C3.2 Flashcards
What is predicted yield?
How much product should be made
What is the actual yield?
The amount really produced from a product
Percentage yield = ?
actual yield
———————- X 100
predicted yield
How can the actual yield be calculated?
Relative formula mass
Why is the actual yield produced less than the predicted?
Due to losses in the practical methods
Why do industrial processes have to have a high percentage yield?
- To reduce the amount of reactants wasted, which is costly
2. Reduce their cost by ensuring enough reactants are used
Atom economy = ?
mass of atoms in desired product
————————————————- X 100
mass of all products
Why does the industry want a high atom economy?
- To reduce the production of unwanted products that will need to be disposed of (adds to the cost)
- To make the process more sustainable by making better use of the reactants
What is an endothermic process?
Bond breaking
What is an exothermic process?
Bond making
How do you decide whether a chemical reaction is exothermic or endothermic?
The amount of energy made and produced need to be compared
How can bond energy changes be represented?
Diagrams
What are the steps to find out if a reaction is exothermic or endothermic?
- Energy is needed to break reactants into separate atoms
- Atoms join to form new bonds releasing energy
|f more energy is released than needed, the reaction is exothermic
If more energy is needed than released, the reaction is endothermic
Energy transferred = ?
mass x specific heat capacity x temperature change
Energy per gram = ?
mass of fuel burnt
Give examples of chemicals made using continuous processes? (needed in large quantities)
Ammonia and sulfuric acid
What are the properties of continuous processing?
- Makes large amount of product 24 hours a day, 7 days a week
- Takes place in large chemical plants with good transport links. Plants are highly automated = minimal labour cost = product cheaper
- Takes less energy to maintain
How are chemicals that are needed in small quantities such as medicines made?
Batch processes
What are the properties of batch processing?
- 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
- Makes it easy to buy a new batch
- Makes it easy to change production to a different product
What is the advantage of continuous processing?
Cost per tonne is very small
What are the disadvantages of continuous processing?
- The process is inefficient if not in constant use
2. There is a very high initial building and set-up cost for these chemical plabts
What is the advantage of batch processing?
Flexibility
What are the disadvantages of batch processing?
- Each batch has to be supervised so its labour intensive and costly
- Time is need for cleaning if the product line is changed
- It is inefficient as the production is not in use all the time
Why are medicines so expensive?
- It takes about 10 years to develop a drug and there’s strict pharmaceutical laws that each country follows
- Many compound need to be made before one may be useful to develop
- Raw materials are often rare and costly
- Many raw materials are found in plants and are difficult to extract
How do you extract a chemical from a plant ?
- Crushing to disrupt and break cell walls
- Boiling in a suitable solvent to dissolve the compounds
- Chromatography to separate and identify individual compounds
- Isolating, purifying and testing potentially useful compounds
What do pure compounds have?
Definite melting and boiling points
What is chromatography?
A thin layer that is used to test the 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 needs need to be tested on living tissue to ensure safety
- Long-term trials on humans are used to identify possible side effects
- Many similar compounds need to be developed to try to reduce side effects
5, Recommended does need to be shown effective
- The research needs to be independently verified
- Patents expire before costs are recouped and others can make a version
What are allotropes?
Different structures of the same element
Give examples of allotropes
Diamonds., graphite and fullerene
What are fullerenes?
Carbon structures that form spheres or tubes
What is fullerene used for?
- To carry and deliver drug molecules around the body
2. To trap dangerous substances in the body and remove them
Why is diamond useful?
It is the hardest natural substance known and has a very high melting and boiling point
Why is graphite useful?
It has a high melting and boiling point, but the layers can slide over each other. It is used in pencils and a high temperature lubricant
What do graphite and diamond have in common?
They both have giant covalent structures of carbon atoms
What does giant covalent bonding involve?
Electron sharing
What is the structure of diamond?
- Strong covalent bonds in all directions making it hard
2. An absence of free electrons which means diamonds don’t conduct electricity
What is the structure of graphite?
- Strong covalent bonds give graphite a melting point similar to diamond
- The delocalised electrons make it a good electrical conductor
- When force is applied, the weak forces between the layers slide over eachother; this slippery nature makes it an ideal high-temperature lubricant
What advantages/disadvantages do elements with giant covalent bonding have?
- High melting point
- No free electrons = does not conduct electricity
- Bonds are formed in different directions = substance is hard
- Bonds form in layers = easy to cut in slices
What can nanotubes be used for?
catalyst systems
