Transcript Balancing Chemical Equations - Chemistry Resources for IB

Balancing Chemical Equations
Just follow these steps…….
It’s quite easy really
Firstly you need an equation with the correct “formulae”
in………. You’ll probably be given this in the question
Just like this one
Mg + O2  MgO
Then all you do is list the atoms that are involved
on each side of the arrow
Mg + O2  MgO
Mg
O
Then start balancing:
[1] Just count up the atoms on each side
Mg + O2 
MgO
1
Mg
1
2
O
1
[2] The numbers aren’t balanced so then add “BIG”
numbers to make up for any shortages
Mg + O2  2 MgO
And adjust totals
1
Mg
1
2
2
O
1
2
But the numbers still aren’t equal, so add
another “BIG” number
2 Mg + O2  2 MgO
2
1
Mg
2
2
O
2
And adjust totals again
NOW BOTH SIDES HAVE EQUAL
NUMBERS OF ATOMS
WE SAY THAT THE
EQUATION IS BALANCED!!
Try to balance these equations using the same
method:
[1] Na + Cl2  NaCl
[2] CH4 + O2  CO2 + H2O
[3] Li + HNO3  LiNO3 + H2
[4] Al + O2  Al2O3
How did you get on??
Here are the answers:
[1] 2 Na + Cl2  2 NaCl
[2] CH4 + 2 O2  CO2 + 2 H2O
[3] 2 Li + 2 HNO3  2 LiNO3 + H2
[4] 4 Al + 3 O2  2 Al2O3
HOPE YOU’VE GOT THE IDEA…
REMEMBER TO CHECK THAT
YOU CAN DO ELECTROLYSIS
EQUATIONS TOO
Electrolysis equations ones to check
[a] Cu2+ + e-  Cu
[b] Cl- - e-  Cl2
[c] H+ + e-  H2
[d] Br -  Br2 + e-
The answers are….
Remember to balance the charges on each side of the arrow
[a] Cu2+ + 2 e-  Cu
[b] 2 Cl- - 2 e-  Cl2
[c] 2 H+ + 2 e-  H2
[d] 2 Br -  Br2 + 2 e-
Hope that makes things a bit clearer….
Just remember it’s all about balance