balancing equations - skills for life trust · 2018. 2. 6. · balancing equations you can never...

• What are the symbols for the following elements:

1. Sodium

2. Oxygen

3. Chlorine

4. Iron

5. Copper

• What are the formulas for the following compounds:

1. Water

2. Potassium hydroxide

3. Magnesium oxide

4. Potassium iodide

5. Caesium oxide

Balancing Equations

TBAT balance chemical equations

Key facts

In chemical reactions new substances are made.

A reaction can be summarised in a word equation or a symbol equation.

The total mass of reactants is the same as the total mass of products in a reaction

A symbol equation must be balanced as no atoms are created or destroyed.

State Symbols

• (s)

• (l)

• (g)

• (aq)

• E.g.

1. H2

2. O2

3. CO2

4. H2O

5. C

What is wrong with this equation?

• Lithium was added to water in a school lab. Below is the symbol equation for the reaction – or is it?

Li(s)+ H2O(s) LiO(aq) + H2(g)

http://www.youtube.com/watch?v=8ypUVpwgcAA

Balancing equations

You can never change a formula when balancing an equation. You can only put a number in front of a formula.

Lets consider how to show 2 molecules of CO2:

C2O X

CO4 X

C2O2 X

2CO2

Symbol equations

• No atoms are created or destroyed in a chemical reaction.

• There should be the same number of atoms of each type of element each side of the equation.– Magnesium + Oxygen Magnesium oxide

One carbon atom and two oxygen atoms react.

How many atoms are in the product?

C OO

OCO

C + O2 CO2

C OO OCO

How Will Our See-Saw Look?

C + Cl2 CCl4

Cl

C

Cl

Cl Cl

Cl ClC

It’s a Bit Product Heavy

Cl

C

Cl

Cl Cl

C

C + 2Cl2 CCl4

Now everything balances!

C + 2Cl2 CCl4

Cl

C

Cl

Cl Cl

Cl ClC

Cl Cl

How will the see-saw look here?

4O2 + S8 8SO2

S SS

S S

S

S

S

OO

How can we change this?

4O2 + S8 8SO2

S SS

S S

S

S

S

OO S = 1O = 2

S = 8O = 2

S = 8O = 16

8O2 + S8 8SO2

S SS

S S

S

S

S

OO

OO

OO

OO

OOOO

OO

OO

S = 8O = 2S = 8

O = 16

S = 8O = 16

8O2 + S8 8SO2

S SS

S S

S

S

SOO

OO

OO

OO

OO

OO OO

OO

S = 8O = 16

S = 8O = 16

Balance This Equation

Ag + S8 Ag2S

Ag

Ag = 1S = 8 Ag = 2

S = 1

Balance these equations

1. C + O2 CO2

2. H2 + O2 H2O

3. N2 + H2 NH3

4. CH4 + O2 CO2 + H2O

Fe + H2SO4 FeSO4 + H2

Mg + HNO3 Mg(NO3)2 + H2

Zn + HCl ZnCl + H2

When you are done turn these into word equations.

Balance These Equations

Question sheet

Chemistry

What colour is a strong acid on the

pH scale?

What ions are made by acids and

alkalis?

What colour is an alkali in

phenolphthalein?

When you mix an acid and alkali what do you

make?

Calcium carbonate + nitric acid ->

Potassium oxide + hydrochloric acid ->

Sodium hydroxide + sulphuric acid ->

Define soluble and insoluble

What are the formulas of nitric acid and sulphuric

acid?

Chemistry

Chemistry

Soluble in water Insoluble in water

all common sodium, potassium and ammonium salts

all nitrates

most chlorides silver and lead chloride

most sulfates lead, barium and calcium sulfate

sodium, potassium and ammonium carbonates

most carbonates

sodium, potassium and ammonium hydroxides

most hydroxides

Use the table below to name 3 soluble and 3 insoluble compounds

e.g. sodium nitrate lead carbonate

Bingo

Make a 3x3 grid with some of these symbols

Ag

Ar

Au

CH4

CO2

Cu

Fr

H2

H2O

H2SO4

HCl

HNO3

K

Mg

N2

O2

-OH

Pt

S

Sn

Zn