C3 - Chemical economics

Rate of reaction = how much product is formed in a fixed period of time

• calculated by finding the gradient = y / x

Limiting reactants:

• = the reactant not in excess that gets used up by the end of the reaction
• amount of product formed is directly proportional to the amount of limiting reactant used
• if number of reacting particles of one reactant is limited, the number of collisions by particles of that reactant is also limited

Rate of reaction depends on:

• collision frequency - the number of successful collisions between reacting particles each second
• higher number of collisions = faster reaction

Rate of reaction is increased by:

• higher concentration - as concentration increases the particles become more crowded which increases the number of collisions between reacting particles
• higher temperature - as the temperature increases, the particles have more kinetic energy and move around more quickly so collisions between particles are more successful and collide more frequently
• higher pressure - increasing the pressure forces particles closer together which increases the rate of reaction as there are more frequent collisions

Increasing surface area of a reactant also increases rate of reaction:

• Small surface area: (reactant in solid block form)
  • the reactant collides with the other reactant on the surface only which results in a slower rate of reaction
• Larger surface area: (reactant in powdered form)
  • more surface area exposed to reactant so more collisions are possible with more of the reactant increasing the rate of reaction
• powders spread throughout a reaction mixture which increases the collsion frequency

Catalysts:

• speeds up the rate of reaction but remains unchanged at the end of the reaction
• small quanitites of catalyst is needed to catalyse a large mass of reactants

Relative atomic mass = largest number shown on periodic table

Relative formula mass = total of relative atomic masses of a compound

Conservation of mass:

• total mass of reactants = the total mass of products

Percentage yield = 

Percentage yield should be as high as possible so that they:

• reduce amount of reactants wasted which is costly
• reduce costs by ensuring enough reactants are used as too little reduces amount of product

Atom economy = 

Industry wants as high an atom economy as possible to:

• reduce production of unwanted products that need to be disposed of which adds to overall costs
• make process more sustainable by making better use of reactants

Making and breaking bonds:

• bond breaking  = endothermic
• bond making = exothermic
  • stage 1: energy is needed to break reactants into seperate atoms
  • stage 2: atoms join to form new bonds
  • if more energy is released than needed, the reaction is exothermic
  • if more energy is needed than released, the reaction is endothermic

Energy released by fuels:

• mass x specific heat capacity x temperature change

Energy released by 1g of solid fuel:

• measure out 1g of fuel
• pour 100g of water into copper calorimeter
• heat water with burning fuel
• measure temperature rise
• repeat with different fuels to ensure fair testing
• repeat results for reliability

Energy in a gram of fuel:

• energy released (in J) / mass of fuel burnt (in g)

Continuous processing: makes large amount product 24/7 in highly automated chemical plants

• advantages:
  • minimal labour costs = cheaper prodcut
  • less energy to maintain
• disadvantages:
  • process is inefficient if nto in constant use
  • hgih initial building and set up cost

Batch processing: fixed amount of product made

• advantages:
  • batches made and stored until needed
  • easy to make new batch and change production to different product if needed
• disadvantages:
  • each batch is supervised so its labourintensive and costly
  • inefficient as production line is not in use all the time

Why medicines are expensive:

• takes years to develop and test new drugs
• many compounds needed to be made before one is useful to develop
• raw materials are rare and costly
• many raw materials are found in plants and difficult to extract and this involves:
  • crushing to break cell walls
  • boiling in solvent to dissolve compounds
  • chromotography to seperate and identify individual compounds
  • isolating, purifying and testing potentially useful compounds
• pure compounds have definite melting and boiling points

Licenses for new drugs are difficult and costly to get because:

• thousands of compounds need to be tested to find effective ones
• long term trials on humans are needed to identify possible side effects
• research needs to be independently verified

Allotropes of carbon:

• Diamonds: used in jewelry and cutting tools
  • three dimensional tetrahedral lattice, strong covalent bonds in all direction making it hard
  • large amounts of energy required to break bonds giving it a high melting and boiling point
  • an absence of free electrons, meaning it doesn't conduct electricity
• Graphite: high temperature lubricant
  • flat hexagonal layers slide over each other because seperate layers are weakly attracted
  • high melting and boiling point because of strong covalent bonds
  • delocalised electrons make it good electrical conductor
• Buckministerfullerene: used to carry and deliver drug molecules around body ad trap dangerous substances in the body and remove them
  • 60 carbon atoms in a sphere - C60, measured in nanometres

Nanotubes used in catalyst systems - atoms of catalyst attached to large surface areas on nanotubed