Formulae, equations and amounts of substances (1.1)

Foundations of Chemistry
1. Atoms
  1. A greek word meaning indivisable
  2. Structure
    1. Composes of elctron shells and a nucleus
      1. Nucleus contains protons with a + charge, and neutrons with no charge
      2. Elctron shell contain elctrons which have no charge
  3. Atoms of a element consist of the same amount of protons
    1. An element cannot be broken down chemicallly into simpler substances
2. Isotopes
  1. Atoms with the same atomic No. but different No. of neutrons are known as isotopes
    1. The varying No. of neutrons makes the mass of the atoms also vary
    2. Isotopes of a element have smae chemical propertise but different masses
      1. This can make some isotopes radioactive
Formulea and equations
1. Holding atoms together
  1. Ionic bonding
    1. Between non-metals and metals
    2. Atoms lose or gain electrons to gain stable, full outer shells
      1. Metal atoms lose elctrons
      2. Non-metals gain electrons
    3. Strong fources of atraction (ionic bonds) hold opositly charged ions together in giant ionic latice structures
  2. Covalent bonding
    1. Only between non-metals
    2. Atoms share elctrons and this is what holds them together, large covalent latice structure
2. Ionic half equations
  1. You only have to spli up molocules into the seperate ions if they are in an aqueose state in the reaction
  2. Shows exactly whats happening in an equation
3. Molecular equation
  1. Gives a complete description of all reactants
Size/wheight of atoms
1. Relative atomic mass (RAM)
  1. Is a relative scale compared to the mass of a single standard atom of carbon-12
    1. represented by the symbol Ar
  2. Defined as the average mas of a elements isotopes compared with the mass of an atom of carbon-12
2. Mixtures of isotopes
  1. The RAM of every element is an average which reflects the mix of isotopes abd their differing masses within the elemnt
  2. Most elements have one major isotope and small proportions of others
Moles
1. Defined as the amount of substance that contains as many particles (atoms, ions or molecules) as there are atoms in exactly 12g of carbon 12
  1. moles is abreviated to mol
  2. No. moles = mass(g) / molar mass (gmol-1)
    1. Molar mass is just a numerical value of RAM
      1. Tells you the No. of grams of that substance that is needed to make up one mole of that substance
    2. You can 'x' the moles of an element by the avagadro constant to find out the amount of atoms in a cirtain mass
      1. Avagadro constant = 6.02*10**23
2. Using moles
  1. Relative molecular mass (Mr) is the mass of a molecule
  2. The realative formulae mass is used for the mass of ionic compunds
  3. Molar volume
    1. one mole of any gas must ocupy the same volume under the same conditions
      1. This is one of the major implications of avagardros law
      2. Standard conditions are 1 atmosphere (atm) and 298k or 25 degrees celcius
      3. Gases ocupie a volume of 24dm**3
Calculating formulae using moles
1. Empirical formula
  1. This is the simplest ratio that the atoms of a compound can be in
  2. The formula of a compound gives the ratio of different atoms present
2. Molecular formula
  1. Tells you how many atoms of the elments in one mole of a compund are bound together
    1. The empirical formula dose not tell you this
  2. Sometimes the empirical and molecular formula can be the same
  3. Giant structures of atoms nd ions are described by their epirical fromula not molecular
Measuring concentration
1. Moles in solution
  1. A solute is a solid, liquid or gas dissolved in a solvent
  2. Concentration is measured in moles per cubic decimeter (mol dm**3)
    1. i decimeter is equivilent to 1000cm cubed
  3. Concentration (molarity) = moles of solute / volume of solution (dm**3)
2. More units of concentration
  1. % by mass
    1. For use as a quick comparison
    2. % by mass = mass of solute / mass of solution * 100
  2. % by volume
    1. For when you have a mixture of two liquids or two gases
    2. % by volume = volume of one component / Total volume * 100
  3. Parts per million (PPM)
    1. Usefull for when there is very low concentrations involved
    2. Concentration = Mass of component / mass of solution * 1000000
Yeilds and atom economy
1. The yeild of a reaction
  1. This is the % of a product that you recieve from the reaction between two reactants
    1. If the smae mass of reactants reacts to form the same mass of products, then the yeild from the reaction is said to be 100%
    2. This cannot always be achieved and is very rare in most cases, usually due to cirtain factors
      1. The reactants may not be pure
      2. not all reactants will be used up because it is an equilibrrium reaction
      3. Products may be left behind on apparatus
      4. There is always a degree of human error
2. Atom economy
  1. Developed by Professor Barry Trost
  2. His idea was that it was not the overall yield, but the No. of reacting atoms that ended up in product that mattered
  3. Atom Econ (%) = Mass of desired atoms in product / Total mass of atoms * 100
  4. Have to use Relative.F.M

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Formulae, equations and amounts of substances (1.1)

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	Created by josh bart about 10 years ago