J

Unit 3. Chemical Reactions3.3 How do we balance a chemical reaction?

February 8, 2010

DO NOW:

MR #3 An element that has a low first ionization energy and good conductivity of heat and electricity is classified as a

(1) metal (3) nonmetal(2) metalloid (4) noble gas

AIM: How do we balance chemical reactions in order to obey the law of conservation of mass?

CHOICE LOW IONIZATION ENERGY? GOOD CONDUCTIVITY OF HEAT AND ELECTRICITY?

METAL

NONMETAL

METALLOID

NOBLE GAS

Check the TABLE SLOW

Periodic Trends?YES THINK: copper wires

HIGH NO

SOME HIGH SOME LOW SOME YES SOME NO

These are nonmetals already….don’t waste your time!

HOW DO WE BALANCE EQUATIONS?

Step 1. Check that an equal amount of an element appears in the reactants that does in the products

C(s) + O2(g) → CO2(g)

Element Reactants Products

Step 2. If not equal add coefficients

CO

1 12 2

Step 3. Check that the equation is balanced after you add coefficients.

THIS IS A BALANCEDEQUATION

LET’S TRY SOMEH2(g) + O2(g) → H2O(g)

Element Reactants Products

H

O

2 2

2 1

Not equal so we must add COEFFICIENTS!

x 2

x 2

2

= 4

= 2

x 2 = 4

LET’S TRY SOMEKClO3 KCl + O2

Reactants Products

K

Cl

O

1 1

1 1

3 2x 2 x 3 = 6= 6

2 3

x 2

x 2

= 2

= 2

2

x 2

x 2

= 2

= 2

Complete the Independent Practice

-IP will be collected at the end of class!!!

- WORK ON UNIT 1 in your HOMEWORK PACKET

- UNIT 1 completion will be check on Monday at the beginning of class