C3- Chemical Economics Flashcards
What does rate of reaction measure?
How much product is formed in a fixed period of time
Why do reactions usually slow down at the end?
As the reactants are used up
What are the common units for measuring rates of reactions?
- g/s grams per second (faster reactions) and g/min grams per minute (slower reactions) when measuring mass of product formed
- cm3/s centimetre cubed per second (faster reactions) and cm3min centimetre cubed per minute (slower reactions) when measuring volume of gas produced
How can you calculate rate of reaction from a graph?
Using the gradient of a graph
- choose a part of the graph where there is a straight line
- measure the value of y and x
- divide y by x
What is the equation for calculating the gradient?
Gradient = y/x
What is the limiting reactant?
The reactant not in excess that gets used up by the end of the reaction
What is the connection between the amount of product formed in a reaction and the amount of limiting reactant used?
They are directly proportional
What takes place when particles collide?
Chemical reactions
What does the rate of reaction depend on?
Number of collisions between the reacting particles: higher the numebr of collisions, faster the rate of reaction
How does increasing concentration affect rate of reaction?
- concentration increases
- particles become more crowded
- increases number of collisions between reacting particles
How does increasing temperature affect rate of reaction?
- temperature increases
- particles gain kinetic energy
- move quicker
- collisions between reacting particles are more successful
- rate of reaction increases
How does increasing pressure affect rate of reaction?
Particles are closer together, so increases rate of reaction
What is collision frequency?
Number of successful collisions between reacting particles each second
For successful collisions to occur, what must the particles have?
Enough energy
What can cause explosions?
Combustible powders
How combustible powders cause explosions?
- some powders react with oxygen to make large volumes of carbon dioxide and water vapour
- owners of a factory using combustible powders (flour, custard powder or sulfur) must be careful. Ensure powders can’t reach open atmosphere and chances of sparks is very small
What can increase surface area?
Breaking the substance into smaller pieces
Which would have a larger surface area: powdered reactant or blocked reactant?
Powdered reactant
How would surface area affect rate of reaction?
Small surface area:
- most particles in the solid block cannot react as collisions can only occur at the surface
Large surface area:
- more surfaces on these particles are exposed, so more collisions are possible, increasing rate of reaction
How does a catalyst affect the rate of reaction?
Speeds up the rate of reaction and is unchanged at the end
How do you decide which catalyst to use for a reaction?
Each catalyst is specific for a particular reaction
How do you work out the relative formula mass of an element?
Using the periodic table, add the atomic masses (Ar) to calculate the relative formula mass (Mr)
What is the relative atomic mass of Ca(NO3)2?
Ca=40 N=14 O=16
14 + (16 x 3)= 62
62 x 2 = 124
124 + 40 = 164
What is conservation of mass?
Total mass of reactants = total mass of products
Why is mass conserved?
Atoms cannot be created or destroyed, only rearranged into different compounds
How do you calculate percentage yield?
Why do industrial processes need a high percentage yield?
- reduce amount of reactants wasted, which is wasteful and costly
- reduce costs by ensuring that enough reactants are used, as too little reduces amount of product
How do you calculate atom economy?
Why do industrial processes need a high atom economy?
- reduce production of unwanted products tha will need to be disposed of (which often adds to overall costs)
- make the process more sustainable by making better use of reactants, so conserving raw materials and avoiding the need to get rid of wasted products
What is an endothermic process?
Bond breaking
What is an exoothermic process?
Bond making
How can you tell which reaction is endothermic and which is exothermic?
- energy is needed to break reactants into separate atoms
- atoms join to form new bonds, releasing energy
If more energy is released than needed, the reaction is exothermic
If more energy is needed than released, the reaction is endothermic
How can you calculate energy transferred by a fuel?
What can you do to find out the energy released by 1g of solid fuel?
- measure out the mass of 1g of fuel
- pour 100g water into a copper calorimeter (1 cm3 of water = 1g)
- heat the water with burning fuel
- measure the temperature rise
- repeat with different fuels for fair testing
- ensure reliability by repeating results
How can you measure energy per gram of fuel?
Energy per gram =
energy released (J) / mass of fuel burnt (g)
What is continuous process?
- makes large amounts of product 24 hours a day, seven days a week
- takes place in a large chemical plant with good transport links; plants are highly automated so have minimal labour costs, making product cheaper
- takes less energy to maintain - as long as the process can be kept running- than to stop and start the process
What is made using continuous processing?
Ammonia and sulfuric acid
What is batch process?
- makes a fixed amount
- allows batches to be made and stored until needed
- allows quantities to be made that can be sold within a given time as many drugs have a ‘sell by’ date
- easy to make a new batch when needed
- easy to change production to a different product
What is made using batch processing?
Medicines and drugs
What are the disadvantages with continuous processing?
- process is ineficient if not in constant use
- high initial building and set-up cost for these chemical plants
What are the disadvantages with batch processing?
- each batch has to be supervised so it is labour intensive and very costly
- time is needed for cleaning if product line is changed
- it is inefficient as production is not in use all the time
What are the developmental costs of drug making?
- it can take about 10 years to develop and test a new drug and each country has strict safety laws that pharmaceutical companies must follow
- many compounds need to be made before one may be used to develop
- raw materials are often rare and costly
- raw materials are found in plants, and are difficult to extract
How can you extract a chemical from a plant?
- crushing to disrup and break cell walls
- boiling in a suitable solvent to dissolve compounds
- chromatography to separate and identigy individual compounds
- isolating, purifying and testing potentially useful compounds
What does chromatography test?
Purity of a compound by comparing the speed of movement against a known pure sample
Why is it difficult and costly to get a licence for a new drug?
- thousands of compounds often need to be tested to find effective ones
- likely compounds need to be tested on living tissue to endure safety
- long term trials on humans are needed to identigy possible side effects
- many similar compounds need to be developed to try to reduce side effects
- recommended doses need to be shown to be effective
- the research needs to be independently verified
- patents expire before costs are recouped and others can make a version
What do diamond, graphite and fullerenes have in common?
They are all allotropes of carbon
What are allotropes?
Different structures of the same element
What are fullerenes?
Carbon structures that form spheres or tubes and can be used:
- to carry and deliver drug molecules around the body
- to trap dangerous substances in the body and remove them
What is a buckminsterfullerene?
Contains 60 carbon atoms in a sphere. Its formula is C60. Each sphere is so small it is measured in nanometres (10-9 metres long)
What are diamonds and graphite?
Giant covalent structures of carbon atoms
What are the carbon atoms bonds in diamond?
They make very strong covalent bonds in different directions
What are the carbon atom bonds in graphite?
Carbon atoms bond to make layers
What are the properties of diamond?
- hardest natural substance
- very high melting point and boiling point
What is diamond used for?
- cutting tools
- jewellery (facests reflect light)
What are the properties of graphite?
- very high melting point and boiling point
- layers can slide over each other
What is graphite used for?
- pencils
- high temperature lubricant
What does giant covalent bonding involve?
Electron sharing
How does diamond share electrons?
Every carbon atom in diamond is covalently bonded to four others in a three-dimensional tetrahedral lattice with all the outer shell electrons being shared
How does diamond’s structure give it specific properties?
- strong covalent bonds in all directions make diamond hard. Large amounts of energy are required to break the bonds, giving a high melting point of 3350°C
- an absence of free electrons, meaning diamond does not conduct electricity
How does graphite share electrons?
Every carbon atom in graphite is covalently bonded to three others in flat hexagonal layers. This formation leaves an unshared outer shell electron. This delocalised electron is free to move long the layer. The separate layers are only weakly attracted to each other
How does graphite’s structure give is specific properties?
- strong covalent bonds give graphite a melting point similar to diamond
- delocalised electrons make it a good electrical conductor
- when force is applied, the weak forces between layers slide over each other; this slippery nature makes it an ideal high-temperature lubricant
What do giant covalent bonding form compounds with?
Millions of very strong fixed bonds
What are the properties of giant covalent structures?
- high melting point
- if bonds are formed in different directions, substance is hard
- if bonds form in layers, it will be easy to cut in slices
- if there are not free electrons, substance will not conduct electricity
What are nanotubes?
Carbon atoms formed in a very tiny tube
How can nanotubes be used in catalyst systems?
Atoms of the catalyst can be attached to the large surface areas on the nanotubes
