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.
Method:
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

Method:

  • 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)

Example:

  • 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

Compounds:

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)

Acids:

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.

Mole(mol):example

  • 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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