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Chemical Reactions:

Chemical Reactions:. Reactants change chemical and physical properties. …. to become new substances made from the same elements; these are called products. When you write a chemical reaction…. The word equation explains what you begin with, and what you have at the end of the reaction.

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Chemical Reactions:

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  1. Chemical Reactions: Reactants change chemical and physical properties …. to become new substances made from the same elements; these are called products.

  2. When you write a chemical reaction… • The word equation explains what you begin with, and what you have at the end of the reaction. • The reactants FORM, YIELD, or MAKE the products. • Physical states may be included: • (aq) = aqueous • (l) = liquid • (s) or (cr) = solid or crystalline • (g) = gaseous Example: solid sodium reacts with water to form aqueous sodium hydroxide and hydrogen gas.

  3. Types of Reactions • Synthesis or Composition • Decomposition • Single Replacement • Double Displacement • Combustion Reactions A + B  AB HONCl BrIF A new twist To writing Formulas. These are Always written As diatomic Molecules. AB  A + B AB + C  AC + B AB + CD  AD + CB CxHy + O2 CO2 + H2O

  4. Writing Equations: • Subscripts describe the chemical composition of the substance. These are determined by the electrons in the atoms and MAY NOT BE CHANGED when balancing equations. • Coefficients are used to balance equations. 2 2 Na + Cl2 NaCl

  5. Composition/ Synthesis Reactions • A + X  AX • An element may react with oxygen to form the oxide (oxidation) X A

  6. Composition/ Synthesis Reactions • O2 + 2Mg  2 MgO • oxygen reacts with magnesium to form magnesium oxide Mg O O Mg

  7. Composition/ Synthesis Reactions • C + O2 CO2 • carbon reacts with oxygen to form carbon dioxide O C O

  8. Practice predicting reactions with oxide and sulfides O2 • 2Fe + ____  2FeO • 4 Fe + 3 ___  2 Fe2O3 • S8 + 8 O2  8 ____ • 8 Ba + S8  8 ____ O2 SO2 BaS

  9. More Composition/ Synthesis Reactions • Fe + S  FeS • Iron reacts with sulfur to form iron (II) sulfide S2- S Fe Fe2+

  10. More Composition/ Synthesis Reactions Na • Na + S  Na2S • Sodium reacts with sulfur to form sodium sulfide S2- Na+ S Na Na+

  11. Metals react with halogens. • 2Na + Cl2 2 NaCl • 2 Co + 3 F2  2 CoF3 • 2 K + I2  2 KI • Sr + Br2  SrBr2 • 2Mg + O2 2 MgO

  12. Synthesis reactions can also occur with oxides. • Active metal oxides react with water to form hydroxides. ex: • CaO + H2O  Ca(OH)2 • Many oxides of nonmetals react with water to form oxyacids. ex: • SO2 + H2O  H2SO3 • Some metal oxides react with nonmetal oxides to form salts. • CaO + SO2  CaSO3

  13. Practice • Active metal oxides react with water to form hydroxides. ex: • MgO + H2O  ________ • Many oxides of nonmetals react with water to form oxyacids. ex: • SO3 + H2O  _________ • Some metal oxides react with nonmetal oxides to form salts. • Na2 O + 2NO2  ________ Mg(OH)2 H2SO4 2 NaNO3

  14. DecompositionAX  A + X • 2H2O  2H2 + O2 H O H H O H Electrolysis: decomposition of a substance by an electric current.

  15. DecompositionAX  A + X • 2HgO  2Hg + O2 Hg O This reaction occurs when you heat orange colored mercury (II) oxide. Silver mercury and oxygen gas form. Hg O

  16. Decompositionof metal carbonatesACO3 AO + CO2(g) • CaCO3 (s) CaO (s) + CO2(g) O Ca This reaction occurs when you heat calcium carbonate. calcium oxide and carbon dioxide form. C O O

  17. Decompositionof metal hydroxidesAOH  AO + CO2(g) • Ca(OH)2 (s) CaO (s) + H2O (g) H O Ca This reaction occurs when you heat calcium hydroxide calcium oxide and water form. O H

  18. Decomposition of metal chloratesAClO3 ACl + O2(g) • 2KClO3 (s) 2KCl (s) + 3O2(g) O O Cl Cl K K O O This reaction occurs when you heat potassium chlorate. potassium chloride and oxygen form. O O

  19. Decomposition of acidsH2CO3 (aq) H2O (g) + CO2(g) O H H C Carbonic acid decomposes when warmed. water and carbon dioxide form. O O

  20. O O O O O O N N N N N N O O O O O O O O O O O O Single DisplacementA+ BX AX + Bor:Y + BX  BY + X • Replacement of a metal in a compound by another metal. 2 Al (s) + 3Pb(NO3)2 3Pb +2 Al(NO3)3 Pb2+ Al Pb2+ Al Pb2+

  21. O O O O O O N N N N N N O O O O O O O O O O O O Single DisplacementA+ BX AX + Bor:Y + BX  BY + X • Replacement of a metal in a compound by another metal. 2 Al (s) + 3Pb(NO3)2 3Pb +2 Al(NO3)3 Pb Al3+ Al3+ Pb Pb

  22. Single DisplacementA+ BX AX + Bor:Y + BX  BY + X • Replacement of a hydrogen in a compound by a metal. 2 Na (s) + 2 H2O (l) 2 NaOH (aq) + H2(g) H O Na Na H H O H

  23. Single DisplacementA+ BX AX + Bor:Y + BX  BY + X • Replacement of a hydrogen in a compound by a metal. Mg (s) + 2 HCl (aq) MgCl2(aq) + H2(g) Cl Mg H Cl H

  24. Single DisplacementA+ BX AX + Bor:Y + BX  BY + X • Replacement of halogens Cl2(g) + 2 KBr (aq) 2 KCl (aq) + Br2(g) Br Cl K Cl Br K

  25. O O N N O O O O Double Replacement Reactions (double displacement) • Formation of a precipitate. • 2 KI (aq) + Pb(NO3)2 (aq)  PbI2 (s) + 2 KNO3 (aq) I Pb2+ I K K

  26. Double Replacement Reactions (double displacement) • Formation of a gas. • FeS (s) + 2 HCl(aq)  H2S (g) + FeCl2 (aq) S Fe2+ Cl Cl H H

  27. Double Replacement Reactions (double displacement) • Formation of a water. • NaOH (s) + HCl(aq)  H2O (l) + NaCl2 (aq) H O Na+ Cl H

  28. Combustion Reactions • A substance combines with oxygen, releasing a large amount of energy in the form of light and heat. 2 H2 (g) + O2 (g)  2 H2O O H O H H H

  29. Combustion Reactions • A substance combines with oxygen, releasing a large amount of energy in the form of light and heat. C3H8 (g) +5 O2 (g)  4 H2O + 3 CO2 O O O O H O H H H C O C C O H O H H O H O

  30. Combustion Reactions • A substance combines with oxygen, releasing a large amount of energy in the form of light and heat. C3H8 (g) +5 O2 (g)  4 H2O + 3 CO2 O O H C O O H H H O H H O C H O O C O O H

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