C7 - Further Chemistry Flashcards
Fine chemicals
Chemicals which are made on a small scale in chemical labs.
Name 4 fine chemicals
- Drugs
- Flavourings
- Preservatives
- Fragrance
What 6 things do chemists have to do when developing a new chemical product?
- Research catalysts for new processes
- Follow standard procedures
- Carry out a titration
- Scale up production
- Interpret results
- Carry out quality assurance
Why does the government have laws and regulations on chemicals? (2)
- To protect people; workers, customers and the populace in general
- To protect the environment from permanent or unsustainable damage
What are the 7 stages of chemical synthesis?
- Choosing a reaction
- Risk assessment
- Working out quantities
- Carrying out reaction in optimum conditions
- Separating the products and handling by product disposal/ use
- Purifying the product
- Measuring yield and chemical the purity of the product.
What 7 criteria do the sustainability of a chemical process rely on?
- Atom economy
- The use of renewable feedstock
- Energy inputs and outputs
- Health and safety risks
- Waste prevention
- Environmental impact
- Social and economic benefits
What is the formula to calculate atom economy?
Mass of atoms in the useful product / total mass of products x100
What is the formula for percentage yield?
Actual Yield (What you get) / Theoretical Yield (What you should get) x100
Social benefits of Green chemistry: (3)
- Cleaner air quality
- Cleaner buildings
- Improved water quality in rivers & lakes
Economic benefit of Green chemistry:
•reduced energy costs
How are Catalysts useful? (3)
They:
•Reduce the activation energy so the reaction can happen at a lower temperature and pressure
•Can improve atom economy
•Are not used up so make processes more sustainable
What are the optimum conditions for Enzyme Catalysts to work?
pH: about 7.4
Temperature of 37 Degrees centigrade
Bulk chemicals
Chemicals make on a large scale at an industrial level.
Name the 3 main properties of Alkanes:
- They have single covalent bonds and are saturated hydrocarbons
- They don’t react with water because the bonds are strong and unreactive
- The burn in air to produce Carbon Dioxide and Water
What is the general formula for Alkanes?
CnH2n+2
What are the names and formulas of the first 4 Alkanes?
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
How is the test for a double bond carried out? (2)
- Add bromine water
2. The alkene will become colourless because of the double bond
What are the bonds of Alkenes like?
- They have reactive C=C double bonds
* They are Unsaturated
What is the general formula for Alkenes?
CnH2n
What is the general formula for Alcohols?
Cn H2n+1 OH
Name the first four alcohols:
Methanol CH3OH
Ethanol C2H5OH
Propanol C3H7OH
Butanol C4H9OH
Name 2 uses of Methanol
- As a chemical feedstock
* In the manufacture of cosmetics
Name 3 uses of Ethanol
- As a chemical feedstock
- Solvent
- Fuel
What are the properties of Shorter chain alcohols:(3)
- Low boiling points
- Weak intermolecular forces
- Very soluble in water
What are the properties of Longer chain alcohols:(3)
- High boiling points
- Strong intermolecular forces
- Less soluble (float on top of water)
What are the products of the reaction between Alcohols and Sodium?
Salt and Hydrogen Gas (H2)
How does sodium react with alcohol, water and Alkanes?
- Sodium sinks in alcohols, doesn’t melt and slowly gives off hydrogen gas
- Sodium floats on water, melt, rushes around on the surface and rapidly give off hydrogen
- There is no reaction between sodium and Alkanes
Name the 3 ways Ethanol is produced?
- Synthesis
- Fermentation
- Biotechnology
What is the formula of ethanol production by synthesis?
Ethene + Steam -> Ethanol
C2H4(g) + H2O(g) -> C2H5OH(g)
What are the steps of Ethanol Synthesis? (6)
- Crude oil undergoes fractional distillation
- Long chain hydrocarbons (Alkanes) are vaporised and then cracks using a catalyst and heat
- The molecules are purified using fractional distillation
- The Ethene that is produced can be used as a feedstock and the remaining water is removed
- Ethene is reacted with steam at a high temperature and pressure with a catalyst to product ethanol
- Any unreacted products are recycled
What are the 3 steps of producing ethanol by fermentation?
- Water and yeast are mixed with natural sugars at just above room temperature.
- Enzymes found in the yeast catalyse the formation of ethanol and carbon dioxide.
- The carbon dioxide is allowed to escape from the reaction vessel but air is prevented from entering it.
What is the formula for Ethanol Fermentation?
C6H12O6(aq) -> 2C2H5OH(aq) + 2CO2(g)
What limits the concentration of ethanol when the fermentation method is used? (2)
- The amount of sugar in the mixture
* The fact that above a certain concentration the ethanol kills the yeast
What is done after the fermentation process to increase the concentration?
Distillation
What chemical products is the distillation process used to make?
Spirits like Brandy and Whisky
What happens if the optimum conditions for fermentation aren’t reached? (3)
- If the temperature is too high the enzymes become denatured
- If the pH changes too much the enzymes will also become denatured
- If oxygen is present, the ethanol is oxidised to form ethanoic acid (vinegar)
How is ethanol produced using biotechnology? (2)
- Ethanol is produced using genetically modified E. Coli bacteria and waste biomass
- The bacteria have had new genes introduced which allow them to digest all the sugars in the biomass and convert them to ethanol
What are the optimum conditions of the formation of ethanol using Biotechnology? (2)
- 25-37 degrees Centigrade
* pH of about 7.4
What are the first 4 carboxylic acids called and what are their formulae?
Methanoic Acid HCOOH
Ethanoic Acid CH3COOH
Propanoic Acid C2H5COOH
Butanoic Acid C3H7COOH
What’s the difference between strong and weak acids? (2)
Strong acids have a high concentration of hydrogen ions and are fully ionised whereas weak ones have a lower concentration of hydrogen ions and are partly ionised.
What are the properties of Carboxylic acids? (2)
- They are weak acids with high pH levels for acids (like 3-6)
- They are less reactive than strong acids
What are the word equations of the reactions of acids with Metal, Alkali, Carbonate and Hydroxide? (4)
Acid + Metal -> Salt + Hydrogen
Acid + Alkali -> Salt + Water
Acid + Carbonate -> Salt + Water + Carbon Dioxide
Acid + Hydroxide (base) -> Salt + Water
What is the reaction to make esters and what type of catalyst is used?
Carboxylic acid + Alcohol-> Ester + Water
•There is a strong acid catalyst present (e.g. Sulphuric acid)
How are esters named?
First half from alcohol and second half from the Carboxylic acid e.g Ethyl Methanoate (Methanoic acid + Ethanol)
Name 4 bulk chemicals?
- Ammonia
- Sulphuric Acid
- Sodium Hydroxide
- Phosphoric Acid
What is the main property of esters and their main uses? (1,4)
- They have distinct smells that are responsible for the smells and flavours of fruit
- They are found in: food products, perfumes, solvent and plasticisers
What are the properties of saturated fats and give an example of one:
- They have single Carbon-Carbon bonds
- The molecules are unreactive
E.g Animal Fats (Lard & fatty meats)
What are the properties of unsaturated fats and give an example of one:
- The contain double Carbon=Carbon bonds
- The molecules at more reactive than Saturated fats
E.g Vegetable oils (Olive oil, Sunflower oil etc)
How is the experiment to make esters carried out? (6)
- Add the acid, alcohol and strong acid catalyst and anti bumping granules (to prevent it from over boiling) to a pear shaped flask.
- Using a Bunsen burner reflux it over a Bunsen burner.
- Heat to the boiling point of the ester and using a reflux condenser, separate the ester gas by heating and condensing and transfer to a separating funnel.
- Add sodium carbonate to quench (neutralise) the Strong acid catalyst and shake. Open tap and run off the aqueous layer.
- Transfer to a volumetric flask, add anhydrous calcium chloride to remove the water.
- Then filter off and you’re left with a pure ester.
What happens during an exothermic reaction? Give an example (2,1)
- Energy is released as heat so it feels hotter after
- Energy is lost to the surroundings so the products have less energy than the reactants did
E.G Combustion
What happens during an endothermic reaction? (2)
- Energy is taken in so it feels cold to the touch
* Energy is taken in from the surroundings so the products have more energy than the reactants.
TRY TO REMEMBER THIS! Bond making and breaking!
Breaking bonds is endothermic and making them is exothermic
REMEMBER THIS! Endothermic and exothermic reactions!
Endothermic: more energy absorbed to break the bonds than is released when new bonds are made.
Exothermic: more energy released when bonds are made than was absorbed to break the old bonds.
How is equilibrium reached?
When the forward reaction and the backward reaction remain the same rate equilibrium is reached when the reaction stops.
How is dynamic equilibrium reached?
When the forward and backward reactions happen at the same rate and time so the concentration doesn’t change.
What is eutrophication? (5)
The process where nutrients leaches into water, cause algae to grow which block the light from going under the water’s surface, killing plants, letting bacteria which use all the oxygen eat them and therefore killing fish too.
What is an advantage of nitrogen fixation?
Since the nitrogen fixing bacteria make special enzymes that allow them to product nitrogen from the air, producing copies of these enzymes would make it possible to make fertilisers at room temperature and pressure.
What’s the issue with nitrogen fixation?
It doesn’t produce enough nitrates to grow sufficient food to feed the world.
What are 2 pros of organic fertiliser?
- long lasting
* less likely to be washed away
The downside of using organic fertilisers only?
There aren’t enough resources to make enough fertiliser to grow enough food for the world population.
What are the equations for the Haber Process?
Nitrogen + Hydrogen -> Ammonia
N2(g) + 3H2(g) -> 2NH3(g)
Give 4 uses for Ammonia:
Explosives, fertilisers, dyes and medicines
About what percentage of Ammonia gas is made by the Haber Process because of its reversibility?
15-30%
What are the compromises made for the Haber Process to be economically viable? (2)
- The pressure is a compromise between cost and yield
* The temperature is a compromise between rate of reaction and yield
What are the standard procedures for the collection storage and preparation of samples for analysis? (3)
- Collect multiple samples at random
- Store them in a clean and sterile container to prevent change, contamination or deterioration
- Label, sealed and store the container in a safe place
What is the mobile phase in chromatography?
A solvent that is either aqueous or non aqueous
What is the stationary phase in chromatography?
The medium that the solvent moves through (e.g paper)
The substance that is the … soluble in the mobile phase will be carried … through the stationary phase
The substance that is the most soluble in the mobile phase will be carried fastest through the stationary phase
What are the stages of paper chromatography?
- If the substance to be analysed is a solid, dissolve it in the suitable solvent
- Place a spot of the sample on a sheet of chromatography paper and the pencil line and allow it to dry
- Place the bottom edge of the paper into a suitable solvent
- As the solvent rises up the paper, it dissolves the sample and carries it up the paper.
- The different chemicals desperate because their molecules have different sizes and properties.
What makes up the stationary phase in thin layer chromatography (TLC)?
A thin layer of absorbent material (like silica) supported on a flat unreactive surface (glass plate)
What are the advantages of TLC? (4)
- Faster runs
- More even movement of the mobile phase up the stationary phase
- Choice of different absorbencies for the stationary phase
- Better separation for wider range of substances and ease of analysis
What are the two types of locating agents used on chromatograms to make clear samples appear?
- Fluorescent materials can be added and them they can be viewed under UV light
- Chemicals that react to produce colour can be sprayed on them (e.g ninhydrin)
What is the formulae to calculate the Rf value of a sample?
Distance travelled by solute (middle of sample spot) /Distance travelled by solvent
What are the mobile and stationary phases in gas chromatography (GC)?
Mobile phase = A carrier Gas
Stationary phase = A microscopic layer of liquid on an unreactive solid support
What are the advantages of GC? (3)
- Greater separating power
- The ability to separate complex mixtures
- The ability to produce quantitative data from very small samples of liquids, gases and volatile gases
What are some uses of GC? (2)
- Detecting banned substances in blood samples
* Analysing oil spills to identify sources of pollution
What is the unit used for concentration?
g/dm3
How is a standard solution made? (6)
- Weigh out 5g of solid sample in a beaker
- Dissolve in about 20cm3 of distilled water, add more of it doesn’t dissolve.
- Transfer to a volumetric flask using a short stem filter. Wash the funnel and beaker using distilled water and pour the washings into the flask.
- Add distilled water to the flask until it’s about 3/4 full and shake ‘til dissolved.
- Place the flask on a level surface and fill with water until the meniscus reaches the 100cm3 mark.
- Invert the flask to mix and ensure an even concentration.
What is the equation to calculate the concentration?
Concentration (g/dm3) = mass (g) / volume (dm3)
What are the steps of titration?
- Collect about 100cm3 of acid in a clean beaker, using a pipette and filler measure out 25cm3 and empty into a conical flask.
- Add indicator, swirl and place on a white tile.
- Make sure burette tap is closed and pour some alkali into the burette and wash. Then clamp the burette over the conical flask and fill it.
- Open the tap and run the solution into the flask, swirling to mix. As you near the w d point reduce flow to drops.
- Record the reading once the colour change has occurred and record the volume of alkali added.
- Repeat until you have 3 concordat values or repeat 3 times and take the average.
HERE’S HOW TO WORK OUT THE CERTAINTY:
- Use the range (difference between highest and lowest data value)
- Percentage error = Uncertainty / Average x100
- Certainty = 100 - Percentage error
- You write it as Certainty +/- Percentage error
What are systematic errors?
•Repeat measurements that are all incorrect by the same amount
What are random errors?
•All repeats have different incorrect values
