Topic 5 separate chem

• atom economy

  The atom economy of a reaction is a measure of the amount of starting materials that end up as useful products. It is important for sustainable development and for economic reasons to use reactions with high atom economy.
• actual yield


  the amount of product obtained from a chemical reaction
• theoretical yield


  the maximum mass of product that can be formed from a reactant (if all reactants are turned into products)
• percentage yield compares...


  actual and theoretical yield
• how do you find the percentage yield?

  actual yield/theoretical yield x 100
• 100% yield means that...


  you got all the product you expected to get
• What are the main reasons why we don't get 100% yield?

  -> reaction may be incomplete (reached equilibrium, not left long enough, all reactants not reacted)

  -> Some product is lost

  -> There may be unwanted side reactions (to form a different product)
• The higher the percentage yield...


  the more useful a reaction is because less raw materials are needed to make the same amount of product, so there is less waste and more profit
• Atom economy is...


  the percentage of the mass of reactants that are converted into useful products
• how do you find atom economy?

  Mr of useful product / sum of Mr of all reactants X 100
• How can atom economy be improved?

  Find a use for the waste products
• What does 100% atom economy mean?

  all the atoms in the reactants have been turned into the desired (useful) product
• When deciding on a reaction pathway, what other factors need to be considered?

  energy consumption, raw materials, conditions needed to produce a high yield if the reaction reaches equilibrium
• which method of making ethanol is better?

  Fermentation:

  -> raw materials are renewable - better for environment, crude oil not renewable

  -> lower temp. & atmospheric pressure - less energy used - cheaper

  However:

  -> slow for mass production

  -> impure ethanol produced - energy required for fractional distillation, other reaction produces pure
• How can you make an accurate concentration?

  Use a volumetric flask which is calibrated o a specific volume
• How do you make a solution?

  solute dissolved in distilled water, made up to graduation mark, stoppered and shaken.
• Concentration calculation:


  concentration = mass of solute / volume of solution
• In the normal concentration calculation, what is concentration, mass & volume measured in?

  concentration = (g dm^-3)

  mass = (g)

  volume = (dm^3)
• concentration in moles calculation:

  concentration = no. of moles of solute / volume of solution
• In the moles concentration calculation, what is concentration & volume measured in?

  concentration = (mol dm^-3)

  volume = (dm^3)
• The two concentrations are linked by:

  concentration (mol dm^-3) = concentration (g dm^-3) / Mr of solute
• Convert cm3 to dm3

  divide by 1000
• convert dm3 to cm3

  x 1000
• What are acid-alkali titrations used for?


  to find the 𝗲𝘅𝗮𝗰𝘁 ��𝗼𝗹𝘂𝗺𝗲 of an 𝗮𝗰𝗶𝗱 that 𝗻𝗲𝘂𝘁𝗿𝗮𝗹𝗶𝘀𝗲𝘀 a 𝘀𝗽𝗲𝗰𝗶𝗳𝗶𝗰 𝘃𝗼𝗹𝘂𝗺𝗲 of an 𝗮𝗹𝗸𝗮𝗹𝗶 (𝘷𝘪𝘤𝘦 𝘷𝘦𝘳𝘴𝘢)
• What are the steps for titration calculations?

  -> 𝗦𝗧𝗘𝗣 𝟭: calculate 𝗻𝘂𝗺𝗯𝗲𝗿 𝗼𝗳 𝗺𝗼𝗹𝗲𝘀 of solution that you know the volume of & concentration

  -> 𝗦𝗧𝗘𝗣 𝟮: use 𝗯𝗮𝗹𝗮𝗻𝗰𝗲𝗱 𝗲𝗾𝘂𝗮𝘁𝗶𝗼𝗻 (ratio) to work out 𝗻𝘂𝗺𝗯𝗲𝗿 𝗼𝗳 𝗺𝗼𝗹𝗲𝘀 of solution you don't know volume of

  -> 𝗦𝗧𝗘𝗣 𝟯 : calculate 𝗰𝗼𝗻𝗰𝗲𝗻𝘁𝗿𝗮𝘁𝗶𝗼𝗻 of unknown solution
• what is the colour change for methyl orange?

  yellow-peachy/orange

  
• What are concordant results?

  results within 0.2 cm³ of each other
• the volume taken up by a gas sample depends on...

  temperature, pressure and number of gas particles, NOT the Mr
• What is Avogadro's Law?

  equal volumes of gases contain equal numbers of molecules if the temperature and pressure are the same
• what is the molar gas volume at rtp?

  24 dm^3
• how do you find the amount of gas (mol)?

  volume of gas/molar volume(24 dm^3 rtp)
• plants absorb____________ through their _______. This decreases the _________ of these in the soil

  mineral ions, roots, concentration
• what would happen to plants with no mineral ions?

  may not grow properly, suffer from deficiency diseases
• Fertilisers________ mineral ions


  replace
• three most important mineral nutrients for plants

  nitrogen, phosphorus, potassium
• why must N, P, K be provided as soluble compounds?

  Because root hair cells only absorb mineral ions that are dissolved in water
• name 2 nitrogenous fertilisers

  ammonium nitrate, ammonium sulphate
• give the word equation for making nitric acid from ammonia

  ammonia + oxygen -> nitric acid + water
• give the word equation for making ammonium sulphate

  ammonia + sulfuric acid -> ammonium sulphate
• for lab preparation, the reactants are bought from...

  chemical manufactures