Chemical Reactions

Types of Reactions  Synthesis reactions  Decomposition reactions  Single displacement reactions  Double displacement reactions

CO……. Types of Reactions  Combustion reactions  decomposition reactions  precipitation reactions  neutralization reactions o acid o base  oxidation-reduction reaction You need to be able to identify each type.

1. Synthesis Example C + O 2 OO C +  OO C H 2 + 1/2 O 2 H 2 O General: A + B  AB

Ex. Synthesis Reaction EXPLOSIVE ??????

Practice Predict the products. Na (s) + Cl 2(g)  Mg (s) + F 2(g)  Al (s) + F 2(g)  NaCl (s) MgF 2(s) AlF 3(s) Now, balance them. ?

SOLUTION Na (s) + Cl 2(g)  Mg (s) + F 2(g)  Al (s) + F 2(g)  NaCl (s) MgF 2(s) AlF 3(s)

2. Decomposition Example: NaCl General: AB  A + B Cl Na Cl + Na 1/2 2

Ex. Decomposition Reaction

3. Single Displacement Example: Zn + CuCl 2  Zn Cl Cu + General: AB + C  AC + B Cl Zn Cu + Zn was oxidized Went from neutral (0) to (+II ) Cu was reduced Went from (+II) to Neutral (0)

Ex. Single Replacement Reaction

Single Replacement Reactions Write and balance the following single replacement reaction equation: Zn (s) + HCl (aq)  ZnCl 2 + H 2(g) 2 NaCl (s) + F 2(g)  NaF (s) + Cl 2(g) Al (s) + Cu(NO 3 ) 2(aq)  2 2 Cu (s) + Al(NO 3 ) 3(aq )

4. Double displacement Example: MgO + CaS General:AB + CD  AD + CB S O  Mg Ca + O S Mg Ca +

Double Replacement Reactions Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together Example: AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq) Another example: K 2 SO 4(aq) + Ba(NO 3 ) 2(aq)  KNO 3(aq) + BaSO 4(s) 2

Practice Predict the products. 1.HCl (aq) + AgNO 3(aq)  2.CaCl 2(aq) + Na 3 PO 4(aq)  3.Pb(NO 3 ) 2(aq) + BaCl 2(aq)  4.FeCl 3(aq) + NaOH (aq)  5.H 2 SO 4(aq) + NaOH (aq)  6.KOH (aq) + CuSO 4(aq) 

5. Combustion Reactions a. Combustion reactions hydrocarbon reacts with oxygen gas. This is also called burning!!!  In order to burn something you need the 3 things in the “fire triangle”: 1)Fuel (hydrocarbon) 2) Oxygen 3) Something to ignite the reaction (spark)

Combustion Reactions In general: C x H y + O 2  CO 2 + H 2 O + heat Products are ALWAYS carbon dioxide and water. (although incomplete burning does cause some by- products like carbon monoxide) Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C 8 H 18 )

Combustion Example C 5 H 12 + O 2  CO 2 + H 2 O H.W:. Write the products and balance the following combustion reaction: C 10 H 22 + O 2  ????? 5 6 8

Precipitation Reactions The process of separating a substance from a solution as a solid. AgNO 3 + NaCl ---> AgCl + NaNO 3 precipitate

Neutralization Reactions acid base salt Household acids and Bases

Neutralization Reactions Acid  Any of a large class of sour-tasting substances whose aqueous solutions are capable of turning blue litmus indicators red, of reacting with and dissolving certain metals to form salts, and of reacting with bases or alkalis to form salts.  Substance that donates H + ions to solution

Neutralization Reactions Base  Any of a large class of compounds, including the hydroxides and oxides of metals, having a bitter taste, a slippery solution, the ability to turn litmus blue, and the ability to react with acids to form salts.  Substance that donates a OH -1 ion to solution

Neutralization Reactions salt  The term salt is also applied to substances produced by the reaction of an acid with a base, known as a neutralization reaction.  Salts are characterized by ionic bonds, relatively high melting points, electrical conductivity when melted or when in solution, and a crystalline structure when in the solid state.

Neutralization Reactions acid + base ---> “salt” + water

Neutralization Reactions acid + base ---> “salt” + water HCl + NaOH ---> NaCl + H 2 O

Neutralization Reactions acid + base ---> “salt” + water H 2 SO 4 + 2KOH ---> K 2 SO 4 + 2H 2 O

Strong vs. Weak Acids and Bases  strong - completely ionized  weak - partially ionized

Oxidation-Reduction Reaction Oxidation - loss of electrons Reduction - gain of electrons Redox reaction oxidizing agent - substance that causes oxidation reducing agent - substance that cause reduction

Decomposition Reactions Separation into constituents by chemical reaction.

Homogenous Equilibrium  Consider colorless frozen N 2 O 4. At room temperature, it decomposes to brown NO 2 : N 2 O 4 (g) 2NO 2 (g).  At some time, the color stops changing and we have a mixture of N 2 O 4 and NO 2.  Chemical equilibrium is the point at which the concentrations of all species are constant.

The Equilibrium Constant For a general reaction in the gas phase aA + bB ═ cC+ dD the equilibrium constant expression is Keq = p c C p d D p a A p b B where K eq is the equilibrium constant.

The Equilibrium Constant For a general reaction aA +Bb ═ cC + dD the equilibrium constant expression for everything in solution is K eq = [C] c [D] d [A] a [B] b where K eq is the equilibrium constant.

Homogenous Equilibrium At equilibrium, as much N 2 O 4 reacts to form NO 2 as NO 2 reacts to re-form N 2 O 4 : The double arrow implies the process is dynamic. Consider Forward reaction: A  B Rate = k f [A] Reverse reaction: B  A Rate = k r [B] At equilibrium k f [A] = k r [B].

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