Ch. 7 & 8 Notes -- Chemical Reactions Chemical equations give information in two major areas: 1. _____________ and ______________ of the reaction. 2. Coefficients of a balanced chemical equation tell us the ______ of the substances involved. Example of a Balanced Chemical Equation: 2H 2 (g) + O 2 (g)  2H 2 O (g) Review: Reactants are on the ______ side of the arrow, and the products are on the __________ side. The arrow means “________”, or “reacts to produce” when read aloud. From our example, hydrogen reacts with oxygen in a ___:___ ratio. The coefficients represent either the number of _________ or molecules present. The coefficients can also represent _________ if the substances are gases. (1 mole = 6.02 x molecules, 1 mole of gas= 22.4 Liters) Reactantsproducts amount left yieldsright 2 1 moles liters

Common Symbols used in Chemical Equations (See Table 8.1) + = used to separate 2 reactants or 2 products from each other → = “yields” or “reacts to produce” = _____________ reaction (like a rechargeable battery) (s) (l) (g) (aq) = phase of matter: (solid, liquid, gas, or “aqueous”) = ___________ supplied to the reaction MnO 2 = a catalyst, (in this case, MnO 2 ), is used to ________ ____ the reaction. = _______ given off as a product = ______ precipitate produced reversible heat speed up gas solid

Decoding Common Chemical Equation Symbols Practice Problems: Describe the following reactions using complete sentences. a) NaHCO 3 (s) + HCl (aq)  NaCl (aq) + H 2 O (l) + CO 2 b) H 2 SO 4 (aq) + BaCl 2 (aq)  HCl (aq) + BaSO 4 (s) c) Write a chemical equation from the following description: “Sodium plus bromine, when heated, reacts to produce solid sodium bromide.” Solidsodium bicarbonateplusaqueoushydrochloric acidyields aqueoussodium chloridepluswaterpluscarbon dioxide gas. Aqueoussulfuric acidplusaqueousbarium chlorideyields aqueoushydrochloric acidplussolid barium sulfate. Na +Br 2  NaBr (s) (s) (l)

Balancing Chemical Equations Why do you have to balance a chemical equation? Law of Conservation of Matter (or Mass): “Matter is neither ____________ nor _______________ in chemical reactions.” During a chemical reaction, atoms are either _________, ______________, or rearranged. The _____________ and type of each atom stays the same. How do you balance a chemical equation? __________________ are placed in front of the substances involved in the chemical reaction to get the same number of atoms of each element on both sides of the equation. This number will multiply the number of atoms there are in a formula. createddestroyed joined separatednumber Coefficients

Rules for Balancing Chemical Equations (1) Coefficients can only be placed ___ _________ of a chemical formula. Practice Problems: How many atoms of each type are indicated in the following compounds? (a) 2 (NH 4 ) 3 PO 4 N= ___ H= ___ P= ___ O= ___ (b) 4 KC 2 H 3 O 2 K= ___ C= ___ H= ___ O= ___ (c) 3 Ca(NO 3 ) 2 Ca= ___ N= ___ O= ___ in front

(2) You cannot change a ________________!! Example : H 2 + O 2  H 2 O To balance oxygen, you cannot change water’s formula to_________! (3) You cannot place the coefficient in the ______________ of a formula!! Example : Al + N 2  AlN To balance nitrogen, you cannot put a 2 in the middle to make _______. (4) Reduce the coefficients to the simplest ____________ ___ ratio. Example: 4H 2 + 2O 2  4H 2 O can be reduced to… __H 2 + __O 2  __H 2 O Rules for Balancing Chemical Equations subscript H2O2H2O2 middle Al2N whole #

(5) Get rid of any ____________! Coefficients must be _________ #’s You can’t have a _______________ of a molecule or atom! Example: 1H 2 + ½O 2  1H 2 O changes to… __ H 2 + __O 2  __H 2 O Rules for Balancing Chemical Equations fractionswhole fraction ()2 x 212

Balancing Equations: “Helpful Hints” a) Balance elements that appear in more than one compound ________. ___(NH 4 ) 2 CO 3  ___NH 3 + ___CO 2 + ___H 2 O b) Balance _____ “___________” as though it were one item as long as the ion stays together as a group on each side of the yields arrow. ___Al + ___CuSO 4  ___Al 2 (SO 4 ) 3 + ___Cu c) If you can’t seem to get it balanced, _________ _________ and begin with a different element the next time, or put a “2” somewhere and then try again. ___Li + ___H 2 O  ___LiOH + ___H 2 d)This is what I’ll constantly be telling you to do if you are stuck and you need my help... “Pick an element to balance. How many are on the left side? How many are on the right side? ________ ____!” ___Fe(OH) 3  ___Fe 2 O 3 + ___H 2 O last 2111 ionchunks 3231 start over 2221 Fix it 231

Balancing Equations: “Helpful Hints” e) My goofy “balancing song” may help: “If there’s a ___ on the left and a ___on the right, you put a ___ on the left and a ___ on the right, (makin’ money!)” ___Al + ___O 2  ___Al 2 O 3 f) If you see only C’s H’s and O’s, balance them in this order: C, H, O. ___C 2 H 2 + ___O 2  ___CO 2 + ___H 2 O /2 ()2 x

Five General Types of Reactions 1) ________________________: A reaction that breaks apart ______ ______________ into simpler substances, (usually two elements or an element and a smaller compound.) General Form:_____  ___ + ___ Examples: H 2 O  _____ + _____ KClO 3  _____ + _____ Remember that “HONClBrIF” elements are diatomic when alone!! Decomposition one compound AX H2H2 O2O2 KCl O2O2 +

Categories of Decomposition (and Composition ) Reactions a) carbonates  metallic oxide + CO 2 CaCO 3  _____ + _____ b) chlorates  metallic chloride + O 2 NaClO 3  _____ + _____ c) hydroxides  metallic oxide + H 2 O Mg(OH) 2  _____ + _____ d) oxy acids  nonmetal oxide + H 2 O H 2 SO 4  _____ + _____ e) binary compounds  2 elements NaCl  _____ + _____ Every time you try to write the formula for a new compound, you must look up the ___________ of the ions and ___________ them if they are different!! Balance it _________ you get all the correct formulas written first! Don’t forget about the HONClBrIF’s! CaOCO 2 NaClO2O2 MgOH2OH2O SO 3 NaCl 2 chargescross AFTER H2OH2O

2) _______________: (sometimes called “Combination” or “Synthesis”) A reaction of _____ __________________, typically a metal and a nonmetal to form ______ ______________. It is the opposite of decomposition. (The same categories of reactions from above apply, just in reverse.) General Form: ___ + ___  _____ Examples: Al + Cl 2  _______ PbO + H 2 O  ______ General Types of Reactions (Continued) Composition two substances one compound AXAX AlCl 3 Pb(OH) 2 + metallic + water oxide  hydroxide 2 elements  binary compound

3) _____________ Replacement: A reaction between ____ ______________ and ___ ____________ that produces a different _____________ and ______________. General Forms: ____ + __  ____ + __ ____ + __  ____ + __ The element that is trying to replace the other must be ________ _______________ than the one it is replacing. You must use the Activity Series to see if the reaction will happen. Table 8.2 _________ ___ = more reactive Elements from ____ to ____ can displace hydrogen in water to form a metallic hydroxide and H 2 gas. General Types of Reactions (Continued) Single one compoundone element compoundelement Y B X A AXAY BXAX more reactive Higher up LiNa + +

Activity Series

Single Replacement Reactions Examples: NaCl + F 2  _____ + _____ FeCl 2 + K  _____ + _____ HCl + Zn  _____ + _____ HCl + Au  _____ + _____ H 2 O + Na  _____ + _____ H 2 O + Fe  _____ + _____ AgNO 3 + Cu  _____ + _____ NaFCl 2 KClFe ZnCl 2 H2H2 no reaction NaOH H2H2 CuNO 3 Ag H(OH) no reaction

4) _______________ Replacement: (sometimes called “Ionic”) A reaction between _____ ________________ that are dissolved in water that produces _____ ________________, one of which is ________________. Water or a gas may be one of the two compounds being produced. General Form: ____ + ____  ____ + ____ You must use the Solubility Chart to see which product is the precipitate. Solubility Chart Key ___ or _____= precipitate Examples: CaCl 2 (aq) + AgNO 3 (aq)  _________ + ________ NaOH (aq) + HCl (aq)  ________ + ________ General Types of Reactions (Continued) Double two compounds insoluble AX (aq) BY (aq) AY (aq) BX (s) IsS Ca(NO 3 ) 2 AgCl (aq) H 2 O (l) NaCl (aq) ++

Double Replacement Reaction

General Types of Reactions (Continued) 5) _________________: A reaction between a Carbon/Hydrogen (and sometimes Oxygen) _________________ with _____. The products are always the same… ________ + ________ This reaction is too easy!! Don’t miss it! General Form: C x H y + O 2  ____ + ____ Examples: C 2 H 2 + O 2  _______ + _______ C 7 H 6 O + O 2  _______ + _______ Combustion compound O2O2 CO 2 H2OH2O H2OH2O H2OH2O H2OH2O

Writing Net Ionic Equations for Double Replacement Reactions A “net ionic equation” only shows the _________ that were used to make the precipitate. Some ions were always dissolved in water. These are called “________________ ions”. (They don’t do anything, so we can ignore them.) Example: CaCl 2 (aq) + 2AgNO 3 (aq)  Ca(NO 3 ) 2 (aq) + 2AgCl (s) Ionic Equation Written as Ions Dissolved in Water: ___ (aq) + ___ (aq) + ___ (aq) + _____ (aq)  ___ (aq) + _____ (aq) + _________ (s) Cancel out the spectator ions, and you are left with the Net Ionic Equation! ________ + _________  __________ ions spectator Ca +2 2Cl − 2Ag + 2NO 3 − Ca +2 2NO 3 − 2AgCl 2Cl − (aq) 2Ag + (aq) 2AgCl (s)

Writing Net Ionic Equations for Double Replacement Reactions Practice Problem: Write the net ionic equation for the following reaction. K 2 CO 3 (aq) + Ba(NO 3 ) 2 (aq)  _________ + _________ Net Ionic Equation = _________________________  ___________ KNO 3 BaCO 3(aq) CO 3 −2 (aq) Ba +2 (aq) +BaCO 3