1.3 Chemical Calculations

• Mᵣ


  Abreviation for Molecular Mass
• Aᵣ


  Abreviation for Atomic Mass
• Atomic mass


  The average mass of one atom of the element relative to ¹/₁₂ the mass of an atom of carbon-12
• Formula Mass


  The average mass of a molecule/formula unit relative to ¹/₁₂ the mass of an atom of carbon-12
• Isotopic Mass


  The mass of an atom to an isotope relative to the ¹/₁₂ of the mass of an atom of carbon-12
• Molecular Mass


  Total mass of an empirical formula
• Empirical Formula


  A formula showing the proportions of the elements present in a compound but not the actual numbers or arrangement of atoms.
• Molecular Formula


  A formula showing the numbers and types of atoms in a molecule.
• Molar mass


  The mass of a mole of a substance
• Mole


  6 × 10²³ of something
• Atom economy


  A way to measure the atoms wasted when making a chemical .
• Percent yield


  A measure of the efficiency of a chemical reaction using percentage.
• Theoretical yield


  The amount of product predicted to be made based its reaction formula.
• Mole formula


  n=m/M

  Mole = Mass / Molar mass

  
• No. of particles


  N=nL

  No. particles = Moles * Avogadro number
• Volume of gas formula

  Mole = Volume / Molar Volume
• Boyles Law


  Pressure * volume = Constant

  
• Charles Law


  Volume / Pressure = Constant

  Temperature - Kelvin (K)

  
• Avogadro Principle


  Equal volume of different gases contain the same number of particles
• Gas laws

  
• Ideal gases Calculation

  
• Mass Spectrometer


  Use to measure to a great accuracy , measures the Aᵣ of an element and the Mᵣ of a compound.
• Vapourising


  A sample of the element is placed inside as a vapour, solids provide heating, some substances thermally decompose and can't be used.
• Ionising


  Element is in an evacuated chamber under a vacuum. Bombarded by high energy electrons, this results in electron loss and causing positive ions.
• Ionising example


  E + e⁻ → E⁺ + e⁻ + e⁻

  atom + high energy electron → E⁺ + e⁻ + e⁻
• Acceleration


  Positive ions accelerated by the electrostatic field, ions pass through slits which carry the field
• Deflect


  Different ions are deflected by magnetic fields by different amounts. It depends on:

  Mass of ion - Light ions deflected more the heavier.

  Ion charge - Ions with two or more positive deflected more than one positive ion.
• Detection


  Only ions with the correct with the correct mass. The mass and the relative abundance % are indicated by a peak charge. A vacuum is needed to make sure there are no air particles in the way, to give a clean run to the chamber.
• Vacuum


  Gets rid of air particles or any impurities within the chamber, so the ion has a clean run to the detector, so it doesn't effect the result.