Module 2 - foundations

• protons: positively charged particles in the nucleus of an atom that has a mass of 1
• neutrons: neutral subatomic particle that has no charge and is found in the nucleus of an atom with a mass of 1
• electrons: negatively charged particles in shells of an atom that have a relative mass of 0.0005
• compound: a substance that contains two or more elements chemically bonded together
• molecule: a group of atoms that are chemically bonded together with either elements or compounds
• mixture: 2 or more elements or compounds that are not chemically bonded together
• ions: atoms or molecules that has a charge due to the loss or gain of electrons
• isotope: an atom of an element with the same number of protons but a different number of neutrons
• Calculation:

  number of neutrons = mass number - atomic number
• relative atomic mass: the average mass of an atom compared to 1/12th the mass of an atom of carbon-12
• Calculation:

  Abundance

  A) percentage abundance

  B) total percentage

  C) mass number

  
• mass spectroscopy: a way of calculating the mass of a sample

  1. inject sample
  2. vapourisation
  3. ionised to become positive ions
  4. travel through a chamber / magnetic field
  5. the time taken to detector is measured
  6. mass is calculated
• Democritus (450BC):

  1. He developed the atomic theory
  2. if something is invisible it's still there
• Dalton (1803):

  • Elements are atoms with different masses
• JJ Thompson (1897):

  1. discovered the negative electron found by using cathode rays
  2. atoms are neutral so something made it positive
• Rutherford (1909):

  1. discovered the positive nucleus
  2. alpha scatter particle experiment
  3. atoms are mostly empty space
  4. discovered the proton
• Bohr (1913):

  1. electrons orbit the nucleus due to electrostatic forces and are in shells
  2. higher frequencies of light have more energy eg./ gamma or Xray
• Schrodinger (1927):

  1. uses probability distribution for the different energy levels to show electrons are within a cloud instead of shells
  2. electrons are within orbitals
• Chadwick (1932):

  1. discovered the neutron within the nucleus
• Moles: the amount of a substance relative to the amount of carbon in 12 grams of carbon-12
• Avogadro's constant: the number of atoms per 1 mol of carbon-12

  1 mol = 6.02 x1023
• Calculation:

  number of entities = moles x  6.02 x 1023
• molar mass: the mass of one mole of a substance in grams
• Calculation:

  Moles

  $moles =$$mass/Mr$
• concentration: the amount of solute in a given volume of solution, measured in mol/dm3
• volume: is a measure of the amount of liquid in dm3
• Calculation:

  concentration

  $conc (moldm^-3) =$$mols/volume (dm^3)$
• converting:

  A) /1000

  B) X1000

  C) metres 3

  
• molar gas volume: the volume per mole of gas molecules at a stated temp and pressure
• RTP = room temp and pressure

  room temp = 20 degrees

  room pressure = 101kPa

  at RTP = 1 mol of gas has a volume of 24dm3
• Calculation:

  gas volume

  $moles =$$volume (dm^3)/ gas volume (dm^3)$
• ideal gas assumptions:

  1. random motion
  2. elastic collision
  3. negligible size/ small size
  4. no intermolecular forces
• Calculation:

  ideal gas

  $pressure(Pa)×volume(m³) =$$mols×gas constant(mol^-1K^-1)×temp(K)$
• lowest temperature:

  absolute zero = 0K (Kelvin)

  0K = -273

  0°C = 273K
• theoretical yield: the maximum amount of product that can be made

  100% isn't possible due to

  - reactions not completing

  - other reactions occurring

  - purifying products losses products

  actual yield < theoretical yield
• Calculation:

  percentage yield

  $percentage yield =$$actual (mol)/theoretical (mol)× 100$
• atom economy: the ratio of the amount of product formed to the amount of reactants used in a chemical reaction

  • efficient processes have high atom economies so they are sustainable
• Calculation:

  Atom economy

  $atom economy =$$desired(Mr)/total(Mr) ×100$
• Empirical formula: The simplest whole number ratio of atoms of each element in a compound

  1. find the mass of each element
  2. calculate the moles
  3. divide by the smallest number
  4. round to a whole number
• aqueous: solid dissolved in water