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Types of Chemical Reactions

Types of Chemical Reactions. There are thousands of known chemical reactions. We can ’ t memorize them all. But, we can try to classify or characterize them to help us understand what is going on.

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Types of Chemical Reactions

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  1. Types of Chemical Reactions

  2. There are thousands of known chemical reactions. • We can’t memorize them all. • But, we can try to classify or characterize them to help us understand what is going on. • We will look at five basic types of chemical reactions - but this method of classification is not the only way to look at chemical reactions.

  3. The Five Types of Reactions • Composition • Decomposition • Single-Replacement • Double-Replacement • Combustion We will look at each of these types of reactions individually in more detail.

  4. composition reactions • Two or more substances combine to form a different compound. A + X → AX • A typical example is the formation of a metal oxide or sulfide. 2 Mg(s) + O2(g) → 2 MgO(s) 16 Rb(s) + S8(s) → 8 Rb2S(s)

  5. composition reactions • Two or more substances combine to form a different compound. A + X → AX • Non-metals will also react with oxygen or sulfur to form compounds. S8(s) + O2(g) → 8 SO2(g) C(s) + O2(g) → CO2(g) 2 H2(g) + O2(g) → 2 H2O(g)

  6. composition reactions • Two or more substances combine to form a different compound. A + X → AX • Metals will also react with halogens to form new compounds. 2 Na(s) + Cl2(g) → 2 NaCl(s) Sr(s) + Br2(l) → SrBr2(s)

  7. composition reactions • Two or more substances combine to form a different compound. A + X → AX • Metal oxides can also react with water to produce hydroxides. CaO(s) + H2O(l) → Ca(OH)2(s)

  8. Decomposition Reactions • In a decomposition reaction, a single compound undergoes a reaction that produces two or more simpler substances. AX → A + X • This is the opposite of the synthesis reaction. • The simplest example is the decomposition of a binary compound into its elements. 2 H2O(l) → 2 H2(g) + O2(g) This is called electrolysis.

  9. Decomposition Reactions • In a decomposition reaction, a single compound undergoes a reaction that produces two or more simpler substances. AX → A + X • This is the opposite of the synthesis reaction. • The simplest example is the decomposition of a binary compound into its elements. 2 HgO(s) → 2 Hg(l) + O2(g)

  10. Decomposition Reactions • In a decomposition reaction, a single compound undergoes a reaction that produces two or more simpler substances. AX → A + X • Metal carbonates decompose into metal oxides and carbon dioxide. CuCO3(s) → CuO(s) + CO2(g)

  11. Decomposition Reactions • In a decomposition reaction, a single compound undergoes a reaction that produces two or more simpler substances. AX → A + X • Metal hydroxides decompose into metal oxides and water. Ca(OH)2(s) → CaO(s) + H2O(g)

  12. Decomposition Reactions • In a decomposition reaction, a single compound undergoes a reaction that produces two or more simpler substances. AX → A + X • Metal chlorates decompose into metal chlorides and oxygen. 2 KClO3(s) → 2 KCl(s) + 3 O2(g)

  13. Decomposition Reactions • In a decomposition reaction, a single compound undergoes a reaction that produces two or more simpler substances. AX → A + X • Certain acids decompose into non-metal oxides and water. H2CO3(aq) → CO2(g) + H2O(l) This is what happens when a soda gives off fizz.

  14. Single-Replacement Reactions • In these reactions, one element replaces a similar element in a compound. A + BX → AX + B or Y + BX → BY + X • Typical single-replacement reactions include: • Replacement of a metal in a compound with a more active metal. 2 Al(s) + 3 Pb(NO3)2(aq) → 3 Pb(s) + 2 Al(NO3)3(aq) Aluminum is more active than lead.

  15. Single-Replacement Reactions • In these reactions, one element replaces a similar element in a compound. A + BX → AX + B or Y + BX → BY + X • Typical single-replacement reactions include: • Replacement of hydrogen in water by a metal. 2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g)

  16. Single-Replacement Reactions • In these reactions, one element replaces a similar element in a compound. A + BX → AX + B or Y + BX → BY + X • Typical single-replacement reactions include: • Replacement of hydrogen in an acid by a metal. Mg(s) + 2 HCl(aq) → H2(g) + MgCl2(aq)

  17. Single-Replacement Reactions • In these reactions, one element replaces a similar element in a compound. A + BX → AX + B or Y + BX → BY + X • Typical single-replacement reactions include: • Replacement of one halogen in a compound by another, more active halogen. Cl2(g) + 2 KBr(aq) → 2 KCl(aq) + Br2(l)

  18. Single-Replacement Reactions • In these reactions, one element replaces a similar element in a compound. A + BX → AX + B or Y + BX → BY + X • Typical single-replacement reactions include: • Replacement of one halogen in a compound by another, more active halogen. Br2(g) + KCl(aq) → no reaction Chlorine is more active than bromine.

  19. double-Replacement Reactions • In these reactions, the ions of two compounds exchange places in an aqueous solution to form two new compounds. AX + BY → AY + BX • One of the compounds formed is a precipitate, an insoluble gas, or a molecular compound (such as water).

  20. double-Replacement Reactions • In these reactions, the ions of two compounds exchange places in an aqueous solution to form two new compounds. AX + BY → AY + BX • Examples of reactions that form precipitates include: 2 KI(aq) + Pb(NO3)2(aq) → PbI2(s) + 2 KNO3(aq) yellow solid

  21. double-Replacement Reactions • In these reactions, the ions of two compounds exchange places in an aqueous solution to form two new compounds. AX + BY → AY + BX • Examples of reactions that form precipitates include: K2SO4(aq) + BaCl2(aq) → BaSO4(s) + 2 KCl(aq) white solid

  22. double-Replacement Reactions • In these reactions, the ions of two compounds exchange places in an aqueous solution to form two new compounds. AX + BY → AY + BX • An example of a reaction that forms an insoluble gas includes: FeS(s) + 2 HCl(aq) → H2S(g) + FeCl2(aq)

  23. double-Replacement Reactions • In these reactions, the ions of two compounds exchange places in an aqueous solution to form two new compounds. AX + BY → AY + BX • Acid/base reactions are examples of reactions that form water. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)

  24. Combustion Reactions • In these reactions, a substance combines with oxygen, releasing a large amount of energy in the form of light and heat and forming water. • The combustion of hydrogen produces water. 2 H2(g) + O2(g) → 2 H2O(g)

  25. Combustion Reactions • In these reactions, a substance combines with oxygen, releasing a large amount of energy in the form of light and heat and forming water. • The combustion of hydrocarbons (compounds made of hydrogen and carbon) produces water and carbon dioxide. CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l)

  26. Combustion Reactions • In these reactions, a substance combines with oxygen, releasing a large amount of energy in the form of light and heat and forming water. • The combustion of hydrocarbons (compounds made of hydrogen and carbon) produces water and carbon dioxide. 2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(l)

  27. Summary • Composition • A + X → AX • Decomposition • AX → A + X • Single-Replacement • A + BX → AX + B • AX + Y → AY + X • Double-Replacement • AX + BY → AY + BX • Combustion • A + O2 → CO2 + H2O

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