Chapter 1, experimental chemistry

• What substances sublimes

  1. ammonium chloride
  2. dry ice ( solid carbon dioxide )
  3. solids iodine crystals
  4. naphthalene
• how do you separate a solid-solid mixture

  1. magnetic attraction ( e.g. grey solid iron and yellow solid sulfur )
  2. sublimation ( e.g. solid iodine crystals )
• how to separate insoluble solid-liquid mixture

  e.g. sand in water

  • filtration ( technique)
  • solvent is obtained as filtrate ( water )
  • insoluble solid is obtained as residue ( sand )
• how to separate soluble solid-liquid mixture (obtain solid)

  e.g. salt in water

  • crystallisation ( technique )
  • if solids decomposes on heating ( solid is not thermally stable, e.g. sugar )
  • evaporation to dryness ( technique )
  • if solid does not decompose on heating ( solid is thermally stable, e.g. salt )
• how to separate soluble solid-liquid mixture ( obtain solvent : water )

  e.g. salt and water

  • Simple distillation ( technique )
  • ethanol ( example )
  • which ha a lower boiling point, would distill over first, followed by water
• How to separate liquid-liquid mixture ( immiscible liquids ) e.g. water and oil

  • separating funnel ( technique )
• how to separate liquid-liquid mixture ( miscible liquids)

  e.g. ethanol and water

  • fractional distillation ( technique )
  • serration based on difference in boiling points of liquids ( why )
• how to identify solutes on paper chromatography

  • based on comparison of Rf values ( how )
  • where the spot traveled to / solvent front ( how to calculate Rf)
• how to determine f a substance is pure based on paper chromatography

  • one spot seen on chromatograph = pure substance
• advantage of using paper chromatography

  • amount of sample needed is small
• What does a locating agent do

  Using a locating agent help to react a colourless spot to produce a coloured product to make the spot visible
• gas collection methods

  1. water displacement
  2. downward delivery
  3. upward delivery
• factors of water displacement

  • insoluble to slightly soluble ( solubility of ga in water )
• factors of downward delivery

  • denser than air ( density of air )
• factor of upward delivery

  • less dense than air ( density of gas)
• Gases that are very soluble-soluble in water

  1. Ammonia ( extremely)
  2. hydrogen chloride ( very )
  3. Sulfur dioxide ( very )
  4. chlorine ( soluble )
• gases that are slightly soluble-not soluble

  1. carbon dioxide ( slightly )
  2. oxygen ( barely )
  3. hydrogen ( not soluble )
• how to calculate density of gas

  • relative molecular mass of gas must be higher than 28 ( to be denser than air )
  • calculate Mr of molecule ( how )
  • 78% of air is nitrogen gas, N2 which has a Mr of 28 ( why )
• which gas is acidic

  1. sulfur dioxide
  2. hydrogen dioxide
  3. carbon dioxide
• which gas is alkali

  1. ammonia
• methods for drying gases and what their used for

  1. quicklime ( calcium oxide ) [ dry ammonia ]
  2. fused calcium chloride [ dry anything other than ammonia ]

  
• methods for drying gas and what their used for

  1. Concentrated sulfuric acid [ anything that is acid ]

  
• Property of pure substance

  • a pure substance has a specific melting and/or boiling point under fixed conditions
• time [ SI unit and apparatus ]

  • second (s) [ SI unit ]
  • stopwatch [ apparatus ]
• temperature [ SI unit and apparatus ]

  • kelvin ( K ) [ SI unit ]
  • thermometer
• length [ SI unit and apparatus ]

  • metre ( m ) [ SI unit ]
  • metre rule, measuring tape [ apparatus ]
• Apparatus to measure volume

  1. Pipette
  2. volmetric flask
  3. Measuring cylinder
  4. burette
• how much volume does pipette measure

  10.0 cm3 or 25.0 cm3
• how much volume does volumetric flask

  100cm3 or 250cm3
• how much volume does measuring cylinder measure

  Nearest 0.5cm3
• how much volume does beretta measure

  nearest 0.05cm3
• Identify the parts

  a-conical flask

  b-barrel

  c-plunger

  
• A- beaker

  b- filter paper

  c- residue

  d- filter funnel

  e- conical flask

  f- filtrate

  
• Steps for crystallisation

  1. Stir the solid to dissolve in the solvent
  2. Pour the solution into an evaporating dish
  3. gently heat the solution to evaporate most of the liquid till the solution is saturated
  4. Stop heating the solution before all the solvent has evaporated
  5. cool the solution gradually till the solid appears within the solution
  6. carefully pour the mixture through a funnel lied with filter paper to collect the residue
  7. wash the residue with some cold distilled water to remove impurities
  8. dry it between a few sheets of filter paper
• a- boiling chips

  b- distillation flask

  c- thermometer

  d- condenser

  e- out

  f- in

  g- conical flask

  h - distillate

  
• steps for simple distillation

  1. Fill up the distillation flask halfway
  2. set up the apparatus
  3. Slowly heat the solution keeping an eye on the thermometer
  4. the solution evaporates and enters the condense through the exit sidearm of the distillation flask
  5. the vapour loses heat and condenses back into liquid water
  6. pure water is then collected in the conical flask as the distillate
• A- round bottom flaask

  b- boiling chips

  c- fractionating column

  d- glass beads

  e- thermometer

  f-condenser

  g- out

  h- in

  i- conical flask (reciever)

  
• What is the use of the fractionating column and glass beads

  The fractionating column contains glass beads to provide a larger surface area for the vapour to condense back into a liquid
• explain why the flow of water must be from the bottom to the top

  in order to have an effective and efficient cooling effect to condense a vapour into a liquid, this ensure that the condenser is fully filled
• steps for sublimation

  1. heat the mixture on an evaporating dish with an inverted filter funnel till iodine sublimes
  2. collect the iodine crystals as it deposits on the cool dry surface of the filter funnel.