 SO 4 ( aq )  K 2 SO 4 ( aq ) + H 2 SO 3 ( aq ) </li></ul><ul><li>H 2 SO 3  H 2 O( l ) + SO 2 ( g ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  60. 60. Compounds that Undergo Gas Evolving Reactions Tro's &quot;Introductory Chemistry&quot;, Chapter 7 Reactant type Reacting with Ion exchange product Decom-pose? Gas formed Example Metal n S, metal HS Acid H 2 S No H 2 S K 2 S( aq ) + 2HCl( aq )  2KCl( aq ) + H 2 S( g ) Metal n CO 3 , metal HCO 3 Acid H 2 CO 3 Yes CO 2 K 2 CO 3 ( aq ) + 2HCl( aq )  2KCl( aq ) + CO 2 ( g ) + H 2 O( l ) Metal n SO 3 metal HSO 3 Acid H 2 SO 3 Yes SO 2 K 2 SO 3 ( aq ) + 2HCl( aq )  2KCl( aq ) + SO 2 ( g ) + H 2 O( l ) (NH 4 ) n anion Base NH 4 OH Yes NH 3 KOH( aq ) + NH 4 Cl( aq )  KCl( aq ) + NH 3 ( g ) + H 2 O( l )
  61. 61. Process for Predicting the Products of a Gas-Evolving Reaction <ul><li>Determine what ions each aqueous reactant has. </li></ul><ul><li>Exchange ions. </li></ul><ul><ul><li>(+) ion from one reactant with (-) ion from the other. </li></ul></ul><ul><li>Balance charges of combined ions to get formula of each product. </li></ul><ul><li>Check to see if either product is H 2 S. </li></ul><ul><li>Check to see if either product decomposes. If so, rewrite as H 2 O( l ) and a gas. </li></ul><ul><ul><li>See Table 7.4 </li></ul></ul><ul><li>Balance the equation. </li></ul><ul><li>Determine solubility of other product in water. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  62. 62. Example—When an Aqueous Solution of Sodium Sulfite Is Added to an Aqueous Solution of Nitric Acid, a Gas Evolves. <ul><li>Write the formulas of the reactants. </li></ul><ul><ul><li>Na 2 SO 3 ( aq ) + HNO 3 ( aq )  </li></ul></ul><ul><ul><li>a. Determine the ions present when each reactant dissociates. </li></ul></ul><ul><ul><li>(Na +1 + SO 3 -2 ) + (H +1 + NO 3 -1 )  </li></ul></ul><ul><li>Exchange the ions. </li></ul><ul><li>(Na +1 + SO 3 -2 ) + (H +1 + NO 3 -1 )  (Na +1 + NO 3 -1 ) + (H +1 + SO 3 -2 ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  63. 63. <ul><li>Write the formulas of the products. </li></ul><ul><ul><li>Cross charges and reduce. </li></ul></ul><ul><li>Na 2 SO 3 ( aq ) + HNO 3 ( aq )  NaNO 3 + H 2 SO 3 </li></ul><ul><li>Check to see if either product is H 2 S. No. </li></ul><ul><li>Check to see of either product decomposes. Yes. </li></ul><ul><ul><li>H 2 SO 3 decomposes into SO 2 ( g ) + H 2 O( l ). </li></ul></ul><ul><li>Na 2 SO 3 ( aq ) + HNO 3 ( aq )  NaNO 3 + SO 2 ( g ) + H 2 O( l ) </li></ul>Example—When an Aqueous Solution of Sodium Sulfite Is Added to an Aqueous Solution of Nitric Acid, a Gas Evolves, Continued. Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  64. 64. <ul><li>Balance the equation. </li></ul><ul><li>Na 2 SO 3 ( aq ) + 2 HNO 3 ( aq )  NaNO 3 + SO 2 ( g ) + H 2 O( l ) </li></ul><ul><li>Determine the solubility of other product. </li></ul><ul><ul><li>NaNO 3 is soluble. </li></ul></ul><ul><ul><li>a. Write an ( s ) after the insoluble products and an ( aq ) after the soluble products. </li></ul></ul><ul><li>Na 2 SO 3 ( aq ) + 2 HNO 3 ( aq )  NaNO 3 ( aq ) + SO 2 ( g ) + H 2 O( l ) </li></ul>Example—When an Aqueous Solution of Sodium Sulfite Is Added to an Aqueous Solution of Nitric Acid, a Gas Evolves, Continued. Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  65. 65. Practice—Complete the Following Reactions. <ul><li>PbS( s ) + H 2 SO 4 ( aq )  </li></ul><ul><li>HNO 3 ( aq ) + NaHCO 3 ( aq )  </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  66. 66. Practice—Complete the Following Reactions, Continued. <ul><li>PbS( s ) + H 2 SO 4 ( aq )  PbSO 4 ( s ) + H 2 S( g ) </li></ul><ul><li>HNO 3 ( aq ) + NaHCO 3 ( aq )  NaNO 3 ( aq ) + CO 2 ( g ) + H 2 O( l ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  67. 67. Other Patterns in Reactions <ul><li>The precipitation, acid – base, and gas evolving reactions all involved exchanging the ions in the solution. </li></ul><ul><li>Other kinds of reactions involve transferring electrons from one atom to another. These are called oxidation – reduction reactions . </li></ul><ul><ul><li>Also known as redox reactions. </li></ul></ul><ul><ul><li>Reactions of materials with O 2 are redox reactions. </li></ul></ul><ul><ul><li>Unlike the others, many of these reactions are not done by dissolving the reactants in water. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  68. 68. Oxidation – Reduction Reactions <ul><li>We say that the element that loses electrons in the reaction is oxidized . </li></ul><ul><li>And the substance that gains electrons in the reaction is reduced . </li></ul><ul><li>You cannot have one without the other. </li></ul><ul><li>In combustion, the O atoms in O 2 are reduced, and the non-O atoms in the other material are oxidized. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  69. 69. Combustion as Redox <ul><li>In the following reaction: </li></ul><ul><li>2 Mg( s ) + O 2 ( g )  2 MgO( s ) </li></ul><ul><li>The magnesium atoms are oxidized. </li></ul><ul><li>Mg 0  Mg 2+ + 2 e  </li></ul><ul><li>The oxygen atoms are reduced. </li></ul><ul><li>O 0 + 2 e   O 2  </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  70. 70. Combustion as Redox, Continued <ul><li>Even though the following reaction does not involve ion formation, electrons are still transferred. </li></ul><ul><li>CH 4 ( g ) + 2 O 2 ( g )  CO 2 ( g ) + 2 H 2 O( g ) </li></ul><ul><li>The carbon atoms are oxidized. </li></ul><ul><li>C  4  C +4 + 8 e  </li></ul><ul><ul><li>These are not charges, they are called oxidation numbers , but they help us see the electron transfer. </li></ul></ul><ul><li>The oxygen atoms are reduced. </li></ul><ul><li>O 0 + 2 e   O  2 </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  71. 71. Summary <ul><li>Redox reactions occur when: </li></ul><ul><ul><li>A substance reacts with O 2 . </li></ul></ul><ul><ul><li>A metal combines with a nonmetal. </li></ul></ul><ul><ul><li>In general, whenever electrons are transferred. </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  72. 72. Reactions of Metals with Nonmetals (Oxidation – Reduction) <ul><li>Metals react with nonmetals to form ionic compounds. </li></ul><ul><ul><li>Ionic compounds are solids at room temperature. </li></ul></ul><ul><li>The metal loses electrons and becomes a cation. </li></ul><ul><ul><li>The metal undergoes oxidation . </li></ul></ul><ul><li>The nonmetal gains electrons and becomes an anion. </li></ul><ul><ul><li>The nonmetal undergoes reduction . </li></ul></ul><ul><li>In the reaction, electrons are transferred from the metal to the nonmetal. </li></ul><ul><li>2 Na( s ) + Cl 2 ( g )  NaCl( s ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  73. 73. Ionic Compound Formation as Redox <ul><li>In the reaction: </li></ul><ul><li>Mg( s ) + Cl 2 ( g )  MgCl 2 ( s ) </li></ul><ul><li>The magnesium atoms are oxidized. </li></ul><ul><li>Mg 0  Mg 2+ + 2 e  </li></ul><ul><li>The chlorine atoms are reduced. </li></ul><ul><li>Cl 0 + 1 e   Cl  </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  74. 74. Recognizing Redox Reactions <ul><li>Any reaction where O 2 is a reactant or a product is a redox reaction. </li></ul><ul><li>Any reaction between a metal and a nonmetal is redox. </li></ul><ul><li>Any reaction where electrons are transferred is redox. </li></ul><ul><ul><li>When a free element gets combined into a compound, it will be either oxidized or reduced. </li></ul></ul><ul><ul><li>N 2 ( g ) + H 2 ( g )  NH 3 ( g ) </li></ul></ul><ul><ul><li>When a metal cation changes its charge, it will be either oxidized if its charge increases or reduced if its charge decreases. </li></ul></ul><ul><ul><li>CuCl( aq ) + FeCl 3 ( aq )  FeCl 2 ( aq ) + CuCl 2 ( aq ) </li></ul></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  75. 75. Practice—Decide Whether Each of the Following Reactions Is a Redox Reaction. <ul><li>2 Al( s ) + 3 Br 2 ( l )  2 AlBr 3 ( s ) </li></ul><ul><li>CaSO 3 ( s ) + 2 HCl( aq )  CaCl 2 ( aq ) + SO 2 ( g ) + H 2 O( l ) </li></ul><ul><li>Fe 2 O 3 ( s ) + C( s )  2 Fe( s ) + 3 CO( g ) </li></ul><ul><li>SO 2 ( g ) + O 2 ( g ) + H 2 O( l )  H 2 SO 4 ( aq ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  76. 76. Practice—Decide Whether Each of the Following Reactions Is a Redox Reaction, Continued. <ul><li>2 Al( s ) + 3 Br 2 ( l )  2 AlBr 3 ( s )— Yes, metal + nonmetal . </li></ul><ul><li>CaSO 3 ( s ) + 2 HCl( aq )  CaCl 2 ( aq ) + SO 2 ( g ) + H 2 O( l )— No, this is a gas evolving reaction. </li></ul><ul><li>Fe 2 O 3 (s) + C(s)  2 Fe(s) + 3 CO(g)— Yes, the Fe is reduced and the C gets combined. </li></ul><ul><li>SO 2 ( g ) + O 2 ( g ) + H 2 O( l )  H 2 SO 4 ( aq )— Yes, O 2 reactant. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  77. 77. Combustion Reactions <ul><li>Reactions in which O 2 ( g ) is a reactant are called combustion reactions . </li></ul><ul><li>Combustion reactions release lots of energy. They are exothermic. </li></ul><ul><li>Combustion reactions are a subclass of oxidation – reduction reactions. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7 2 C 8 H 18 ( g ) + 25 O 2 ( g )  16 CO 2 ( g ) + 18 H 2 O( g )
  78. 78. Products of Combustion <ul><li>When a material burns that contains carbon and hydrogen, the products are always CO 2 ( g ) and H 2 O( g ). </li></ul><ul><li>The reaction for the combustion of ethylene, C 2 H 4 ( g ) is: </li></ul><ul><li>C 2 H 4 ( g ) + 3 O 2 ( g )  2 CO 2 ( g ) + 2 H 2 O( g ) </li></ul><ul><li>The reaction for the combustion of ethylene glycol, C 2 H 6 O 2 ( g ) is: </li></ul><ul><li>2 C 2 H 6 O 2 ( g ) + 5 O 2 ( g )  4 CO 2 ( g ) + 6 H 2 O( g ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  79. 79. Combustion Products <ul><li>To predict the products of a combustion reaction, combine each element in the other reactant with oxygen. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7 Reactant Combustion product Contains C CO 2 (g) Contains H H 2 O(g) Contains S SO 2 (g) Contains N NO(g) or NO 2 (g) Contains metal M 2 O n (s)
  80. 80. Practice—Write the Equation for Each Reaction. <ul><li>Combustion of the anesthetic cyclopropane, C 3 H 6 . </li></ul><ul><li>Combustion of the non-toxic antifreeze propylene glycol, C 3 H 8 O 2 . </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  81. 81. Practice—Write the Equation for Each Reaction, Continued. <ul><li>Combustion of the anesthetic cyclopropane, C 3 H 6 ( g ). </li></ul><ul><li>2 C 3 H 6 ( g ) + 9 O 2 ( g )  6 CO 2 ( g ) + 6 H 2 O( g ) </li></ul><ul><li>Combustion of the non-toxic antifreeze propylene glycol, C 3 H 8 O 2 ( l ). </li></ul><ul><li>2 C 3 H 6 O 2 ( l ) + 7 O 2 ( g )  6 CO 2 ( g ) + 6 H 2 O( g ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  82. 82. Classifying Reactions <ul><li>One way is based on the process that happens. </li></ul><ul><ul><li>Precipitation, neutralization, formation of a gas, or transfer of electrons. </li></ul></ul>
  83. 83. Classifying Reactions, Continued <ul><li>Another scheme classifies reactions by what the atoms do. </li></ul>Type of reaction General equation Synthesis A + B  AB Decomposition AB  A + B Displacement A + BC  AC + B Double displacement AB + CD  AD + CB
  84. 84. Synthesis Reactions <ul><li>Also known as composition or combination reactions. </li></ul><ul><li>Two (or more) reactants combine together to make one product . </li></ul><ul><ul><li>Simpler substances combining together. </li></ul></ul><ul><li>2 CO + O 2  2 CO 2 </li></ul><ul><li>2 Mg + O 2  2 MgO </li></ul><ul><li>HgI 2 + 2 KI  K 2 HgI 4 </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  85. 85. Decomposition Reactions <ul><li>A large molecule is broken apart into smaller molecules or its elements. </li></ul><ul><ul><li>Caused by addition of energy into the molecule. </li></ul></ul><ul><li>Have only one reactant , make 2 or more products. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  86. 86. Decomposition of Water Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  87. 87. Single Displacement Reactions <ul><li>Reactions that involve one atom displacing another and replacing it in a compound. </li></ul><ul><li>In the reaction Zn( s ) + 2 HCl( aq )  ZnCl 2 ( aq ) + H 2 ( g ), the atom Zn displaces H from the compound. </li></ul><ul><li>Other examples of displacement reactions are: </li></ul><ul><li>Fe 2 O 3 ( s ) + Al( s )  Fe( s ) + Al 2 O 3 ( s ) </li></ul><ul><li>2 Na( s ) + 2 H 2 O( aq )  2 NaOH( aq ) + H 2 ( g ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  88. 88. Displacement of Copper by Zinc Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  89. 89. Double Displacement Reactions <ul><li>Two ionic compounds exchange ions. </li></ul><ul><li>May be followed by decomposition of one of the products to make a gas. </li></ul><ul><li>X  Y  ( aq ) + A  B  ( aq )  XB + AY </li></ul><ul><li>Precipitation, acid – base, and gas evolving reactions are also double displacement reactions. </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  90. 90. Examples of Double Displacement <ul><li>CaCl 2 ( aq ) + Na 2 CO 3 ( aq )  CaCO 3 ( s ) + 2 NaCl( aq ) </li></ul><ul><li>Ba(OH) 2 ( s ) + 2 HNO 3 ( aq )  Ba(NO 3 ) 2 ( aq ) + 2 H 2 O( l ) </li></ul><ul><li>Li 2 CO 3 ( aq ) + 2 HCl( aq )  2 LiCl( aq ) + CO 2 ( g ) + H 2 O( l ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  91. 91. Practice—Classify the Following Reactions as Synthesis, Decomposition, Single Displacement, or Double Displacement. <ul><li>3 Mg( s ) + 2 FeCl 3 ( aq )  3 MgCl 2 ( aq ) + 2 Fe( s ) </li></ul><ul><li>CO 2 ( g ) + H 2 O( l )  H 2 CO 3 ( aq ) </li></ul><ul><li>3 KOH( aq ) + H 3 PO 4 ( aq )  K 3 PO 4 ( aq ) + 3 H 2 O( l ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7
  92. 92. Practice—Classify the Following Reactions as Synthesis, Decomposition, Single Displacement, or Double Displacement, Continued. <ul><li>3 Mg( s ) + 2 FeCl 3 ( aq )  3 MgCl 2 ( aq ) + 2 Fe( s ) </li></ul><ul><li>CO 2 ( g ) + H 2 O( l )  H 2 CO 3 ( aq ) </li></ul><ul><li>3 KOH( aq ) + H 3 PO 4 ( aq )  K 3 PO 4 ( aq ) + 3 H 2 O( l ) </li></ul>Tro's &quot;Introductory Chemistry&quot;, Chapter 7 Single displacement. Double displacement. Decomposition. Synthesis.

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