Types of Chemical Reactions

Evidence of Chemical Reactions Change in colour Change in odour Formation of a gas Formation of a precipitate Release or absorption of energy (e.g. heat or light)

Types of Chemical Reactions We will learn about 6 types of chemical reactions Synthesis Decomposition Combustion Single Displacement Double Displacement Neutralization

Subscripts for States of Matter We can identify the physical state of a substance using subscripts (s) = solid (g) = gas (l) = pure liquid (aq) = aqueous solution (dissolved in water)

Synthesis Reactions A + B  AB 2H2(g) + O2(g)  2H2O(l) Smaller atoms/molecules combine to form larger molecules A + B  AB 2H2(g) + O2(g)  2H2O(l)

Synthesis Reaction +

Decomposition Reaction The splitting of a large molecule into elements or smaller molecules AB  A + B Complimentary to synthesis reaction 2H2O(l)  2H2(g) + O2(g)

Decomposition Reaction +

C4H10(l) + O2(g)  CO2(g) + H2O(l) + heat Combustion Fuel (hydrocarbons) burned in the presence of oxygen to produce a carbon dioxide, water and heat energy CxHy + O2  CO2 + H2O + heat C4H10(l) + O2(g)  CO2(g) + H2O(l) + heat

Incomplete Combustion Occurs when fuel is not completely converted into carbon dioxide and water Can result in the production of toxic carbon monoxide C4H10(l) + O2(g)  C(s) + CO(g) + CO2(g) + H2O(g) soot poisonous

Mg(s) + 2AgNO3(aq)  2Ag(s) + Mg(NO3)2(aq) Single Displacement One element replaces another element from a compound A + BC  AC + B Mg(s) + 2AgNO3(aq)  2Ag(s) + Mg(NO3)2(aq) Note: A metal can only replace a metal and a nonmetal can only replaces a nonmetal

Single Displacement

Single Displacement + +

The Activity Series If the single element is above the element in the compound, a single displacement reaction will occur.

Examples aluminum + nickel (II) chloride lead + zinc nitrate fluorine + sodium bromide

Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq) Double Displacement Positive ions (cations) in different compounds replace each other AB + CD  AD + CB Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq)

Double Displacement

Double Displacement + +

Solubility Rules Most double displacement reactions involve aqueous solutions of ionic compounds For a reaction to occur, a precipitate (insoluble solid) must form To predict which ionic compounds will be soluble, and which will form precipitates (insoluble) we must use the solubility rules: All compounds with nitrate (NO3-) are soluble All compounds with ammonium (NH4+) are soluble All compounds with group 1 metals are soluble Most other compounds are insoluble (will form a precipitate)

Solubility Table …Or use a solubility table

Examples sodium carbonate + barium nitrate  lithium hydroxide + ammonium chlorate 

HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) Neutralization A special type of double displacement reaction Acid + Base  Salt + H2O (ionic compound) HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)

Practice Makes Perfect! Read p. 111, 114-115,118-123,138-139 Try some problems.