Types of Chemical Reactions

Types of Reactions We will talk about five types of chemical reactions: Synthesis reactions Decomposition reactions Single displacement reactions Double displacement reactions Combustion reactions You need to be able to identify the type of reaction and predict the product(s)

1. Synthesis Reactions two substances (generally elements) combine and form a compound reactant + reactant  1 product A + B  AB Example: carbon + oxygen  carbon dioxide C + O 2  CO 2

Synthesis Reactions

Practice Predict the products. Write and balance the following synthesis reaction equation. Sodium metal reacts with chlorine gas Na (s) + Cl 2(g)  NaCl (s) 2Na (s) + Cl 2 (g)  2NaCl (s)

2. Decomposition Reactions occur when a compound breaks up into the elements or into a few simpler compounds reactant  product + product AB  A + B Example: water  hydrogen + oxygen H 2 O  H 2 + O 2 2 H 2 O  2H 2 + O 2

Decomposition Reactions

Practice Predict the products. Write and balance the following decomposition reaction equation: Lead (IV) oxide decomposes PbO 2 (s)  Pb (s) + O 2 (g)

3. Single Displacement Reactions occur when one element replaces another in a compound. element + compound  product + product A + BC  AC + B (if A is a metal) OR A + BC  BA + C (if A is a non-metal) (note: the cation always goes first!)

A + BC  AC + B

Single Displacement Reactions

Practice Write and balance the following single replacement reaction equation: Zinc metal reacts with aqueous hydrochloric acid (Zinc can form 2 bonds) Zn (s) + 2HCl (aq)  ZnCl 2 + H 2(g) HCl is hydrochloric acid, (aq) means aqueous, or dissolved in water

4. Double Displacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound c ompound + compound  product + product AB + CD  AD + CB

Double Displacement Reactions first and last ions go together, inside ions go together Example: AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq) Example: K 2 SO 4(aq) + Ba(NO 3 ) 2(aq)  2KNO 3(aq) + BaSO 4(s)

5. Combustion Reactions occur when a hydrocarbon reacts with oxygen gas. always forms carbon dioxide and water vapour as products

Combustion Reactions Hydrocarbon + Oxygen CO 2 + H 2 O + Energy Hydrocarbon + Oxygen  CO 2 + H 2 O + Energy incomplete burning may result in undesirable by- products like carbon monoxide

Edgar Allen Poe’s drooping eyes and mouth are potential signs of CO poisoning

Combustion Example: combustion of pentane C 5 H 12 (l) + 8O 2 (g)  5CO 2 (g) + 6H 2 O (g)