2 basic types of reactions Good News!Of all the millions of possible chemical reactions, there are only5basic types of reactions
3 Synthesis Two or more reactants combine to form a product: A + B C C O CO2
4 DecompositionThe reverse of synthesis: A compound breaks down into two or more simpler substancesA B CCO C O2
5 Single ReplacementA “single” element replaces another element in a compoundA + BX B + AXNa + AgNO Ag + NaNO3
6 When will single replacement reactions occur? Use Table J for single replacement reactionsThe higher the element is on the table, the more reactive it is. A reactive element wants to react, and form a compound. It will “bump” a less reactive element out of the compound and take its place.
7 Single ReplacementIn this example, Na is more reactive than Ag, so Na bumps Ag out of the nitrate compound and takes its place.Na + AgNO Ag + NaNO3
8 Double ReplacementTwo aqueous ionic compounds (dissolved in water) switch positive ions to produce either a precipitate, a gas, or a molecular compound (like water)AB CD AD CBAgNO3(aq)+ NaCl(aq) AgCl(s) + NaNO3(aq)
9 Double Replacement Use Table F to determine if a precipitate will form AB CD AD CBAgNO3(aq)+ NaCl(aq) AgCl(s) + NaNO3(aq)
10 Combustion Hydrocarbon and oxygen yields carbon dioxide and water and heatCH O CO2 + H2O + heat
11 Balancing EquationsMass is always conserved in a chemical reaction
13 H O H2OIs mass conserved in this equation?NO!Reactants:Products:2 H1 O2 H2 O
14 How to Balance an equation Step 1. Place a box around all compoundsH O H2OStep 2. DO NOT make any changes to thecompounds inside each box!!!!!!
15 How to Balance an equation Step 3. Place coefficients in front of eachbox to show conservation of mass.Everything inside the box will be multipliedby this number.H O H2O2Products:Reactants:4 H2 O2 H2 O
16 How to Balance an equation Step 3. Place coefficients in front of eachbox to show conservation of mass.Everything inside the box will be multipliedby this number.2H O H2O2Products:Reactants:4 H2 O4 H2 O
17 How to Balance an equation Step 4. Count the types of atoms on bothsides of the equation. The atoms on the reactantside must be the same as the atoms on theproduct side2H O H2O2Products:=Reactants:4 H2 O4 H2 O
18 Helpful Hints for balancing Balance one type of atom at a timeBalance atoms that appear only once on each side of the equation firstBalance oxygen and hydrogen lastIt is an iterative process. Be Patient!
20 Unknown reactants or products Since mass is always conserved, this principle can be used to find unknown parts of a chemical reactionCount the atoms on both sides of the equation and determine what atoms are missing from one side……
21 Unknown reactants or products 2 Na + 2H2O X NaOHReactants:Products:2 NaH2 O2 Na2 H2 OX must be H2
22 Unknown reactants or products 2 Na + 2H2O H NaOHReactants:Products:2 NaH2 O2 Na2 H2 OX must be H2
23 Finding Missing MassIn a similar way to finding missing compounds, missing mass can also be found since mass is always conserved.
24 Given the following balanced equation: 2 KClO KCl O2If 103 g of KClO3 decomposed to form 62.7 g of KCl,how many grams of oxygen gas are formed?
25 2 KClO KCl O2103 g = g x103 g – 62.7 g = x40.3 g = x
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