section 9.1 reactions and equations in a chemical reaction… atoms are ____________ (fill in the...
TRANSCRIPT
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