Chapter 5 - Writing/Balancing Equations

Question 1

Naming Compounds

Answer 1

Rule 1 - Ends in “-ide” contains 2 elements e.g Calcium + Oxygen > calcium oxide

Rule 2 - Ends in “-ate/ite” contains 3 or more elements and always oxygen. calcium + Carbon + Oxygen > Calcium Carbonate

Rule 3 - Element furthest left in table named first

Question 2

Group Charges

Answer 2

Carbonate  CO3     -2
Sulphate     SO4     -2
Nitrate        NO3     -1
Hydroxide     OH     -1
Ammonium NH4    +1

Question 3

Balancing Equations

Numbers

Answer 3

Small numbers - Multiplies element/group immediately before e.g NO3 (Oxygen x 3)

Big Numbers - Multiplies All atoms after It e.g 2NO3 (All atoms multiplied by 2 so 2N’s and 6O’s)

Brackets - Everything inside multiplied e.g Mg(OH)2 means OH x 2

Question 4

More Rules

Answer 4

Law of conservation - No matter is destroyed or created

Atoms of Gaseous Elements are balanced last

Popular method - 1) Determine Formula
2) Once correct add only big number

Question 5

Examples

Answer 5

Unbalanced - Cu + O2 > CuO
Balanced - 2Cu + O2 > 2CuO
2 cu and 2 oxygen atoms on both sides

UnBalanced - Ca + H2O > Ca(OH)2 + H2
Balanced - Ca + 2H2O > Ca(OH)2 + H2
Balanced Because: 1 Ca, 4H, 4O on Both sides

Question 6

Formulas we are expected to Know

Answer 6

Diatomic Gases -

Elements of Group 7, Hydrogen, Oxygen, Nitrogen

Acids:

Sulphuric Acids - H2SO4
Sulphurous Acid - H2SO3
Hydrochloric Acid - HCL
Nitric Acid - HNO3

Question 7

Writing Symbol from Word Equations - Rules

Answer 7

1) Use periodic table to write formula and check its correct
2) Once correct do not change formula
3) Balance equation with only big numbers

E.g: 1)Calcium + Water > Calcium Hydroxide +Hydrogen

2) Ca + H2O > Ca(OH)2 + H2
3) Ca + 2H2O > Ca(OH)2 + H2

Question 8

Writing Ionic Equations

• An Ionic equation is a simplified form of the full equation
• Once Equation is balanced identify soluble compounds (Aq) and split them
• All Halides are soluble except Ag + Pb
• Some Sulphates soluble except with Be, Ca, Pb

Answer 8

Example

Symbol Equation - Mg (s) + H2SO4 (aq) > MgSO4 (aq) + H2 (g)
Split ions: Mg 2H+ SO4- > Mg2+ SO4- H2
Identify Spectator Ions (Ions that dont change) and remove to make ionic equation:
mg + 2H+ > Mg2+ + H2
(S) + (Aq) > (Aq) + (g)