chemical analysis

• what is a pure substance

  single element or compound not mixed with any other substances
• what do pure elements melt or boil at

  specific temperatures
• what is a pure substance in every day language

  substance that has nothing added to it ie pure milk
• how can you test the purity of a sample

  measure its melting or boiling point and compare with melting or boiling point in a data book
• what do impurities in sample do to the melting and boiling point

  lower melting point and increase melting range
• what do impurities in the sample do the the boiling point

  increase boiling point and cause sample boil at range of temperatures
• what does it mean if the melting point or boiling point is closer to the actual melting point or boiling point

  purer sample is
• what are formulations

  mixture that has been designed for a useful product
• in a formulation how are the components mixed

  in carefully measured quantities so product has required properties
• what are examples of formulations

  fuels, cleaning agents, paints, medicines, alloys, fertilisers, food
• why are formulations important in the pharmaceutical industry

  able alter formulation of pill. so drug delivered to right part of body at right concentration and is consumable and has long shelf life
• how can you tell the product is a formulation

  see information about its composition on packaging. see ratio or percentage of each component
• what does the information packaging also allow you to see

  choose formulation with right composition for particular use
• what a chromatography be used to do

  separate mixtures and give information to help identify substances
• what are the mobile and stationary phase in chromatography

  mobile phase is where molecules can move ie liquid or gas. stationary phase where molecules can't move ie solid or thick liquid
• what do the substances in chromatography constantly move between and what does it create

  mobile and stationary phases ands equilibrium formed between two phases
• what does the mobile phase move through

  stationary phase and anything dissolved moves with it
• what does how fast a chemical moves depend on

  how it is distributed between two phases(whether it spends more time in mobile or stationary phase)
• what happens for the chemical to move further

  if spend more time in mobile phase than stationary phase
• when do components in a mixture normally separate

  stationary phase if components spend different amount of time in mobile phase
• how many spots does a pure substance form

  one spot bc only one substance in sample
• what is the stationary phase in paper chromatography

  chromatography paper ie filter paper
• what is the mobile phase in paper chromatography

  solvent ie ethanol or water
• what does the amount of time the molecules in each phase depend on

  how soluble they are in the solvent. how attracted they are to the paper
• what conditions need to be in place for molecules to travel further up the paper

  molecules with higher solubility in solvent and less attracted to paper. so spend more time mobile phase
• what is the result of chromatography analysis called

  chromatogram
• what is the Rf value

  ratio between distance travelled by dissolved substance and distance travelled by solvent
• formula for Rf value

  distance travelled from baseline spot divided by distance travelled by solvent
• how to see if a certain substance is present In chromatography

  run pure sample of substance alongside unknown mixture. if Rf values of spot and reference match then substance may be present
• what happens if you change the solvent

  Rf value changes
• how do you know that the reference compound is definitely present in the mixture

  if Rf value of compound match Rf value of one of spots in mixture of all solvents
• what happens if Rf value only match one in some solvents

  compounds isn't present in mixture
• how do you test if substance contains carbonates

  put same in test tube. add coupled drops of dilute acid. connect test tube to test tube of limewater. bubble carbon dioxide through limewater and limewater turn cloudy when carbon dioxide present
• how do you test for sulfates

  add dilute hydrochloric acid. then add few drops barium chloride solution. if sulphate ions present white precipitate of barium sulphate forms
• how you test for a halide

  add drops of nitric acid. then add few drops silver nitrate solution
• in test for halides with nitric acid and silver nitrate what does chloride give

  chloride gives white precipitate of silver chloride
• in test for halides with nitric acid and silver nitrate what does bromide give

  bromide give cream precipitate of silver bromide
• in test for halides with nitric acid and silver nitrate what does iodide give

  iodide give yellow precipitate of silver iodide
• what do flame tests do

  identify metal ions
• what colour do lithium ions burn with

  crimson flame