Intro to Balancing

7/28/2019 Intro to Balancing

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STARTER

Match the formula on the front of your

booklet with its correct name

You have 3 min!


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H NO3 Zn Cl2H2 SO4 Cu Cl2

Ca (OH)2 Ca CO3Ag Br Na OHAg2 O Ca SO4Cu O Mg O

Ag NO3 H ClNa

2SO

4 Na Cl


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Balancing Equations

Everyone should:

Be able to balance simple equations

that use up to 3 valence electrons

Most people will:

Balance equations using compounds

like

OH-

NO3-

SO4 2-

Some people will:

Be able to balance equations with

unusual compounds not covered in

class


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PENS AWAY!!!

NO WRITING

NO NOTE-TAKING

No doodling! (what??)

Just listening and participating for the next

15 min)


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IMPORTANT

ATOMS CANNOT BE CREATED OR

DESTROYED!


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Hydrogen + chlorine hydrogen chloride

H2 + Cl2 HCl

Remember: Hydrogen and Chlorine are diatomic

+

REACTANTS

2 H atoms

2 Cl atoms

PRODUCTS

1 H atom

1 Cl atom

This is impossible as it implies that atoms

have been destroyed.


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What do we do?

We need to make the number of atoms equal on both

sides of the equation, in order to get the equation to

BALANCE.


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What do we do?

We need to make the number of atoms equal on both

sides of the equation, in order to get the equation to

BALANCE.

Equation is now balanced, as there are the same

number hydrogen atoms (2) and the same number of

chlorine atoms (2) on the products and reactant side.


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Firstly you need an equation with the correct formulae in. Youll

probably be given this in the question

Just like this one

Mg + O2 MgO

Mg

O

Then all you do is list the atoms that are involved on each

side of the arrow

Mg + O2 MgO


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[1] Just count up the atoms on each side

Then start balancing:

Mg + O2 MgOMg

O

1

1

1

2

[2] The numbers arent balanced so then add BIG numbers to

make up for any shortages

And adjust totals

Mg + O2 MgOMg

O

1

1

1

2

2

2

2


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Mg + O2 MgOMg

O

1

2

2

2

2

But the numbers still arent 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


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GROUP ACTIVITY: Try to balance theseequations using the same method

You have 5 min!

[1] Na + Cl2 NaCl

[2] CH4 + O2 CO2 + H2O

[4] Al + O2 Al2O3

[3] Li + HNO3 LiNO3 + H2

Why didnt

anyone tell me

it was so easy

to balance

equations???!!!


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How did you get on??

[1] 2 Na + Cl22 NaCl

[2] CH4 + 2 O2 CO2 + 2 H2O

[4] 4 Al + 3 O22 Al2O3

[3] 2 Li + 2 HNO32 LiNO3 + H2

Here are the answers:


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But how do I show this in an

exam?

Yep but this one isnt:

2 H on left

2 Cl on left

---

1 H on right

1 Cl on right

Note to self:I must NEVER EVERchange the formula!

So I have twice as many atoms on

reactants side than the products side.

To balance this I need to double the number

of atoms on the products side

2


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ExamplesIts best to

balance using

whole

numbers

22

3 22

24

22


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Your tasks:

Try the Balancing Equations questions in

your booklet

Following with the more challenging

extension questions on the back of your

booklet

Finish up with a game of Learn the

Formula!


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Ticket to exit..

Balance the equation on your Post-It

correctly

Stick it on the board under the Learning

outcome you feel you achieved today


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Today, I feel I have achievedEveryone should:

Be able to balance simple equations that use up to 3

valence electrons

Most people will: Balance equations using compounds like

OH-

NO3-

SO4 2-

Some people will:

Be able to balance equations with unusual compounds

not covered in class


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Lets act it out! 1 volunteer to be a calciumwrite the symbol on your

sticker

2 volunteers to be chlorine write the symbol on your

sticker

Can you arrange yourselves to make a compound?

What is your formula? What kind of bonds are these?

Now we need to show the equation for this reaction!

Whats missing?

Another 3 volunteers please! Write on your stickers

How does chlorine exist naturally? How will you show

this?

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Intro to Balancing