Balancing Chemical Equations IPage 1

WATCH ALL SLIDES

Slide 1 Balancing Chemical Equations

Just follow these steps…….

It’s quite easy really

Slide 2 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

Mg

O

Slide 3 Just count up the atoms on each side

Then start balancing:

1

1

1

2

 The numbers aren’t balanced so then add “BIG” numbers to make up for any shortages

2

2

2

Slide 4 But the numbers still aren’t equal, so add another “BIG” number

2

And adjust totals again

NOW BOTH SIDES HAVE EQUAL NUMBERS OF ATOMS

WE SAY THAT THE EQUATION IS BALANCED!!

2

Slide 5 Try to balance these equations using the same method:

 Na + Cl2  NaCl

 CH4 + O2  CO2 + H2O

 Al + O2  Al2O3

 Li + HNO3  LiNO3 + H2

Slide 6 How did you get on??

 2 Na + Cl2  2 NaCl

 CH4 + 2 O2  CO2 + 2 H2O

 4 Al + 3 O2  2 Al2O3

 2 Li + 2 HNO3  2 LiNO3 + H2

Here are the answers:

HOPE YOU’VE GOT THE IDEA… REMEMBER TO CHECK THAT YOU CAN DO ELECTROLYSIS EQUATIONS TOO

Slide 7 Electrolysis equations ones to check

[a] Cu2+ + e-  Cu

[b] Cl- - e-  Cl2

[c] H+ + e-  H2

[d] Br -  Br2 + e-

Slide 8 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-

Slide 9 Hope that makes things a bit clearer….

Just remember it’s all about balance