F321: Atoms and Reactions

F321: Atoms and Reactions

1. Atomic Structure & Masses

   • Isotopes of the same element have: different masses, the same number of electrons and protons, different number of neutrons
   • Calculate relative atomic mass, decimal percentage multiplied by the isotope mass number
   • Relative masses: Proton = 1, Neutron = 1, electron = 1/2000
   • Relative charge = -1 electron, 1 proton, 0 neutron

2. Definitions:

   • Isotopes:- atoms of an element with different numbers of neutrons and different masses
   • Relative isotopic mass - the mass of an atom of an isotope of an element compared with one 1/12 of the mass of c12
   • Relative atomic mass - the weighted mean mass of an atom of an element compared to 1/12 of the mass of c12
   • Molar Mass - mass per mole of a substabce
   • Empirical formula - simplest whole number ration of atoms of each element present in a compound
   • Molecular formula - the actual number of atoms of each element present in a compound
   • Atomic Number - the number of protons in the nucleus of an atom
   • Mass Number - the number of atoms in the nucleus
   • Ion - a positively of negatively charged atom
   • Relative molecular mass - the weighted mean mass of a molecule compared with 1/12 of the mass of c12
   • Relative formula mass - the weighted mean mass of a formula unit compared to 1/12 the mass of c12
   • Amount of substance - the quantity whose unit is the mole
   • Mole - the amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the c12 isotope
   • Molecule small group of atoms covalently bonded
   • Molar volume - the vol per mole of a gas, units = dm3 mol-1, at room temp and pressure aprox 24
   • Concentration - of a solution is the amount of mil dissolved in 1 dm
   • Stoichiometry - the molar relationship between relative quantities of substances taking part in a reaction
   • Acid - proton donor
   • Base - proton acceptor
   • Alkali - a type of base that dissolves in water to form OH- ions
   • Salt - a chemical compound formed when an h+ from an acid id replaced with a metal ion
   • Oxidation Number - is a measure of the number of electrons that an atom used to bond with atoms of another species
   • Oxidation - loss of electrons or an increase in oxidation number
   • Reduction - gain of electrons or a decrease in oxidation number
   • Redox reaction - a reaction where oxidation and reduction takes place
   • Reducing Agent & Oxidising agent - reducing - a reagent that reduces(adds electrons to) another species. Oxidation - a reagent that oxidises ( takes electrons from) another species

3. Formulas

   • moles=mass/mr
   • Gas volumes
     • vol in (dm) moles=V/24
     • Vol in (cm) moles=v/24000
   • Moles = conc x vol(dm)
   • Moles = conc x vol/1000 (cm)

4. Acids and Bases

   • Acids
     • Sulphuric Acid --> H2SO4
     • Hydrochloric Acid --> HCl
     • Nitric Acid --> HNO3
     • When an acid is added to water it releases H+ ions into the solution
   • Bases
     • Common bases are metal oxides and hydroxides
     • Bases neutralise acids
   • Alkalis
     • Sodium hydroxide --> NaOH
     • Potassium Hydroxide --> KOH
     • Ammonia --> NH3
     • An alkaline is a special base that dissolves in water forming aqueous OH- ions

5. Salts

   • A salt is an ionic compound with the following: positive ion (cation) is usually a metal ion or an ammonium ion. The negative ion (anoin) in a salt is derived from an acid.
   • Salts can be made from: carbonates, bases, alkalis
   • Salts from carbonates: Acid + Carbonate --> Salt + Water + CO2
   • Salt from Bases: Acid + Base --> Salt + Water
   • Salt from Alkalis: Acid + Alkali --> Base + Water
   • Ammonium Salt & Fertilisers
     • Ammonium salts are formed when acids are neutralised by aqueous ammonia
     • NH3 + HNO3 --> NH4NO3

6. Titartions

   • Colour changes
     • Bromothymol Blue
       • Colour in Acid - Yellow
       • End Point - Green
       • Colour in Base - Blue
     • Methyl Orange
       • Colour in acid - Red
       • Colour in Base - Yellow
       • End Point - Orange
     • Phenolphthalein
       • Colour in acid - Colourless
       • End Point - Pale Pink
       • Colour in Base - Pink

7. Oxidation & Reduction

   • Oxidation
     • Oxidation Numbers
       • Uncombined element = O
       • Combined Oxygen = -2
       • Combined Hydrogen = +1
       • Simple Ion = charge on ion
       • Combined Fluorine = -1
       • Chlorine usually = -1
     • Oxidation numbers in chemical names
       • Compound of transition element usually indicate the oxidation number in the name
     • The sum of the overall oxidation numbers must equal the overall charge
   • Reduction
     • non metals tend to be reduced whilst metals tend to be oxidised
     • A reaction in which oxidation and reduction occurs is called a redox reaction
     • TIP - write each oxidation number below each atom and then calculate whether its oxidation or reduction
     • Redox reaction of Acids and metals:- the metal is oxidised, forming positive metal ions, the hydrogen in the acid id reduced, forming the element hydrogen as a gas
   • Oxidation is gain of oxygen - Reduction is the loss of oxygen
   • Oxidation is the loss of electrons - Reduction is the gain of electrons
   • Reduction is a decrease in oxidation number - Oxidation is an increase in oxidation number