Types of Chemical Reactions

1. Types of Chemical Reactions Writing Chemical Reactions

2. Types of Reactions • Many chemical reactions have defining characteristics which allow them to be classified as to type.

3. Types of Chemical Reactions • The five types of chemical reactions in this unit are: • Combination (Synthesis) • Decomposition • Single Replacement • Double Replacement • Combustion

4. Synthesis Reactions • Two or more substances combine to form a more complex substance. • The general form is A + X AX • Example: • Magnesium + oxygen  magnesium oxide • 2Mg + O2 2MgO

5. Magnesium + Oxygen

6. Synthesis Reactions • Combination reactions may also be called composition or synthesis reactions.

7. Synthesis Reactions • K + Cl2 • Write the ions: K+ Cl- • Balance the charges: KCl • Balance the equation: 2K + Cl2  2KCl

8. Decomposition Reactions • One substance reacts to form two or more substances. • The general form is AX  A + X • Example: • Water can be decomposed by electrolysis. • 2H2O  2H2 + O2

9. Electrolysis of Water

10. Decomposition Reactions • CaCO3 CaO + CO2 • H2CO3  H2O + CO2 • Ca(OH)2 CaO + H2O • 2KClO3 2KCl + 3O2 • Zn(ClO3)2  ZnCl2 + 3O2

11. Single Replacement Reactions • A metal will replace a metal ion in a compound. • The general form is A + BX  AX + B

12. Single Replacement Reactions • Examples: • Ni + AgNO3 • Nickel replaces the metallic ion Ag+. • The silver becomes free silver and the nickel becomes the nickel(II) ion. • Ni + AgNO3 Ag + Ni(NO3)2 • Balance the equation: • Ni + 2AgNO3  2Ag + Ni(NO3)

13. Single Replacement Reactions • Not all single replacement reactions that can be written actually happen. • The metal must be more active than the metal ion. • Aluminum is more active than iron in Al + Fe2O3 in the following reaction:

14. Al + Fe2O3 • Aluminum will replace iron(III) as was seen in the video. • Iron(III) becomes Fe and aluminum metal becomes Al3+. • 2Al + Fe2O3 2Fe + Al2O3

15. Double Replacement Reactions • Ions of two compounds exchange places with each other. • The general form is AX + BY  AY + BX • Metathesis is an alternate name for double replacement reactions.

16. Double Replacement • NaOH + CuSO4 • The Na+ and Cu2+ switch places. • Na+ combines with SO42- to form Na2SO4. • Cu2+ combines with OH- to form Cu(OH)2 • NaOH + CuSO4  Na2SO4 + Cu(OH)2 • 2NaOH + CuSO4  Na2SO4 + Cu(OH)2

17. Double Replacement • CuSO4 + Na2CO3 • Cu2+ combines with CO32- to form CuCO3. • Na+ combines with SO42- to form Na2SO4. • CuSO4 + Na2CO3  CuCO3 + Na2SO4

18. Combustion Reaction • When a substance combines with oxygen, a combustion reaction results. • The combustion reaction may also be an example of an earlier type such as 2Mg + O2 2MgO. • The combustion reaction may be burning of a fuel.

19. Combustion Reaction • Methane, CH4, is natural gas. • When hydrocarbon compounds are burned in oxygen, the products are water and carbon dioxide. • CH4 + O2 CO2 + H2O • CH4 + 2O2  CO2 + 2H2O

20. Combustion Reactions • Combustion reactions involve light and heat energy released. • Natural gas, propane, gasoline, etc. are burned to produce heat energy. • Most of these organic reactions produce water and carbon dioxide.

21. Practice • Classify each of the following as to type: • H2 + Cl2 2HCl • Combination • Ca + 2H2O  Ca(OH)2 + H2 • Single replacement

22. Practice • 2CO + O2 2CO2 • Combination and combustion • 2KClO3  2KCl + 3O2 • Decomposition

23. Practice • FeS + 2HCl  FeCl2 + H2S • Double replacement • Zn + HCl  ? • Single replacement • Zn + 2HCl  ZnCl2 + H2