BALANCING EQUATIONSAND TYPES OF CHEMICAL REACTIONS

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?

Chemical equations are balanced by adding coefficients in front of the substances in the equation.

1 MgF2 + 1 Li2CO3 1 MgCO3 + 2 LiF

Never change the subscript to balance equations

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 2NaCl + BeF2 2NaF + BeCl2

2. __FeCl3 + __Be3(PO4)2 --> __BeCl2 + __FePO4

2FeCl3 + Be3(PO4)2 --> 3BeCl2 + 2FePO4

3. __AgNO3 + __LiOH --> __AgOH + __LiNO3

AgNO3 + LiOH --> AgOH + LiNO3

4. __CH4 + __O2 --> __CO2 + __H2O CH4 + 2O2 --> CO2 + 2H2O

5. __Mg + __Mn2O3 --> __MgO + __Mn 3Mg + Mn2O3 --> 3MgO + 2Mn

7. Na + H2O NaOH + H2

2Na + 2H2O 2NaOH + H2

8. H2SO4 + Ca(OH)2 CaSO4 + H2O H2SO4 + Ca(OH)2 CaSO4 +2 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

Synthesis – “putting together”

H2(g) + Cl2(g) ----> 2HCl(g)

C(s) + O2(g) ----> CO2(g)

CaO(s) + H2O(l) ----> Ca(OH)2(s)

Decomposition: AB A + B Decomposition – “breaking apart”

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

Single replacement reactions - When one element displaces another element in a compound

Zn(s) + H2SO4(aq) ----> ZnSO4(aq) + H2(g)

2Al(s) + 3CuCl2(aq) ---> 2AlCl3(aq) + 3Cu(s)

Cl2(g) + KBr(aq) ----> KCl(aq) + Br2(l)

Double Replacement: AB + CD AD + CB Double Replacement reaction – chemical reaction

where two reactant ionic compounds exchange ions to form two new product compounds with the same ions.

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)

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)