C4

  • Chemical symbols and formulae

Common Symbols:

Al – Aluminum

B – Boron

S – Sulfur

N – Nitrogen

Hg – Mercury

Ca – Calcium

Ne – Neon

P – Phosphorus

Cu – Copper

He – Helium

Si – Silicon

K – Potassium

I – Iodine

Fe – Iron

Ag – Silver

Na - Sodium

Common Compounds:

NH3 – ammonia

C2H5OH – ethanol

Ca(OH)2 – calcium hydroxide

C6H12O6 – glucose

CO2 – carbon dioxide

H2O – water

HNO3 – nitric acid

Na2CO3 – sodium carbonate

CuSO4 – copper sulphate

H2SO4 – sulfuric acid

HCl – hydrochloric acid

NaOH – sodium hydroxide

Chemical Symbols and Formulae

    • Tricks
      • Metal + OH -> hydroxide
      • xOH -> alcohol
      • CO3 -> carbonate
      • SO4 -> sulphate

Formulae of ionic substances

    • Shows ratio of no. of ions in ionic compound
    • Size of charge on ion → measure of valency or combining power
    • Elements can have two ions with different valencies
      • Can form different compounds
    • Distinguish different ions with Roman numerals
    • Charge of element: oxidation state

Molecular formula

    • Organic compound: one/more carbon atoms covalently bonded to other element atoms
      • Common: hydrogen, oxygen, nitrogen
      • Convention
        • C2H4BrCl
        • First: carbon
        • Second: hydrogen
        • Third: other elements -> alphabetical order
      • Ionic compound
        • Ions: charged particles (atoms or molecules)
          • Cations: atom with positive charge
          • Anion: atom negative charge
        • Monoatomic ion: one atom
        • Polyatomic ion: two or more atoms covalently bonded together

“Cross-over” method

      • Work out formula of compound
      • Swap vacancies. Vacancy of 1 Element after symbol of 2 element: vice versa
      • Aluminium Sulfide
        • Valency is
        • A = 3 and S = 2
        • So the chemical formula is
        • Al2S3
      • Method
      • Write vacancies of each ion
      • Switch numbers
  • Chemical equations
    • Ionic equations
      • Different to chemical equation: only show species taking part in reaction
      • Has spectator ions → not in ionic equation
        • Do not change state
      • ex.
        • Chemical: NaCl(aq) + AgNO3(aq) - AgCl(s) + NaNO3(aq
        • Ionic: Cl-(aq) + Ag+(aq) - AgCl(s)
      • Must balance no. of atoms + same overall charge on each side
  • Relative atomic mass
    • Relative atomic mass (r.a.m (one element))
      • Mass of atoms compared with mass of carbons (12) atom
      • Each element = different
    • R.A.M: larger of two numbers in periodic table
    • Not always whole number
      • Average relative atomic mass
      • All isotopes of each element
    • Relative formula mass (r.f.m (multiple elements))
      • Sum of relative atomic masses of all elements in substance formula
      • Compounds (H2O)
    • Steps
      • Write down word equation
      • Write chemical equation
      • Write balanced equation
      • Work out R.F.M of each compound
      • Put in grams as unit
      • Answer
  • Mole

Mole

    • Avogadro’s constant: 6 x 10^23 atoms, ions or molecules
    • 6 x 10^23 atoms of magnesium = 1 mole of magnesium
    • There are 6 x 10^23 atoms of one element in 1 mole of that element, which is equal to the element’s atomic mass in grams
    • R.A.M/ R.F.M in g = 1 mole (6 x 10^23 atoms)

Calculating Moles

    • R.A.M/ R.F.M in g = 1 mole (6 x 10^23 atoms)
    • Mass (g) = no. of moles x R.A.M/R.F.M (mass of 1 mole)
    • Steps
      • Write 2 things you have from triangle
      • For R.F.M → calculate first
      • Calculate
      • Include units

Moles & Gases

    • Use volume → measure no. of moles in gas
    • 1 mole of gas = 24dm^3 (24 litres): when room temp + pressure (rtp)
    • Volume of gas (dm^3) = no. of moles x 24

Moles & solutions

    • No. of moles = concentration (mol/ dm^3) x volume (dm^3)
      • N=CV
    • Keep units dm^3
      • cm^3 / 1000 = dm^3
    • 1 molar solution: 1 mole of substrate dissolved in water + solution = 1dm^3 (1000cm^3)

Moles & chemical equation

    • balanced equation shows no. of moles in products + reactants
    • ex. 2Mg + O2 → 2MgO
      • 2 moles magnesium
      • 1 mole oxygen
      • 2 moles magnesium oxide
    • Law of conservation of mass
  • Limiting reactant
    • Chemical reaction stops when 1 reactant is used up
      • Limiting reactant
      • Determine amount of product produced
      • Excess reactant: reactant left over
    • Method (ex. How many moles of zinc iodine is produced if 0.5 moles of zinc react with 1 mole of iodine? Calculate the mass.)
      • Ideal set up (balanced equation → gives moles)
        • Zn + I2 → ZnI2
        • 1 mole zinc
        • 1 mole iodine
      • What you really have (moles of reactants)
        • 0.5 moles zinc
        • 1 mole iodine
      • Limiting agent
        • Zinc
      • New molar ratio
        • 0.5Zn + 0.5I2 → 0.5ZnI2
      • Use triangle
        • Mass (g) = 0.5 x 319
        • = 159.5
        • =160g