 Mass is never created or destroyed-ALL must be conserved and accounted for during a chemical reaction  The same number of atoms of reactant elements must equal the atoms of product elements

 To write a balanced chemical equation, first write the skeleton equation. Then use coefficients to balance the equation so that it obeys the law of conservation of mass. 11.1

 Some elements exist naturally in pairs, as diatomic molecules. You will be expected to memorize these: Br 2, I 2, N 2, Cl 2, H 2, O 2, F 2.

 Soild: (s)  Examples: S (s), Na (s), Cu (s)  Liquid: (l)  Examples: H 2 O (l), C 4 H 10(l)  Gas: (g)  Examples: O 2(g), Cl 2(g), CH 4(g)  Aqueous: (aq) – Dissolved in water.  Examples: NaCl (aq), HF (aq), BaCl 2(aq)

There are five types of chemical reactions: 1. Synthesis reactions 2. Decomposition reactions 3. Single displacement reactions 4. Double displacement reactions 5. Combustion reactions Unit objective: identify the type of reaction and predict the product(s).

Steps for doing reaction problems: 1. Identify the type of reaction. 2. Predict the product(s) using the type of reaction as a model. 3. Check for diatomics. (BrINClHOF) 4. Balance the equation.

Synthesis reactions occur when two substances (generally elements) combine to form a compound. reactant + reactant  1 product Basically: A + B  AB Example: 2H 2 + O 2  2H 2 O Example: C + O 2  CO 2

Another example of synthesis:

Predict the products. Write and balance the following synthesis reaction equations. Sodium metal reacts with chlorine gas Na (s) + Cl 2(g)  Solid Magnesium reacts with fluorine gas Mg (s) + F 2(g)  Aluminum metal reacts with fluorine gas Al (s) + F 2(g) 

Decomposition reactions occur when a compound breaks up into the elements or into a few simpler compounds 1 Reactant  Product + Product In general: AB  A + B Example: 2 H 2 O  2H 2 + O 2 Example: 2 HgO  2Hg + O 2

Another view of a decomposition reaction:

AB  A + B

Predict the products. Then, write and balance the following decomposition reaction equations: Solid Lead (IV) oxide decomposes PbO 2(s)  Aluminum nitride decomposes AlN (s) 

Identify the type of reaction for each of the following synthesis or decomposition reactions, and write the balanced equation: H 2(g) + O 2(g)  BaCO 3(s)  Zn (s) + S (s)  NH 3(g) + H 2 CO 3(aq)  NI 3(s) 

Single Replacement Reactions occur when one element replaces another in a compound. A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-). element + compound  element + compound A + BC  AC + B (if A is a metal) OR A + BC  BA + C (if A is a nonmetal) (remember the cation always goes first!) When H 2 O splits into ions, it splits into H + and OH - (not H+ and O -2 !!)

Another view:

Example: Zn + CuCl 2  Zn Cl Cu + General: AB + C  AC + B Cl Zn Cu + LIKE replaces LIKE

Activity Series lists metals in order of decreasing reactivity. As a general rule, more reactive metals replace less reactive metals in a compound Li K Ba Ca Na Mg Al Zn Fe Cd Ni Sn Pb H Cu Hg Ag Au Li K Ba Ca Na Mg Al Zn Fe Cd Ni Sn Pb H Cu Hg Ag Au

Write and balance the following single replacement reaction equation: Zinc metal reacts with aqueous hydrochloric acid: Zn (s) + HCl (aq)  ZnCl 2 + H 2(g) Note: Zinc replaces the hydrogen ion in the reaction 2

Sodium chloride solid reacts with fluorine gas NaCl (s) + F 2(g)  NaF (s) + Cl 2(g) Note that fluorine replaces chlorine in the compound Aluminum metal reacts with aqueous copper (II) nitrate Al (s) + Cu(NO 3 ) 2(aq)  22

Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound Compound + compound  compound+ compound AB + CD  AD + CB

 Solubility rules-  The formation of a precipitate is a driving force of a double replacement reaction  When you predict the products of a double replacement reaction, you must indicate which product is the precipitate using the solubility rules  If both products are soluble, the reaction will not occur- all ions will remain in solution

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

Predict the products. Balance the equation  HCl (aq) + AgNO 3(aq)   CaCl 2(aq) + Na 3 PO 4(aq)   Pb(NO 3 ) 2(aq) + BaCl 2(aq)   FeCl 3(aq) + NaOH (aq)   H 2 SO 4(aq) + NaOH (aq)   KOH (aq) + CuSO 4(aq) 

Combustion reactions occur when a fuel reacts with oxygen gas, which produces heat! Fuel + O 2 (+ Heat)  Product

Hydrocarbon Combustion: C x H y + O 2  CO 2 + H 2 O Products in combustion are ALWAYS carbon dioxide and water. (although incomplete burning does cause some by- products like carbon monoxide) Combustion is used to heat homes (CH 4 )and run automobiles (octane: C 8 H 18 )

Edgar Allen Poe’s drooping eyes and mouth are potential signs of CO poisoning.

Example C 5 H 12 + O 2  CO 2 + H 2 O Write the products and balance the following combustion reaction: C 10 H 22 + O 2  568

State the type, predict the products, and balance the following reactions: 1. BaCl 2 + H 2 SO 4  2. C 6 H 12 + O 2  3. Zn + CuSO 4  4. Cs + Br 2  5. FeCO 3 