OCR Chemistry - F321 - Module 1

OCR Chemistry - F321 - Module 1

1. The Atom

   • History
     • This is the history of the path to find out what was in an atom and what its structure was. (Unlikely to show up in test)
     • Greeks
       • First idea of the atom. Particles that couldn't be split further.
     • John Dalton
       • They were tiny, spherical and element atoms could be grouped.
     • Joseph John (JJ) Thompson
       • Used cathode rays to discover charges. Came up with the plumb pudding model.
       • • Negatively charged in a 'sea' of positive charges. Small mass
     • Ernest Rutherford
       • Their gold leaf experiment involved firing alpha particles at a thin sheet of gold (only a few atoms thick) He concluded that: The charges must balance Positive centre, negative orbitals. Mainly empty space.
       • • This is what he discovered: Most went through unaffected. Some were deflected sideways. Few were sent backwards.
         • This means that: Most of an atom is empty space due to most of the alpha particles passing through unaffected. The positive charge has to be small and dense to allow the positive alpha particles through the atom, so the surrounding of the atom is negative.
     • Nelis Bohr
       • Orbitals follow a path in 'shells'
     • Henry Mosday
       • There is a link between x-ray frequency and element atomic number
     • Louis de Broglie
       • Atoms behave as particles and waves.
     • James Chadwick
       • High energy alpha particles shot at light elements gave off a new radiation, which lead to the discovery of neutrons.
   • Structure
     • Electron
       • Mass = 1/2000 Charge = -1 Found surrounding the nucleus 
     • Proton
       • Mass = 1 Charge = +1 Found in the nucleus
     • Neutron
       • Mass = 1 Charge = 0 Found in the nucleus.
     • Nucleus
       • Tiny in comparison to the total volume of an atom
     • Reading the structure
       • You will often work with specific elements from the periodic table, this is what you would be given from the table.
       • • Z = element  B = Number of protons A = Total mass
         • Given this, this means....
           • From the periodic table, we can calculate more then just what it gives us.
           • • Calculations: Neutrons = Mass - protons  Electrons = protons - charge (If charge is negative, minus a minus number means to add Charge = electrons - protons
   • Important definitions
     • Masses
       • Relative isotopic
         • The mass of an atom of an isotope isotope compared to 12th of a mole of carbon 12
       • Relative atomic
         • The weighted mean mass of an atom of an element compared to 1/12th of the mass of an atom of carbon 12
       • Relative molecular
         • The weighted mean mass of a molecule compared to 1/12th of the mass of an atom of carbon-12 
       • Relative formular
         • The weighted mean mass of a formula unit compared to 1/12th of the mass of an atom of carbon-12
       • Molar mass
         • The mass per mole of substance
   • Ions
     • A positively or negatively charged atom or covenantly bonded group of ions
   • Isotopes
     • Isotopes
       • Atoms of the same element/atomic number/number of protons but with different number of neutrons/masses
     • Isotopes of the same element have similar/the same chemical properties as the number of electrons in the outer shell are the same/same electron structure or configuration

2. A mole

   • The amount of any substance containing as many particles as there are carbon atoms in exactle 12g of carbon-12
   • Equations
     • If a volume is given in cm^3, remember to either x or / by 1000
     • Gasses
       • Molar volume is the volume per mole of gas. at room temperature and pressure, it is roughly 24 dm^3
       • Avogadro constant
         • The number of atoms in 1 mole of carbon 12 (6.02 * 10^23 mol)
     • Titration
       • Standard solution: A solution of known concentration  Stoichiometry: the molar relationship between relative quantities of substances taking place in a reaction.
       • Methyl orange, red in acid, yellow in base, orange end point 
       • • Molarity = (x by 1000 if in cm^3)
     • Mass
     • Concentration
       • Definition: The amount of solute in mol, dissolved per dm^3 of solution.
     • Ratios
       • • 1 mole of Ca is bonded with 2 moles of OH (1:2 ratio)
         • If moles of Ca(s) is 0.00131 is reactants and Ca(OH)2 is a product, there will still be 0.00131 moles of Ca (assuming the ratios are the same) and 2 moles of OH bonded to it (0.00131 x 2 = 0.00262 mol of OH) 
     • Number of molecules
       • Multiply moles by avogadro constant, 6.02x10^23

3. Formulae

   • Empirical
     • The simplest whole number ratio of atoms of each element in a compound
     • From mass
     • From percentage composition
   • Molecular
     • The actual number of atoms of each element in a molecule.
     • A molecule
       • A molecule is a small group of atoms held together by covalent bonds
   • Relative atomic mass
     • This is to calculated the mean mass of an atom (from all of the atoms isotopes)
     • From percentage composition

4. H+ / OH-

   • Acid
     • A species that is a proton donor
     • When is reacts with water: HCl + (aq) = H+ + Cl- 
     • Examples
       • HCl, HNO3, H2SO4
   • Bases
     • A species that is a proton acceptor  
     • Examples
       • MgO, CuO - metal oxides  NaOH, Mg(OH)2 - metal hydroxides
   • Alkali
     • A type of base that dissolves in water froming OH- ions
     • NH3 + H2O (Equilibrium) NH4+ + OH-
     • Examples
       • NH3, NaOH, KOH

5. Water of crystallisation

   • Hydrated - with water Anhydrous - without water  Water molecules take form an essential part of the crystalline structure of a compound. 
   • • This is what a hydrated crystal looks like, it is called dot formula
   • Equations
     • A way to calculate the mass of water in a hydrated salt.

6. Redox/Oxidation/Reduction

   • Oxidation = loss of electrons  Reduction = gain of electrons
   • Oxidation number rules
     • Elements = 0 hydrogen = +1 exept in peroxides where its +2 Oxygen = -2 Roman numerals gives the elements ion/oxidation number 
     • Oxyanions NO2
   • Agents
     • A reducing agent is what adds electrons to another species  An oxidising agent is what takes electrons from another species. If something in a reaction is reduced, it is an oxidising agent and visa versa.
   • If an element has a roman numeral in the name e.g. Chloric(V) acid, that number represents the oxidation number of that element

7. Salts

   • Salt
     • A chemical compound formed from an acid where the H+ has been replaced by a metal ion (or any other positive ion)
     • A salt is an ionic compound with a cation and anion Cation = positively charged  Anion = negatively charged
   • From carbonates
     • 2HCl(aq) + CaCO3(s) -----> CaCl2 + H2O + CO2
   • From bases
     • 2HCl(aq) + CaO(s) ----> CaCl2(aq) + H2O(l)
   • From alkalis
     • HCl(aq) + NaOH ----> NaCl(aq) + H2O(l)
     • Ammonia
       • NH3(aq) + HNO3(aq) ----> NH4NO3(aq)
   • From acids
     • H2SO4 = Na2SO4
   • From metals
     • These are redox reactions

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