C7- Further Chemistry Flashcards
What are fine chemicals?
Chemicals produced on a smaller scale.
For example, drugs, food additives and fragrances.
Researching chemical products?
To make a new production process run efficiently a new catalyst might have to be found:
- Testing potential catalysts using a process of trail and error.
- Making computer models of the reactions to try to work out which substance might work as a catalyst.
- Designing or refining the manufacture of the catalyst to make sure that the new product can be mass produced safely, efficiently and cost effectively.
- Investigating the risks to the environment of using the new catalyst and trying to minimise them.
- Monitoring the quality of the product to make sure that it is not affected by the catalyst.
Regulations the government set to protect the environment?
- Using chemicals- Government regulations restrict how much a substance can be used and require signs to be displayed to warn the public.
- Storage- Many dangerous chemicals have to be stored in locked storerooms. Poisonous chemicals must be stored in either sealed containers or well ventilated store cupboards.
- Transport- Transporting vehicles must display hazard symbols and indentification numbers to help the emergency services deal safely with any accidents.
Stages of the production of chemicals?
- Preparation of feedstock- Raw materials are the naturally occurring substance which are needed. Feedstock are the actual reactants needed for the process. The raw materials have to be purified or changed in some way to make the feedstock.
- Synthesis- The feedstock (reactants) are covered into products. The conditions have to be controlled to make sure the reactions happens at a sensible rate.
- Separation of products- The by products and left over reactants are separated out so they can be dealt with differently.
- Purity of product- After the separation, it is not completely pure. The purity of the product is monitored to make sure it’s between certain levels. However if it’s only slightly impure then they don’t purify it as it wastes money.
- Handling the waste- Some by products are sold or used in other reactions. If the reaction is exothermic there is waste heat.
Heat exchanges can use excess heat to produce steam or hot water for other reactions. This saves money and energy.
Waste products are carefully disposed so they don’t harm people or the environment. There are legal retirements about this.
What are “by products”?
Chemical reactions usually produce the substance you want and other chemicals known as by products.
They can be useful or a waste.
8 questions about sustainability?
• Will raw materials run out?
If the feedstock is renewable you can use it as much as you like. If it’s non renewable it will run out. This is a problem for future generations.
• How good is the atom economy?
The atom economy of a reaction tells you how much of the mass of the reactants ends up as useful products. If you make waste it will have to go somewhere. Reactions with low atom economy use up resources quickly.
• What happens to the waste products?
Waste products can be expensive to remove and dispose of. They will take up space and cause pollution. So we have to use waste products instead.
• What are the energy costs?
If a reaction needs a lot of energy it will be expensive. Providing energy involves burning fossil fuels. If a process gives out energy- you could use the energy for something else- saving money and environment.
• Will it damage the environment?
If the reaction produces harmful chemicals it’s bad for the environment. However, where the raw materials come from need to be considered and if the products or reactants need transporting.
• Health and safety risks?
There are laws that companies must follow to make sure the workers and the public are not put in harm. Companies must test their products to make sure their safe.
• Benefits or risks to society?
A factory creates jobs for local community and brings money to the area. However, it can be hazardous.
• Is it profitable?
If the costs of a process are higher than the income from it then it won’t be profitable.
Breaking bonds?
- During a chemical reaction old bonds are broken and new bonds are formed.
- Energy must be supplied to break existing bonds- so bond breaking is an endothermic process.
- Energy is released when new bonds are formed so bond formation is an exothermic process.
- In exothermic reactions the energy released by forming bonds is greater than the energy used to break them.
- In endothermic reactions the energy used to break bonds is greater than the energy released by forming them.
Bond energy calculations?
(Look in CGP book)
Activation energy?
- The activation energy is the minimum amount of energy needed for bonds to break and a reaction to start.
- If the energy input is less than the activation energy there won’t be enough energy to start the reaction- so nothing happens.
Catalyst activation energy?
- A catalyst is a substance which changes the speed of a reaction without being used up in the reaction.
- Catalyst lower the activation energy needed for reactions to happen by providing alternative routes.
- The effect of a catalyst is shown by the lower curve on the diagram.
- The overall energy change for the reaction remains the same.
Reversible reaction?
A reversible reaction is one where the products of the reaction can themselves react to produce the original reactants.
Dynamic equilibrium?
- If a reversible reaction takes place in a closed system then a state of equilibrium will always be reached.
- Equilibrium means the relative (%) quantities of reactants and products will reach a certain balance and stay there.
- A dynamic equilibrium- means that the reactions are still taking place in both directions but the overall effect is nil because the forward and reverse reactions cancel each other out.
- The reactions are taking place at exactly the same rate in both directions.
What’s a closed system?
Means that none of the reactants or products can escape.
The haber process?
- The feedstocks for the Haber process are nitrogen & hydrogen.
- The nitrogen is obtained from the air which is 78% nitrogen.
- The hydrogen comes from the cracking of chemicals in natural gas using steam.
- The reaction is reversible so not all the nitrogen and hydrogen will convert to ammonia.
- The gases don’t stay in the reaction vessel long enough for the reaction to reach equilibrium.
- The nitrogen and hydrogen which don’t react are recycled an passed through again so none is wasted.
- Recycling nitrogen and hydrogen means more ammonia will be produced using the same amount of reactant
- The yield of ammonia will increase.
Industrial conditions?
Pressure: 200 atmospheres
Temperature: 450 degrees
Catalyst: iron
( the iron catalyst is used to make the rate of reaction faster)
How ammonia is produced?
- Higher pressures favour the forward reaction.
- The pressure is set high as possible to give the best % yield without making the plant too expensive to build.
- Hence the 200 atmospheres operating pressure.
- The forward reaction is exothermic which means that increasing the temperature will move the equilibrium the wrong way- away from ammonia and towards nitrogen & hydrogen.
- The yield of ammonia would be greater at lower temperatures.
- However, lower temperatures mean a slower rate of reaction. They increase the temperature to get a faster rate of reaction.
- The 450 degrees is a compromise between maximum yield and speed of reaction.
- The unused hydrogen and nitrogen are recycled so nothing is wasted.
Nitrogen fixation?
- Is the process of turning nitrogen from the air into useful nitrogen compounds like ammonia.
- The Haber process is a non biological way of fixing nitrogen.
- Most of the ammonia produced by the Haber process is used to make fertilisers.
- Fertilisers are important in world food production a hey increase crop yield and feed more people.
- Of there is a large amount of fertilisers it can pollute water supplies & cause eutrophication.
- Eutrophication happens when fertilisers leach into rivers and lakes- stimulating rapid algal growth.
- The algae blocks out light to other plants which then die.
- Microorganisms then feed on the dead plants - using up all the oxygen that aquatic animals need to survive.
- Eventually, all of the plant and animal life in the water dies.
- Ammonia is important in industry where it is used to manufacture plastics, explosives and pharmaceuticals.
Efficiency of nitrogen fixation improved by catalyst?
- In the Haber process very high temperatures and pressures have to be used to turn nitrogen and hydrogen to ammonia.
- Using an iron catalyst makes the rate of reaction faster- so ammonia is produced faster.
- Without the catalyst the temperature would have to be raised even further to get a quick reaction and that would reduce the % yield even further.
- Living organisms like nitrogen fixing bacteria can fix nitrogen at room temperature and pressure. They do this using enzymes.
- Chemists would like to be able to make catalyst which mimic the enzymes. So the processes like Haber process can be don’t at room temperature and pressure.
- Its expensive and time consuming to work at high temperatures and pressures.
- This would mean that processes involving nitrogen fixing would become cheaper and more efficient.
Nitrogen fixation sustainability questions?
• Will the raw materials run out?
Hydrogen comes from fossil fuels. They’re non renewable and will run out. Nitrogen comes from air so it’s unlikely it will run out.
• How good is the atom economy?
All the hydrogen and nitrogen makes ammonia so the atom economy is good.
• What do I do with the waste products?
There are no waste products as the chemicals are all recycled.
• What are the energy costs?
Lots of energy is needed to keep the reaction at 450 degrees and 200 atm.
• Will it damage the environment?
Fertilisers made from NH3 can cause eutrophication and water pollution.
• What are the health and safety risks?
Working at high temperatures and pressures can be dangerous.
• Are there any benefits of risks to society?
Making ammonia will help world food production.
• Is it profitable?
Yes, making ammonia is a big business!
Alkanes?
- Alkanes are made up of chains of carbon atoms surrounded by hydrogen atoms.
- Alkanes contain single covalent bonds between carbon atoms. They are saturated compounds.
- The alkane family contains molecules that look similar but have different length chains of carbon atoms.
- All Alkanes have the formula in the picture above. (Look in CGP book)
Methane?
(Look in CGP book for formula)
Ethane?
(Look in CGP book)
Propane?
(Look in CGP book)
Butane?
(Look in CGP book)
What do alkanes produce when burnt?
Alkane+oxygen —> CO2+ water.
Alkanes burn to produce carbon dioxide and water- if there is enough oxygen around.
Do Alkanes react with other chemicals?
- Alkanes are unreactive towards most chemicals.
- They don’t react with aqueous reagents (substances dissolved in water)
- Alkanes don’t react because the C-C bonds and C-H bonds in them are difficult to break.
Alcohols and formula??
- The general formula for an alcohol is in the above pic.
- Methane- CH3OH
- Ethanol- C2H5OH
- The “-OH” is called the functional group.
- All alcohols have similar properties because they all have the -OH functional group.
Similarities and differences between Alkanes and alcohols?
- Ethanol is soluble in water. Alkanes are insoluble in water.
- Ethanol and water are both good solvents- lots of things dissolve in them.
- The boiling point of ethanol is 78 degrees Celsius.
- The boiling point of water is 100 degrees Celsius.
- The boiling point of Alkanes is -103 degrees Celsius.
- Ethanol is a liquid at room temperature. It evaporates easily and gives off fumes.
- Methane and ethane are volatile but gases at room temperature.
- Water is liquid at room temperature but not volatile.
Alcohols are solvents?
- Alcohols like methanol and ethanol can dissolve lots of compounds that water can’t.
- This makes methanol and ethanol useful solvents in industry.
- Methanol is used in the industry as a starting point for manufacturing other organic chemicals.
- Ethanol is used in perfumes and aftershave lotions as it can mix with both the oils and the water.
- “Methylated spirit” is ethanol with chemicals added to it. It’s used to clean paint brushes and as a fuel.
- Alcohols burn in air to produce carbon dioxide and water because they contain hydrocarbon chains.
- Pure ethanol is clean burning so it is sometimes mixed with petrol and used as fuel for cars to conserve crude oil.
