IIIIIIIVV II. Balancing Equations (p ) Ch. 8 – Chemical Reactions

A. Balancing Steps 1.Write the unbalanced equation. 2.Count atoms on each side. 3.Add coefficients to make #s equal. Coefficient subscript = # of atoms 4.Reduce coefficients to lowest possible ratio, if necessary. 5.Double check atom balance!!!

B. Helpful Tips n Balance one element at a time. n Update ALL atom counts after adding a coefficient. n If an element appears more than once per side, balance it last. n Balance polyatomic ions as single units. 1 SO 4 instead of 1 S and 4 O

Why is there a 2 after the oxygen? __________________ What are all the diatomic elements? _________________ Oxygen is diatomic Br, I, N, Cl, H, O, F

Reactants Products Yields SubscriptCoefficient

Counting Atoms 1) H 3 PO 4 2) 3NaOH 3) 2K 2 C 2 H 3 O 2 4) Mg 3 (PO 4 ) 2 H – 3 PO 4 – 1 Na – 3 OH – 3 K – 2 C 2 H 3 O 2 – 2 Mg – 3 PO 4 – 2

More Counting Atoms 1) 3Al(NO 3 ) 3 2) 3Al 2 (SO 4 ) 3 3) 2Ca(OH) 2 4) 3NH 4 NO 3 Al – 3 NO 3 – 9 Al – 6 SO 4 – 9 Ca – 2 OH – 4 NH 4 – 3 NO 3 – 3

Balanced or not? n H 2 + O 2 H 2 O n CH 4 + O 2 CO 2 + H 2 O n Mg + O 2 MgO

How to Balance n All the atoms on the reactants side must equal all the atoms on the products side n First, you need to count all the atoms H 2 + O 2 H 2 O H O

How to Balance n Are they equal? n Add coefficients to change the number of atoms H 2 + O 2 H 2 O H O Balanced!! Good job Balanced!! Good job

Al + CuCl 2 Cu + AlCl 3 Al Cu Cl C. Balancing Example Aluminum and copper(II) chloride react to form copper and aluminum chloride

Practice… Sn +HF SnF 2 + H 2 Cu+ AgNO 3 Cu(NO 3 ) 2 +Ag

Now You Try! WO 3 +H 2 W +H 2 O Fe+O 2 Fe 2 O 3 SiO 2 +C SiC+CO