1. CHEMICAL Equations

2. WORD EQUATION Symbolic Equation
Potassium metal oxygen gas  potassium oxide
Reactants are on the left-hand side of the equation
+ sign means “reacts with”
Products are on the right-hand side of the equation
Arrow means produces/yields/ makes
Symbolic Equation
4 K(s) + O2(g)  2 K2O(s)
STATE OF MATTER
Letters indicate the state of each compound.
(aq) = aqueous/dissolved in water
(s) = solid
( l ) = liquid
(g) = gas
COEFFICIENTS
Indicates how many of each molecule there is.
i.e.: there are 4 molecules of K

3. Conservation of Mass - total mass of the products is always equal to the total mass of the reactant

4. Balancing Equations 4 2 K + O2  K2O
Law of conservation of mass says you must have equal number of atoms on the reactant side as there is on the product side.
Compare reactants with products, which atoms are unbalanced????
Note: If there is no number as a coefficient than it is 1
You can only change the coefficients (in front of each substance) and not subscripts behind! 4 2

5. TIPS for Balancing Equations
Balance chemical equations tips
Count all atoms & recount each time
Polyatomic ions (such as SO42–) can often be balanced as a whole group
Balance the H’s 2nd last
Balance O’s Last
Always double-check after you think you are finished!

6. Balancing Equations Li + AlCl3  Al + LiCl 3 3
1 Lithium, 1 Aluminum 3 Chlorine Lithium, 1 Aluminum 1 Chlorine
Recount: 1 Lithium, 1 Aluminum 3 Chlorine Lithium, 1 Aluminum 3 Chlorine
Recount: 3 Lithium, 1 Aluminum 3 Chlorine Lithium, 1 Aluminum 3 Chlorine 3 3

7. CH4(g) + O2 (g)  H2O(aq ) + CO2(g)
Balancing Equations
CH4(g) + O2 (g)  H2O(aq ) + CO2(g) 2 2
1 Carbon, 4 Hydrogen, 2 Oxygen  1 Carbon, 2 Hydrogen, 3 Oxygen
– do O last and H 2nd last.
Recount: 1 Carbon, 4 Hydrogen, 2 Oxygen  1 Carbon, 4 Hydrogen, 4 Oxygen
Recount: 1 Carbon, 4 Hydrogen, 4 Oxygen  1 Carbon, 4 Hydrogen, 4 Oxygen

8. 2 2 H2SO4 + NaF  Na2SO4 + HF Balancing Equations

9. 2 3 2 3 4 12 6 2 7 4 Balance the following: Fe + Br2  FeBr3
Sn(NO2) K3PO4  KNO Sn3(PO4)4
C2H O2  CO H2O 2 3 2 3 4 12 6 2 7 4

10. Turn Word Equations into
Balanced Equations
Example #1:
Word Equation: Solutions of lead (II) nitrate react with potassium iodide to produce solid lead (II) iodide and a solution of potassium nitrate.
Skeleton Equation: Pb(NO3)2(aq) + KI(aq)  PbI2(s) + KNO3(aq)
Balanced Equation: Pb(NO3)2(aq) + 2KI(aq)  PbI2(s) + 2KNO3(aq)
Example #2:
Word Equation: Copper reacts with hydrogen nitrate to produce copper (II) nitrate plus hydrogen.
Skeleton Equation: Cu + H(NO3)  Cu(NO3) H2
Balanced Equation: Cu + 2H(NO3)  Cu(NO3) H2