Chem paper 2

• What are the 2 characteristics of dynamic equilibrium?

  - constant amount of reactants and products

  - rate of forward reaction = rate of backward reaction and happen at the same time
• what happens to the position of equilibrium if we increase or decrease the pressure?

  increase: the POE moves in the direction of fewer moles of gas

  decrease: POE moves in direction of more moles of gas
• what happens to the position of equilibrium if we increase or decrease the temperature?

  increase: POE moves to endothermic direction

  decrease: POE moves to exothermic
• What is the oxidising agent for chemical oxidation of alcohols?

  potassium dichromate, sulfuric acid
• what colour does ethanol turn during chemical oxidation?


  orange to green
• how to make ethanol via fermentation?

  - sugar solution -> ethanol solution + CO2

  - in 30-40°C with no oxygen (otherwise yeast will respire and produce water and CO2 instead of ethanol)

  - sugarcane is used (renewable resource)

  - ethanol produced is not pure

  - slow reaction

  - low energy inputs, used in wine and beer
• how to make ethanol via hydration of ethene?


  - ethene + water -> ethanol

  - 300°C & 60-70atm

  - ethene comes from crude oil (non-renewable and cheap)

  - ethanol is 100% pure. catalyst: concentrated phosphoric acid

  - fast rate of reaction

  - high energy inputs, used in fuels and solvents
• what are the steps making esters?

  1. measure out 5cm3 of alcohol

  2. measure out 5cm3 of carboxylic acid

  3. place into a beaker of warm water (60-70°C)

  4. add concentrated H2SO4 catalyst and mix alcohol and acid

  5. add sodium carbonate solution to remove H2SO4. Smell.

  
  

  FYI this is a condensation reaction
• What are the key characteristics of addition polymers?

  - Only need one type of monomer

  - Monomers are based on ethene

  - One product made, i.e., the polymer

  e.g. polyethene, polypropene
• What are the key characteristics of condensation polymers?

  - two different monomers

  - monomers and diols and dicarboxylic acid

  - two products made: polymer and water

  e.g. polyester, PET, nylon
• What are the steps for making insoluble salts?

  1. Mix together soluble salt solutions and a precipitate will form

  2. Filter to collect insoluble salt

  3. Wash with water to remove unreacted salt solution

  4. Dry insoluble salt with paper towel
• What are the rules for solubility?


  - All group 1 compounds, ammonium compounds and nitrates are soluble

  - Most chlorides are soluble except: silver chloride, lead chloride

  - Most sulfates are soluble except: silver, lead, barium, calcium sulfates

  - Most carbonates and hydroxides are insoluble except (see bullet 1)
• What is the test for chloride ions?

  Add dilute nitric acid and aqueous silver nitrate and a white precipitate (a.k.a. Silver chloride) will form
• What is the test for ammonium ions?

  Add aqueous sodium hydroxide and warm mixture.

  Gas evolved that turns litmus paper blue and smells strongly of ammonia, hence alkaline.
• Describe flame test colours for lithium, sodium, potassium and calcium.

  Lithium - deep red

  Sodium - golden yellow

  Potassium - lilac

  Calcium - brick red
• What is the chemical test for water?

  Add liquid to anhydrous copper II sulfate which turns white to blue if liquid is water