The Abbreviated Version Balancing Equations The Abbreviated Version

What is a Chemical Equation? An equation is a short-hand way of writing a chemical reaction. Reactants are on the left, products are on the right. Mg + 2HCl  MgCl2 + H2 reactants products

How is this Accomplished? This is accomplished by adding coefficients in front of the substances in the equation.

Tips for Balancing Equations 1. Balance metals first. 2. Balance nonmetals except H and O. 3. If polyatomic ions are conserved in the reaction, then try balancing them as a unit. 4. Balance any remaining H’s and O’s.

Some practice problems: Here are some practice problems. 1. __NaCl + __BeF2 --> __NaF + __BeCl2 2. __FeCl3 + __Be3(PO4)2 --> __BeCl2 + __FePO4

3. __AgNO3 + __LiOH --> __AgOH + __LiNO3 4. __CH4 + __O2 --> __CO2 + __H2O 5. __Mg + __Mn2O3 --> __MgO + __Mn

7. Na + H2O  NaOH + H2 8. H2SO4 + Ca(OH)2  CaSO4 + H2O

Types of Chemical Reactions There are 5 overall types of chemical reactions: 1. Synthesis or Combination 2. Decomposition 3. Single Replacement 4. Double Replacement 5. Combustion

Synthesis: A + B  AB Examples: H2(g) + Cl2(g) ----> 2HCl(g) C(s) + O2(g) ----> CO2(g) CaO(s) + H2O(l) ----> Ca(OH)2(s)

Decomposition: AB  A + B C12H22O11(s) ---->12C(s) + 11H2O(g) Pb(OH)2(s) ----> PbO(s) + H2O(g) 2Ag2O(s) ----> 4Ag(s) + O2(g)

Single Replacement: A+ BC  B + AC Zn(s) + H2SO4(aq) ----> ZnSO4(aq) + H2(g) 2Al(s) + 3CuCl2(aq) ---> 2AlCl3(aq) + 3Cu(s) Cl2(g) + KBr(aq) ----> KCl(aq) + Br2(l)

Single Replacement Reactions follow the Activity Series

The element by itself has to be more reactive than the one it is trying to replace. Examples: Mg + Zn(NO3)2  Mg + AgNO3  Mg + LiNO3  Zn + H2SO4  Na + H2O  Sn + NaNO3  Cl2 + NaBr 

Double Replacement: AB + CD  AD + CB AgNO3(aq) + NaCl(aq) ----> AgCl(s) + NaNO3(aq) ZnBr2(aq) + 2AgNO3(aq) ----> Zn(NO3)2(aq) + 2AgBr(s) H2SO4(aq) + 2NaOH(aq) ----> Na2SO4(aq) + 2H2O(l)

Special Type of Double Replacement: Neutralization A neutralization reaction occurs between an acid and a base. A base is a metallic hydroxide, such as NaOH, KOH, Ca(OH)2, Al(OH)3, etc. An acid and a base always react to form a salt and water.

Example: HCl + NaOH  NaCl + HOH H2SO4 + Mg(OH)2  MgSO4 + H2O H3PO4 + Al(OH)3 

Combustion: Burning (add O2) CH4(g) + 2O2(g) ----> 2H2O(g) + CO2(g) C2H6(g) + O2(g) ----> H20(g) + CO2(g) C3H8(g) + O2(g) ----> H2O(g) + CO2(g) H2(g) + O2(g) ----> H2O(g) Mg(g) + O2(g) ----> MgO(s)

Another type of reaction: oxidation-reduction or redox In these, the charges on some of the atoms involve change because of an electron transfer. Oxidation Is Loss of electrons. Reduction Is Gain of electrons. Remember “OIL RIG”

When oxidation occurs, the charge on the atom or ion is increased. When reduction occurs, the charge on the atom or ion is decreased. One thing to remember: The charge on an element by itself is 0.

Examples: Fe+2  Fe+3 + e- Cl2 + 2e-  2Cl- Fe+3 + e-  Fe+2 Cu+2 + 2e-  Cu Zn  Zn+2 + 2e-