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Chapter 10. Chemical reactions. Evidence of chemical rxns: Change in enthalpy Change in color Formation of a gas Formation of a ppt. Chemical reaction- represented by an equation. 2 C 2 H 2 (g) + 5O 2 (g) 4CO 2 (g) + 2H 2 O (l). Reactants. Products. - PowerPoint PPT Presentation
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Chemical reactions
• Evidence of chemical rxns:– Change in enthalpy– Change in color– Formation of a gas– Formation of a ppt
Chemical reaction- represented by an equation
2 C2H2 (g) + 5O2 (g) 4CO2 (g) + 2H2O(l)
Reactants
Products
(aq) a substance dissolved in water
Equations must be balanced
Start with a skeleton eqn
Never change a subscript
Exercises Pg 279 + 282
Synthesis Rxns - 2 or more substances combine
2Na (s) + Cl2 (g) 2NaCl (s)
Element or compound + element or compound compound
Combustion Rxns - oxidation reactions—reacting with oxygen
Oxidation of a hydrocarbon
Produces CO2 (g) + H2O (g)
CH4 (g) + 2O2 (g) CO2 (g) + 2H2O (g)
Single Displacement Rxns - one element displaces another in a compoundBr2 (l) + 2KI (s) 2KBr (aq) + I2 (s)
2Al (cr) + 3ZnCl2 (cr) 2AlCl3 (cr) + 3Zn (cr)
Note that a nonmetal replaces a nonmetal and a metal replaces a metal, charges add
up to zero, and you must use figure 10-10.Element + Compound Element + Compound
Double Displacement Rxns
HCl (aq) + NaOH (aq) NaCl (aq) + HOH (l)
compound + compound compound + compound
Decomposition Rxns - break up into simple substances when energy is supplied(Heat, light, mechanical shock, or
electricity)H2CO3 (aq) H2O(l) + CO2 (g)
2H2O (l) 2H2 (g) + O2 (g)
Compound 2 or more elements or compounds
Rxns in Aqueous Soln’s
– Complete chemical eqn– Complete ionic eqn– Net ionic eqn (exclude spectator ions)
• Rxns that form ppts
Quiz
• Lead (II) nitrate reacts with potassium iodide - Lead (II) iodide forms a ppt
• Write the chemical equation
• Write the complete ionic equation
• Id all spectators
• Write the net ionic equation
Five Types of Chemical Reactions
1. Single Displacement
element + compoundelement + compound
2. Double Displacement
compound AB + compound CDcompound AD +compound CB
3. Decomposition
compoundtwo or more elements or compounds
4. Synthesis
element or compound + element or compound compound
Rxns in Aqueous soln’s
• Rxns that form ppts
• Complete eqn
• Complete ionic eqn
Spectator ions
Net ionic eqn
Potassium carbonate and manganese (V) chloride
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