Types of Chemical Reactions Writing Chemical Reactions

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

Types of Chemical Reactions The five types of chemical reactions in this unit are: The five types of chemical reactions in this unit are: Combination Combination Decomposition Decomposition Single Replacement Single Replacement Double Replacement Double Replacement Combustion Combustion

Combination Reactions Two or more substances combine to form one substance. Two or more substances combine to form one substance. The general form is A + X  AX The general form is A + X  AX Example: Example: Magnesium + oxygen  magnesium oxide Magnesium + oxygen  magnesium oxide 2Mg + O 2  2MgO 2Mg + O 2  2MgO

Magnesium + Oxygen

Combination Reactions Combination reactions may also be called composition or synthesis reactions. Combination reactions may also be called composition or synthesis reactions. Some types of combination reactions: Some types of combination reactions: Combination of elements Combination of elements K + Cl 2  K + Cl 2  One product will be formed One product will be formed

Combination Reactions K + Cl 2  K + Cl 2  Write the ions: K + Cl - Write the ions: K + Cl - Balance the charges: KCl Balance the charges: KCl Balance the equation: 2K + Cl 2  2KCl Balance the equation: 2K + Cl 2  2KCl

Combination Reactions Some types of combination reactions: Some types of combination reactions: Oxide + water  Oxide + water  Nonmetal oxide + water  acid Nonmetal oxide + water  acid SO 2 + H 2 O  H 2 SO 3 SO 2 + H 2 O  H 2 SO 3 Metal oxide + water  base Metal oxide + water  base BaO + H 2 O  Ba(OH) 2 BaO + H 2 O  Ba(OH) 2

Combination Reactions Some types of combination reactions: Some types of combination reactions: Metal oxides + nonmetal oxides Metal oxides + nonmetal oxides Na 2 O + CO 2  Na 2 CO 3 Na 2 O + CO 2  Na 2 CO 3 CaO + SO 2  CaSO 3 CaO + SO 2  CaSO 3

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

Electrolysis of Water

Decomposition Reactions Types of Decomposition Reactions: Types of Decomposition Reactions: Decomposition of carbonates Decomposition of carbonates When heated, some carbonates break down to form an oxide and carbon dioxide. When heated, some carbonates break down to form an oxide and carbon dioxide. CaCO 3  CaO + CO 2 CaCO 3  CaO + CO 2 H 2 CO 3  H 2 O + CO 2 H 2 CO 3  H 2 O + CO 2

Decomposition Reactions Types of decomposition reactions: Types of decomposition reactions: Some metal hydroxides decompose into oxides and water when heated. Some metal hydroxides decompose into oxides and water when heated. Ca(OH) 2  CaO + H 2 O Ca(OH) 2  CaO + H 2 O Note that this is the reverse of a similar combination reaction.

Decomposition Reactions Types of decomposition reactions: Types of decomposition reactions: Metal chlorates decompose into chlorides and oxygen when heated. Metal chlorates decompose into chlorides and oxygen when heated. 2KClO 3  2KCl + 3O 2 2KClO 3  2KCl + 3O 2 Zn(ClO 3 ) 2  ZnCl 2 + 3O 2 Zn(ClO 3 ) 2  ZnCl 2 + 3O 2 Some of these reactions are used in explosives. Some of these reactions are used in explosives.

Decomposition Reactions Some substances can easily decompose: Some substances can easily decompose: Ammonium hydroxide is actually ammonia gas dissolved in water. Ammonium hydroxide is actually ammonia gas dissolved in water. NH 4 OH  NH 3 + H 2 O NH 4 OH  NH 3 + H 2 O Some acids decompose into water and an oxide. Some acids decompose into water and an oxide. H 2 SO 3  H 2 O + SO 2 H 2 SO 3  H 2 O + SO 2

Decomposition Reactions Some decomposition reactions are difficult to predict. Some decomposition reactions are difficult to predict. The decomposition of nitrogen triiodide, NI 3, is an example of an interesting decomposition reaction. The decomposition of nitrogen triiodide, NI 3, is an example of an interesting decomposition reaction.

Nitrogen triiodide

Single Replacement Reactions A metal will replace a metal ion in a compound. A metal will replace a metal ion in a compound. The general form is A + BX  AX + B The general form is A + BX  AX + B A nonmetal will replace a nonmetal ion in a compound. A nonmetal will replace a nonmetal ion in a compound. The general form is Y + BX  BY + X The general form is Y + BX  BY + X

Single Replacement Reactions Examples: Examples: Ni + AgNO 3  Ni + AgNO 3  Nickel replaces the metallic ion Ag +. Nickel replaces the metallic ion Ag +. The silver becomes free silver and the nickel becomes the nickel(II) ion. The silver becomes free silver and the nickel becomes the nickel(II) ion. Ni + AgNO 3  Ag + Ni(NO 3 ) 2 Ni + AgNO 3  Ag + Ni(NO 3 ) 2 Balance the equation: Balance the equation: Ni + 2AgNO 3  2Ag + Ni(NO 3 ) Ni + 2AgNO 3  2Ag + Ni(NO 3 )

Metal Tree

Single Replacement Reactions Not all single replacement reactions that can be written actually happen. Not all single replacement reactions that can be written actually happen. The metal must be more active than the metal ion. The metal must be more active than the metal ion. Aluminum is more active than iron in Al + Fe 2 O 3 in the following reaction: Aluminum is more active than iron in Al + Fe 2 O 3 in the following reaction:

Thermite Reaction

Al + Fe 2 O 3  Al + Fe 2 O 3  Aluminum will replace iron(III) as was seen in the video. Aluminum will replace iron(III) as was seen in the video. Iron(III) becomes Fe and aluminum metal becomes Al 3+. Iron(III) becomes Fe and aluminum metal becomes Al 3+. 2Al + Fe 2 O 3  2Fe + Al 2 O 3 2Al + Fe 2 O 3  2Fe + Al 2 O 3

Single Replacement Reactions An active nonmetal can replace a less active nonmetal. An active nonmetal can replace a less active nonmetal. The halogen (F 2, Cl 2, Br 2, I 2 ) reactions are good examples. The halogen (F 2, Cl 2, Br 2, I 2 ) reactions are good examples. F 2 is the most active and I 2 is the least. F 2 is the most active and I 2 is the least. Cl 2 +2 NaI  2 NaCl + I 2 Cl 2 +2 NaI  2 NaCl + I 2

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

NaOH + CuSO 4

Double Replacement NaOH + CuSO 4  NaOH + CuSO 4  The Na + and Cu 2+ switch places. The Na + and Cu 2+ switch places. Na + combines with SO 4 2- to form Na 2 SO 4. Na + combines with SO 4 2- to form Na 2 SO 4. Cu 2+ combines with OH - to form Cu(OH) 2 Cu 2+ combines with OH - to form Cu(OH) 2 NaOH + CuSO 4  Na 2 SO 4 + Cu(OH) 2 NaOH + CuSO 4  Na 2 SO 4 + Cu(OH) 2 2NaOH + CuSO 4  Na 2 SO 4 + Cu(OH) 2 2NaOH + CuSO 4  Na 2 SO 4 + Cu(OH) 2

CuSO 4 + Na 2 CO 3

Double Replacement CuSO 4 + Na 2 CO 3  CuSO 4 + Na 2 CO 3  Cu 2+ combines with CO 3 2- to form CuCO 3. Cu 2+ combines with CO 3 2- to form CuCO 3. Na + combines with SO 4 2- to form Na 2 SO 4. Na + combines with SO 4 2- to form Na 2 SO 4. CuSO 4 + Na 2 CO 3  CuCO 3 + Na 2 SO 4 CuSO 4 + Na 2 CO 3  CuCO 3 + Na 2 SO 4

Na 2 CO 3 + HCl

Double Replacement Na 2 CO 3 + HCl  Na 2 CO 3 + HCl  Notice that gas bubbles were produced rather than a precipitate. Notice that gas bubbles were produced rather than a precipitate. What was the gas? What was the gas? Write the double replacement reaction first. Write the double replacement reaction first.

Double Replacement Na 2 CO 3 + HCl  Na 2 CO 3 + HCl  Na + combines with Cl - to form NaCl. Na + combines with Cl - to form NaCl. H + combines with CO 3 2- to form H 2 CO 3. H + combines with CO 3 2- to form H 2 CO 3. Na 2 CO 3 + 2HCl  2NaCl + H 2 CO 3 Na 2 CO 3 + 2HCl  2NaCl + H 2 CO 3 H 2 CO 3 breaks up into H 2 O and CO 2. H 2 CO 3 breaks up into H 2 O and CO 2.

Double Replacement The gas formed was carbon dioxide. The gas formed was carbon dioxide. The final balanced reaction is: Na 2 CO 3 + HCl  NaCl + H 2 O + CO 2. The final balanced reaction is: Na 2 CO 3 + HCl  NaCl + H 2 O + CO 2. Balance the equation. Balance the equation. Na 2 CO 3 + 2HCl  2NaCl + H 2 O + CO 2 Na 2 CO 3 + 2HCl  2NaCl + H 2 O + CO 2

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

Combustion Reaction Methane, CH 4, is natural gas. Methane, CH 4, is natural gas. When hydrocarbon compounds are burned in oxygen, the products are water and carbon dioxide. When hydrocarbon compounds are burned in oxygen, the products are water and carbon dioxide. CH 4 + O 2  CO 2 + H 2 O CH 4 + O 2  CO 2 + H 2 O CH 4 + 2O 2  CO 2 + 2H 2 O CH 4 + 2O 2  CO 2 + 2H 2 O

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

Practice Classify each of the following as to type: Classify each of the following as to type: H 2 + Cl 2  2HCl H 2 + Cl 2  2HCl Combination Combination Ca + 2H 2 O  Ca(OH) 2 + H 2 Ca + 2H 2 O  Ca(OH) 2 + H 2 Single replacement Single replacement

Practice 2CO + O 2  2CO 2 2CO + O 2  2CO 2 Combination and combustion Combination and combustion 2KClO 3  2KCl + 3O 2 2KClO 3  2KCl + 3O 2 Decomposition Decomposition

Practice FeS + 2HCl  FeCl 2 + H 2 S FeS + 2HCl  FeCl 2 + H 2 S Double replacement Double replacement Zn + HCl  ? Zn + HCl  ? Single replacement Single replacement Zn + 2HCl  ZnCl 2 + H 2 Zn + 2HCl  ZnCl 2 + H 2

Types of Chemical Reactions Read Chapter 8-2 Read Chapter 8-2 Review nomenclature Review nomenclature Do all of the practice exercises given in class. Do all of the practice exercises given in class.