C7 Flashcards
The government puts strict controls on everything to do with chemical processes to protect what?
To protect workers, the general public and the environment.
Bulk chemicals are?
Chemicals that are produced on a large scale.
Give three regulations that the government controls of chemical processes.
1) Using chemicals- they restrict how much can be used and require signs to warn public.
2) Storage- poisonous chemicals must be stored in either sealed containers or well- ventilated store cupboards.
3) Transport- lorries transporting chemicals must display hazard symbols and identification numbers.
Give the five different stages involved in producing chemicals.
1) Preparation of feedstock
2) Synthesis
3) Separation of products.
4) Monitoring the purity if product
5) Handling of by-products and wastes.
First step of chemical synthesis: why are raw materials converted into feedstocks?
Raw materials are naturally occurring substances which are needed.
Feedstocks are the actual reactants needed for the process.
The raw materials are purified or changed some way to make feedstocks.
The second stage of producing chemicals: synthesis.
Feedstocks are turned into products. The conditions are carefully controlled to make sure the reaction happens and at a good rate.
Step 3 of producing chemicals: the products are separated
Once the chemical reaction is done, you will get the substance you want and other chemicals you don’t want and leftover reactants.
Everything has to be separated out so it can be dealt with in different ways.
4th step in producing chemicals: purity of product monitored
Different industries need different levels of purity depending on what the product will be used for.
If a slightly impure product will do the job it is meant for, there’s no point wasting money on purification.
5th step of producing chemicals: by products are dealt with
By-products are used in another reaction or sold.
Waste heat can be used for other reactions to save energy and money.
Waste products are carefully disposed of and regulated by the government so they do not harm people or environment.
A + B ——-> AB =
= exothermic
AB ———> A + B =
= Endothermic
What type of reaction is one when the energy released by forming bonds is greater than the energy needed to break them?
Exothermic
What type of reaction is one that when the energy used to break bonds is greater than the energy than the energy released by forming them?
Endothermic
Activation energy=
= the minimum amount of energy needed for bonds to break and a reaction to start.
What happens if the energy input is less than the activation energy?
Nothing will happen.
How do catalysts lower the activation energy?
Catalyst lower the activation energy needed for reactions to happen by providing alternative routes.
What’s a catalyst?
A substance which changes the speed of the reaction, with ought being used up itself.
What is reversible reaction?
One where the products of the reaction can themselves react to produce the original reactants.
A + B —–> C + D
<——
What happens when an equilibrium is obtained?
The relative (%) quantities of reactants and products will reach a certain balance and stay there.
What is a dynamic equilibrium?
The reaction is taking place in both directions, but the overall effect is nil because the forward and reverse reactions cancel each other out.
N2 + 3H2 —–>
2NH3
What are the industrial conditions for the Haber process?
Pressure:200 atmospheres
Temperature: 450 degrees
Catalyst: Iron
Where his nitrogen and hydrogen found for the Haber process
Nitrogen is easily found as it takes up 78% of the atmosphere.
Hydrogen comes from the cracking of chemicals in natural gas using steam.
Describe why the industrial conditions for the Haber process are set how they are.
Pressure: higher pressures favour the forward reaction, so the pressure is set as high as possible to give best % yield without making the plant to expensive to build.
Temperature: Higher temperatures favour the endothermic reaction, so lower temperatures work better. However, low temperatures will give a slow rate of reaction so they increase the temperature anyway.
Iron: Is a catalyst, helps speed up reaction.
What is nitrogen fixation?
Is the process of turning N2 from the air into useful nitrogen compounds like ammonia.
Why do chemists want to be able to mimic enzymes such as nitrogen- fixing bacteria?
So that processes like the Haber process can be carried out at room temperature.
Is nitrogen fixation a sustainable process?
1) will the raw materials run out?
2) how good is the atom economy?
3) what do I do with my waste products?
4) what are the energy costs?
5) will it damage the environment?
6) what are the earth and safety risks?
7) are there any benefits and risks to society?
8) Is it profitable?
1) hydrogen comes from fossil fuels which are non- renewable
Nitrogen comes form the air and will most likely not run out.
2) there is no waste in the reaction, so the atom economy is good.
3) there are no waste products because they are recycled.
4) lots of energy us needed to keep the reaction at high temperatures and pressures.
5) fertilisers made from nitrogen and hydrogen cause eutrophication.
6) working at high temps and atmospheres can be dangerous
7) making ammonia helps food production
8) yes, ammonia making is a big business.
What are alkanes made of?and are they saturated or unsaturated?
Alkanes are made up of chains of carbon atoms surrounded by hydrogen atoms.
The only contain single covalent bonds between carbon atoms so they are saturated.
What is the formula for all alkanes?
Cn + H2n + 2
Give the molecular formula for methane,ethane,propane and butane.
Methane: CH4
Ethane: C2H6
Propane: C3H8
Butane: C4H10
Alkanes burn to produce what?
To produce carbon dioxide and water
Alkane+ oxygen–> carbon dioxide+ water
What do alkanes not react with?and why?
They do not react with aqueous reagents( substances dissolved in water).
Alkanes don’t react because the C-C bonds and C-H bonds are difficult to break.
What is the general formula for an alcohol?
CnH2n+1OH
Name the two first alcohols and their chemical formula.
Methanol - CH3OH
Ethanol - C2H5OH
Compare alcohols with alkanes and water in terms of their physical properties.
1) Ethanol is soluble in water. Alkanes are insoluble
2) Ethanol and water are both good solvents.
3) boiling point of ethanol is 78 C . Boiling pint of water is 100 C
4) Ethanol is a liquid at room temperature, it’s also volatile. Methane and ethane are also volatile, but are gases at room temperature.
Name several uses for alcohols and why are they so useful?
They can dissolve a lot of compounds that water can’t like hydrocarbons and oils.
Used to make perfumes, methylated spirit, paint cleaner, fuel for cars.
What is fermentation?
Fermentation uses yeast to convert sugars into ethanol. Carbon dioxide is also produced.
Yeast
Sugar————> ethanol carbon dioxide
Describe the zymase contained in yeast cells.
Yeast cells contain zymase, an enzyme that acts as a catalyst in fermentation.
Fermentation works best at 39 degrees because zymase works best at this temperature.
If it gets to hot the zymase becomes denatured.
Zymase works best at an PH of 4.
Why is it important to prevent oxygen getting into the fermentation process?
Because oxygen converts the ethanol to ethanoic acid, which lowers the PH and can stop the enzyme working.
When the concentration reaches about 10 to 20%, the fermentation reaction stops, because the yeast gets killed by the ethanol.
Explain how ethanol solution can be concentrated by distillation.
1) the ethanol solution is put in a flask below a fractioning column.
2) the solution is heated so the ethanol boils.The ethanol vapour travels up the column, cooling down as it goes.
3) the temperature is such that anything with a higher boiling point than ethanol( like water) cools to a liquid and flows back to the solution at the bottom.
4) this means that only pure ethanol vapour reaches the top of the column.
5) the ethanol flows through a condenser- where it is cooled to a liquid which is then collected.
Explain how ethanol can be made from biomass.
Waste biomass is the parts of plants that are normally throw away.
Waste biomass cannot be fermented in the normal way because it contains a lot of cellulose( yeast can only convert sugars).
E.coli bacteria can be genetically modified so they can convert cellulose in to waste biomass into ethanol.
The optimum conditions for this process are a temperature of 35 C and pH 6.
How similar is the sustainability of the biomass method to the standard fermentation method?
Very similar because they both use similar processes.
The advantage of using biomass is that you don’t have to grow crops specially for producing ethanol- you can use the waste from other crops.
Explain how ethane can be reacted to make Ethanol.
Fermentation is to slow for making ethanol on a large scale.
Ethane is one of the hydrocarbons found in crude oil and natural gas.
It is ‘cracked’ to form ethane and hydrogen gas.
Ethene will react with steam (H2O) to make ethanol.
The temperature needed for the reaction is 300Celsius and a pressure of 70 atmospheres.
Phosphoric acid is used as a catalyst.
What is carboxylic acids function group?
‘COOH’
Carboxylic acids react with metals to give what?
To give a salt and hydrogen.
Carboxylic acids react with carbonates to give what?
A salt, water and carbon dioxide.
Carboxylic acids react with alkalis to form what?
A salt and water.
Why does wine and beer taste rancid when left in the air?
The ethanol reacts with the oxygen to produce ethanoic acid which gives the strong smell and taste.
What is the functional group of Esters?
-COO-
Give all the uses for Esters.
Many esters have pleasant smells- often sweet and fruity.
They are also quite volatile , makes the ideal for perfumes.
Some esters are used as solvents for paint, in, and glue.
Esters are also used as plasticisers- they are added to plastics to make them more flexible.
