1 Section 11.2 p. 330 Types of Chemical Reactions

2 Types of Reactions l 6 major types. l predict the products l predict whether or not they will happen at all l How? We recognize them by their reactants

3 #1 - Combination Reactions l Combine = put together l 2 substances combine to make one cmpd (also called “synthesis”) Ca + O 2  CaO SO 3 + H 2 O  H 2 SO 4 l predict products, especially if reactants are 2 elements Mg + N 2  Mg 3 N 2 (symbols, charges, cross)

4 Complete and balance: Ca + Cl 2  Fe + O 2  (assume iron (II) oxide is the product) Al + O 2  l Remember first step…write correct formulas – you can still change subscripts at this point, but not while balancing! l Then balance by changing just coefficients only

5 #1 – Combination Reactions l Additional Notes: a) Some nonmetal oxides react with H 2 O - produces acid: SO 2 + H 2 O  H 2 SO 3 b) Some metallic oxides react with H 2 O - produces base: CaO + H 2 O  Ca(OH) 2 (how “acid rain” forms)

6 #2 - Decomposition Reactions l decompose = fall apart l one reactant breaks apart into 2 or more elements or cmpds l NaCl Na + Cl 2 l CaCO 3 CaO + CO 2 l Note: energy (heat, sunlight, electricity, etc.) usually required

7 #2 - Decomposition Reactions l predict products if binary cmpd (made of 2 elements) –It breaks apart into the elements: lH2OlH2O l HgO

8 #3 - Single Replacement Reactions l One element replaces another (new dance partner) l Reactants must be an element & cmpd l Products will be a different element and different cmpd Na + KCl  K + NaCl F 2 + LiCl  LiF + Cl 2 (Cations switched) (Anions switched)

9 #3 Single Replacement Reactions l Metals replace other metals (they can also replace H) K + AlN  Zn + HCl  l Think of water as: HOH –Metals replace first H, then combines w/ hydroxide (OH). Na + HOH 

10 #3 Will a single replacement reaction occur? l can even tell whether or not single replacement rxn will happen: –b/c some chemicals more “active” than others –More active replaces less active l Look at Activity Series of Metals –Higher on list replaces lower

11 The “Activity Series” of Metals Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead Hydrogen Bismuth Copper Mercury Silver Platinum Gold 1)Metals can replace other metals, if they are above metal trying to replace (i.e. Zn will replace Pb) 2)Metals above H can replace H in acids. 3)Metals from Na upward can replace hydrogen in H 2 O Higher activity Lower activity

12 The “Activity Series” of Halogens Fluorine Chlorine Bromine Iodine Halogens can replace other halogens in compounds, if they are above halogen they are replacing 2NaCl (s) + F 2(g)  2NaF (s) + Cl 2(g) MgCl 2(s) + Br 2(g)  ??? No Reaction! ??? Higher Activity Lower Activity

13 #3 Single Replacement Reactions Practice: Fe + CuSO 4  Pb + KCl  Al + HCl 

14 #4 - Double Replacement Reactions l Two things replace each other. –Reactants must be two ionic compounds, in aqueous solution NaOH + FeCl 3  –positive ions change place (dance partners) NaOH + FeCl 3  Fe +3 OH - + Na +1 Cl -1 = NaOH + FeCl 3  Fe(OH) 3 + NaCl

15 #4 - Double Replacement Reactions l Have certain “driving forces”, or reasons –only happens if one product: a) doesn’t dissolve in water & forms a “precipitate”, or b) is gas that bubbles out, or

16 Complete and balance: l assume all of the following reactions actually take place: CaCl 2 + NaOH  CuCl 2 + K 2 S  KOH + Fe(NO 3 ) 3 

17 How to recognize which type? l Look at the reactants: E + E =Combination C =Decomposition E + C =Single replacement C + C =Double replacement

18 #5 – Combustion Reactions l Combustion means “add oxygen” l Normally, a cmpd composed of only C, H, (and maybe O) is reacted with oxygen – called “burning” l Complete combustion, products are CO 2 and H 2 O l If incomplete, products are CO or C and H 2 O

19 Combustion Reaction Examples: C 4 H 10 + O 2  C 6 H 12 O 6 + O 2 

20 #6 – Acid Base l Acid with a base produces a salt and water l The cation in the salt comes from the base; the anion come from the acid

21 Examples of Acid/Base l HCl (aq) + Ca(OH) 2 (aq)  CaCl 2 (aq) + H 2 O (l) Acid Base Salt Water l H 2 SO 4 (aq) + Fe(OH) 3  Fe 2 (SO 4 ) 3 (aq)  H 2 O Acid Base Salt Water

22 Practice Examples: H 2 + O 2  H 2 O  Zn + H 2 SO 4  HgO  KBr + Cl 2  AgNO 3 + NaCl  Mg(OH) 2 + H 2 SO 3 

23 SUMMARY: An equation... l Describes a rxn l Must be balanced (follows the Law of Conservation of Mass) l only balance by changing coefficients l special symbols to indicate physical state, catalyst or energy required, etc.

24 Reactions l 5 major types l We can tell what type they are by looking at reactants l Single Replacement happens based on the Activity Series l Double Replacement happens if one product is: 1) a precipitate (an insoluble solid), 2) water (a molecular compound), or 3) a gas