Chemistry topic 3-formulae,equations,amounts of substance

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Balancing equations

Equations should show:
1. Molecular formula of reactants and products
2. Their state symbols -(s)solid,(l) liquid,(g) gas,(aq) aqueous (in solution)
3. The number of reacting particles
It should be balanced because:
>the law of conservation of mass-matter can neither be created or destroyed.
>so the total mass of products=total mass of reactants
>there is the same amount of atoms on both side but arranged in a different way.
1. Check if equation is balanced by counting atoms on each side
2. If it is not balanced start with balancing the metals.
3. Balance other atoms that are not O or H
4.balance O or H atoms

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Solubility rules

Substances and their solubility:

Sodium,potassium and ammonium salts- all soluble
All nitrates- soluble
Most ethanoates- soluble
Most chlorides,bromides iodides - soluble except for silver chloride and lead chloride,silver bromide,silver iodide,lead bromide and lead iodide
Most sulphates- soluble except barium sulphate ,lead sulphate,and calcium sulphate
Carbonates - insoluble except sodium carbonate,potassium carbonate,ammonium carbonate
Hydroxides - insoluble except sodium hydroxide,potassium hydroxide, and ammonium hydroxide

  • neutralisation- acid +metal hydroxide=salt+water  
  • acid +metal oxide=salt +water
  • acid +metal carbonate=carbon dioxide+water+salt
  • acid+metal=hydrogen +salt
  • precipitate reactions- 2 soluble salts react to form an insoluble salt(precipitate) and a soluble salt.
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Ionic equations


  • 1.Write full molecular equation and balance it and state symbols
  • 2.Write total ionic equation by seperating the ions for dissolved substances
  • 3.For all solids,liquids,and gases write full molecular formula.
  • dilute acids=aq concentrated=l
  • 4.Cross out spectator ions-i.e. thos that have remained the same on both sides of the equation.
  • 5.write out the net ionic equation by leaving out spectator ions.
  • if the physical state of an ion has changed it is a species ion as it has taken part in the bond forming process.
  • In a neutralisation reaction the net ionic equation is:H+(aq)+OH-(aq)>H2O(l)


  • 1.HCL(aq)+NaOH(aq)>NaCL(aq)+H2O(l)
  • 2.H+(aq)+Cl-(aq)+Na+(aq)+OH-(aq)>Na+(aq)+Cl-(aq)+H2O(l)
  • 3.H+(aq)+Cl-(aq)+Na+(aq)+OH-(aq)>Na+(aq)+Cl-(aq)+H2O(l)
  • 4.H+(aq)+OH-(aq)>H2O(l)
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Compound ion charges+formula


Ammonium=NH4(+1)    Carbonate=CO3(-2)     Hydroxide=OH(-1)   Nitrate=NO3(-1)

Nitrite=NO2(-1)             Sulphate=SO4(-2)      Sulphite=SO3(-2)     Chlorate(I)=ClO(-1)

Chlorate(V)=ClO3(-1)    Vandate(V)=VO3(-1)   Manganate(VII)=MnO4(-1)

Chromate(VII)=CrO4(-2) Dichromate=Cr2O7(-2)  Phosphate=PO4(3-)   Ammonia=NH3(-1)


Sulfuric acid=H2SO4    Nitric acid=HNO3  Hydrochloric acid=HCL  Phosphoric acid=H3PO4

Carbonic acid=H2CO3

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The mole

Relative atomic mass:

  • Has no unit
  • relative atomic mass,molecular mass,and formula mass have no units.


  • 1 mol of hydrogen atom has a mass of 1 gram
  • 1 mol of hydrogen molecule has a mass 2 grams
  • 1 mol of sodium chloride has a mass of 58.5grams

Molar mass:example

  • Calculate the molar mass of sulfuric acid H2SO4
  • 2 atoms of H each of mass 1=2x1=2gmol-1
  • 1 atom of S each of mass 32.1=32.1x1=32.1gmol-1
  • 4 atoms of O mass 16=4x16=64gmol-1
  • Total mass=98.1gmol-1
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