Section 9.1 REACTIONS

AND

EQUATIONS

In a chemical reaction…

atoms are____________

(fill in the blank)

What are some common reactions in your everyday life?

How can you tell when a chemical reaction has

taken place?

Formation of a ___________________

also known as a ___________________

HOW DO CHEMISTS

REPRESENT CHEMICAL

REACTIONS?

Chemists use ______________ to represent chemical reactions. The starting substances are

__________________What you

end up with are _____________When do you use chemical equations in your own life?

REAL LIFE EXAMPLE: You are going to bake cookies. You know that:

____flour + ____sugar + ____baking powder + ___butter + ___chocolate chips makes ___cookies

This is a _______________EQUATION. What are the product(s)? What are the reactant(s)?

What else do you need to know….

if you already know that you need to bake them at 350 for ½ hour??

You need to know the _________________

______________________ of the ingredients with respect to each other.

In other words, you need a

___________________ ________________ (Remember – cooking is chemistry!!)

HOW MIGHT A CHEMIST USE A

CHEMICAL EQUATION?

You are an EVIRONMENTAL CHEMIST concerned about

GLOBAL WARMING

You are asked to determine how much carbon dioxide will be produced from the amount of methane burned by a factory. The first thing you need is a WORD EQUATION

methane + oxygen yields

carbon dioxide + water

Word equations are clunky and they don’t tell you very much… You can make your equation less clunky if you use

_________________________instead of words.

__ CH4 + __O2

__CO2 + __ H2O

This type of equation is a

____________

equation.

In addition, to give more information in an equation, symbols are used to

represent the _____________________ of the substances, including:

Solids = _______ Aqueous = ______Gases = _______ Liquids = ______

(Aqueous means __________________

_________________________________

__ CH4(g) + __ O2(g)

__ CO2 (g) +__ H2O(l)

This equation still doesn’t have enough information…What else do you need?

What law allows us to balance equations? State this law.

CH4

O2

CO2

H2O

A very important rule in balancing equations: never change the

________________________

For example: ______ cannot be changed to _______

However, the coefficients can be changed in order to balance the equation. Begin by counting the number of

___ Na(s) + ___ Cl2 (g) ___ NaCl (s)

__ Al2O3(s) ___ Al(s)+ ___O2(g)

___ Fe(BrO3)3 → ___ FeBr3 + ___ O2

ANOTHER RULE: If you balance an

equation, and then find that all of the coefficients are divisible by a common number, you must divide them by that number…

2CH4 + 4O2 2CO2+4H2O

WRONG!

CH4 + 2O2 CO2+2H2O

RIGHT!!

Hint #1If a polyatomic ion

appears unchanged on both sides of the

equation, balance it as a unit – not as individual

atoms

Example #1 of Hint #1

__Al(NO3)3 + __LiOH

__LiNO3 + __ Al(OH)3

[ ]

[ ][ ]

[ ]LiOH

Al(NO3)3

[ ]

[ ]

[ ]Al(OH)3

][LiNO3

Example #2 of Hint #1

__(NH4)3PO4 +__ BaSO4

__(NH4)2SO4 +__Ba3(PO4)2

Example #3 of Hint #1:(involves an acid-base reaction)

__ H2SO4 + __KOH ___K2SO4 + __ H2O

Hint #2 for balancing an equation:First, balance an element that only appears

in one reactant and one product (leaving oxygen to last and hydrogen to second last.)

__C3H8 +__O2 __CO2 + __H2O

Example of Hint #2

__C5H12 (g)+__O2(g)

__CO2(g) + __H2O(l)

HINT #3If you balance all of the elements

ansd the polyatomic ions, except for one element, and there’s an odd # of

that element on one side, and an even number on the other side – balance

that element with a fractional number (containing ½) and then

double all of the coefficients

EXAMPLE:__C5H10 + __O2 __CO2 + __H2O

__C6H14 + __O2 __CO2 + __H2O