c8

• what does pure mean


  a substance that only contains one type of element or compound
• what does impure mean

  it has different substances mixed with it
• whats a formulation


  a mixture made of definitive proportions according to a formula - it is also made to do something specific
• what do impurities do to the melting point

  decreases it
• what do impurities do tot eh boiling point

  increase it
• what is the boiling point and melting point like for a pure substance


  sharp - eg 27 degrees - 28 degress
• whats the boiling point and melting point like for an in pure substance

  ranged - eg 27 degrees - 33 degrees - this is because there are multiple different substances in there which each have different melting and boiling points
• whats chromatography


  technique which separates inks and dyes according to the size of the particle
• in chromatography where are the smaller particles compared to the larger particles

  smaller particles move further up as the larger particles are heavier
• what is the Rf value always between

  0-1
• how do you calculate Rf value

  Rf value = distance travelled by substance (the spot) / distance travelled by solvent
• if a substance is more soluble how will it move up the paper

  faster
• if t a single spot is produced during chromatography what does it mean about the substance being tested

  it's pure
• if a substance is less soluble, how will it move up the paper

  slower
• if multiple spots are produced during chromatography, what does it suggest about the substance

  its impure
• how do you test for hydrogen

  you will hear a squeaky pop when a burning splint is held over the open end of a test tube containing hydrogen
• how do you test for oxygen

  if you put a glowing splint inside a test tube containing oxygen, the oxygen will relight it
• how do you test for carbon dioxide


  when carbon oxide is bubbled through limewater, the limewater will turn cloudy
• how do you test for chlorine


  dip damp litmus paper into a test tube of the gas and see if it bleaches and turns white from blue - this shows it is chlorine
• if NaOH is added to an unknown solution at it turns into a white precipitate and then more NaOH is added and it turns colourless, what is the unknown

  Al3+
• if NaOH is added to an unknown solution and it forms a white precipitate and after more NaOH being added it stays white, what is the unknown

  either Mg2+ or Ca2+
• if NaOH is added to an unknown solution and it turns blue, what is the unknown

  Cu2+
• if NaOH has been added to an unknown solution and it turns red/brown, what is the unknown

  Fe3+
• if NaOH has been added to an unknown solution and it tuns green, what is the unknown

  Fe2+
• what is the paper referred to in chromatography

  the stationary phase
• what is the term for the line drawn at the bottom of a chromatography paper


  base line
• what is emission spectroscopy


  technique used to analyse the identity and concentration of a substance
• how do you test for halides

  1) add dilute nitric acid

  2) add silver nitrate

  3) chloride ion = white precipitate

  bromide ion = cream precipitate

  iodine ion = yellow precipitate
• how do you test for carbonates

  1) add HCl to carbonate

  2) bubble the gas produced through limewater

  3) positive result = limewater goes cloudy as a white precipitate is formed
• how do you test for sulfates

  1) add dilute HCl

  2) add barium chloride solution

  3) positive result = white precipitate is formed
• what colour flame do lithium compounds produce

  crimson red flame
• what colour flame do sodium compounds produce

  yellow flame
• what colour flame do potassium compounds produce

  lilac flame
• what colour flame do calcium compounds produce

  orange / red flame
• what colour flame do copper compounds produce

  green flame
• what are instrumental methods


  they are accurate, sensitive and rapid methods which are useful when the amount of sample is very small
• describe flame emission spectroscopy

  1) spectroscope measures the exact wavelength of the light emitted by a metal ion

  2) that allows for definite identification - sometimes colours are difficult to distinguish.
• how are concentrations found in flame emission spectroscopy


  by measuring the intensity of light emitted. The more intense light, the greater the concentration of the metal ion in a solution.
• what are cations


  positive ions
• what are anions


  negative ions