Wednesday December 2, 2009 (Discussion)

Bell Ringer Write both the word equation and balanced formula equation for the following reaction. Solid zinc (II) sulfide reacts with oxygen gas to produce solid zinc (II) oxide and gaseous sulfur dioxide.

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Assignments Currently Open AssignmentPage Date Issued Date Into GradeSpeed Last Day to Turn In WS: Intermolecular Forces, Hydrogen Bonding, Metals 17311/1611/3012/2 WS: Building Ionic Compounds 17711/1712/112/8 WS: Building Molecular Compounds 18111/1912/312/10 WS: Chemical Reactions and Equations 18912/112/812/15

Sample Problem Aluminum sulfate and calcium hydroxide are used in a water-purification process. When added to water, they dissolve and react to produce two insoluble products, aluminum hydroxide and calcium sulfate. These products settle out, taking suspended solid impurities with them. Write a balanced chemical equation for the reaction. Al 2 (SO 4 ) 3 + Ca(OH) 2 → Al(OH) 3 + CaSO

Types of Chemical Reactions Synthesis Reactions Decomposition Reactions Single-Replacement Reactions Double-Replacement Reactions Combustion Reactions

Synthesis Reactions In synthesis reactions (also called addition reactions), two or more substances combine to form a new compound. A + X → AX 2Mg + O 2 → 2MgO 2H 2 + O 2 → 2H 2 O 16Rb + S 8 → 8Rb 2 S CaO + H 2 O → Ca(OH) 2

Decomposition Reactions In a decomposition reaction, a single compound undergoes a reaction that produces two or more simpler substances. AX → A + X 2H 2 O → 2H 2 + O 2 2HgO → 2Hg + O 2 2KClO 3 → 2KCl + 3O 2

Single-Replacement Reactions In a single-replacement reaction, one element replaces a similar element in a compound. A + BX → AX + B Mg + 2HCl → MgCl 2 + H 2 Cl 2 + 2KBr → 2KCl + Br 2 2Al + 3Pb(NO 3 ) 2 → 3Pb + 2Al(NO 3 ) 3

Double-Replacement Reactions In a double-replacement reaction, the ions of two compounds exchange places in an aqueous solution to form two new compounds. AX + BY → AY + BX HCl + NaOH → NaCl + H 2 O 2KI + Pb(NO 3 ) 2 → PbI 2 + 2KNO 3 FeS + 2HCl → H 2 S + FeCl 2

Combustion Reactions In a combustion reaction, a carbon- containing substance combines with oxygen to produce carbon dioxide and water, and releasing a large amount of energy in the form of light and heat. CX + O 2 → CO 2 + H 2 O CH 4 + 2O 2 → CO 2 + 2H 2 O C 3 H 6 + 5O 2 → 3CO 2 + 4H 2 O

Activity Series The ability of an element to react is called the element’s activity. The ability of an element to react is called the element’s activity. An activity series is a list of elements organized according to the ease with which the elements undergo certain chemical reactions. An activity series is a list of elements organized according to the ease with which the elements undergo certain chemical reactions. For metals, greater activity means a greater ease of loss of electrons, to form positive ions. For metals, greater activity means a greater ease of loss of electrons, to form positive ions. For nonmetals, greater activity means a greater ease of gain of electrons, to form negative ions. For nonmetals, greater activity means a greater ease of gain of electrons, to form negative ions.

Activity Series The order in which the elements are listed in an activity series is usually determined by single- replacement reactions. The order in which the elements are listed in an activity series is usually determined by single- replacement reactions. The most active element, placed at the top in the series, can replace each of the elements below it from a compound in a single- replacement reaction. The most active element, placed at the top in the series, can replace each of the elements below it from a compound in a single- replacement reaction. An element farther down can replace any element below it but not any above it. An element farther down can replace any element below it but not any above it. Activity series are used to help predict whether certain chemical reactions will occur. Activity series are used to help predict whether certain chemical reactions will occur.

Activity Series See Table 8-3. See Table 8-3. –Ex) According to the activity series for metals, aluminum replaces zinc.  We, therefore, can predict that the following reaction does occur:  2Al + 3ZnCl2 → 3Zn + 2AlCl 3 –Ex) Cobalt cannot replace sodium  We, therefore, can predict that the following reaction does not occur:  Co + 2NaCl → no reaction

Activity Series Sample Problem Sn + O 2 → SnO 2 Any metal more active than silver will react with oxygen to form an oxide. Tin is above silver in the activity series, therefore a reaction will occur. The product will be tin oxide, either SnO or SnO 2

Activity Series Sample Problem Cd + Pb(NO 3 ) 2 → Pb + Cd(NO 3 ) 2 An element will replace any element below it in the activity series from a compound in aqueous solution. Cadmium is above lead, therefore a reaction will occur to produce lead and cadmium nitrate.

Activity Series Sample Problem Cu + HCl → no reaction Any metal more active than hydrogen will replace hydrogen from an acid. Copper is not above hydrogen in the series, therefore no reaction will occur.

Activity Series Question How is the activity series useful in predicting chemical behavior? It helps predict whether a chemical reaction will occur and what the product(s) of the reaction will be.

Activity Series Question Based on the activity series, predict whether the following reaction will occur? Ni + H 2 O → No

Activity Series Question Based on the activity series, predict whether the following reaction will occur? Br 2 + KI → 2KBr + I 2

Activity Series Question Based on the activity series, predict whether the following reaction will occur? Au + HCl → No

Activity Series Question Based on the activity series, predict whether the following reaction will occur? Cd + HCl → CdCl 2 + H 2 2

Activity Series Question Based on the activity series, predict whether the following reaction will occur? Mg + Co(NO 3 ) 2 → Mg(NO 3 ) 2 + Co

Continue Worksheet Chemical Reactions and Equations (Page 189)