Further Chemistry Flashcards
What are bulk chemicals?
Chemicals produced on a large scale, eg ammonia, sulfuric acid.
What are fine chemicals?
Chemicals produced in much smaller quantities, eg pharmaceuticals (drugs), food additives, fragrances.
What do chemists do in the chemical industry?
They work to research and develop new chemical products and processes.
Why are there laws to regulate the chemical industry?
To ensure people’s safety; to reduce impacts on the environment; to ensure safe storage and safe transport of chemicals.
What are the reactants called in an industrial process?
The feedstocks.
What is the process of making the chemical?
Synthesis.
What are sustainable processes?
Sustainable processes use renewable feedstocks and do not damage the environment at any stage of the process.
What needs to be done with the products at the end of the process?
They need to be separated from waste and by-products.
How would purity of the product be maintained?
By regular checks.
A sustainable process will consider these factors…
use renewable feedstocks; finding other uses for by-products and waste; energy input, outputs and use of renewable energy; reducing the environmental impact of the process; Ensuring the health and safety of people; Social and economic benefits for people.
If a reaction has high atom economy it produces less?
waste.
If the reaction uses all the atoms the process has …… atom economy?
100%
What is atom economy?
The percentage mass of the atoms used in the final product.
An exothermic reaction gives out….
heat.
An endothermic reaction takes in…..
heat.
In an ……. reaction, reactants lose energy as they form products.
exothermic
In an ……. reaction, reactants gain energy as they form products.
endothermic
Energy levels can be shown on what type of diagram?
Energy level diagram.
What does activation energy look like on an energy level diagram?
A steep peak, with an arrow underneath.
What is the activation energy?
The minimum amount of energy needed to start the reaction.
What is the activation energy needed for?
To break the bonds to start a reaction.
If the activation energy is high, how would this affect the number of molecules that have the required energy?
There would be very few.
If the activation energy is low, how would this affect the number of molecules that have the required energy?
There would be many more molecules than when the activation energy is high.
What can be said about the rate of reaction of reactions with a high activation energy versus rate of reaction of reactions with a low activation energy?
Low activation energy reactions will usually be faster
If an exothermic reaction has very high activation energy, what might happen at room temperature?
Nothing, as there is not enough energy (eg, hydrogen and oxygen)
What would happen to a mixture of hydrogen and oxygen if you provided the initial activation energy by a spark, or heat?
It would react, violently, as the energy given out by the first reaction is enough to give activation energy to other molecules.
What do catalysts do to the rate of reactions?
Speed it up.
What happens to the catalyst as the reaction happens?
Nothing, it is not used up.
Why do industrial processes use catalysts?
So the product can be made faster
Is a catalyst specific to one reaction?
No, one catalyst can work for different reactions.
What is the name for a biological catalyst?
An enzyme.
What are enzymes made of?
Protein.
Where are enzymes found?
In living cells.
Is an enzyme specific to one reaction?
Usually, yes.
How do catalysts and enzymes speed up reactions?
They provide an alternate route for the reaction.
What does a catalyst do to the activation energy of a reaction?
It lowers it.
If the activation energy is lower, what does this do to the number of reactant molecules that have the required energy?
It goes up.
Which works across a broader range of conditions, enzymes or catalysts?
Catalysts
Why must industrial processes that use enzymes be tightly controlled?
Enzymes are very sensitive to reaction conditions, eg pH, temperature.
Some reactions with high atom rate economy are too slow to be used in industry. How can this be helped?
Use a catalyst or enzyme.
What does a catalyst or enzyme speeding up a high atom economy reaction in industry enable?
Use of the process to increase the sustainability of the industrial process.
What does use of catalysts or enzymes mean for the reaction temperature? What is the implication for energy use by the industrial process?
Reaction temperature is lower, saving energy and costs.
What happens to an enzyme when the reaction conditions are wrong?
It is denatured.
What does denatured mean when applied to a protein?
The shape changes.
What happens if the shape of an enzyme changes?
It can no longer work as it is the wrong shape to bind to the reacting molecules.
What happens to bonds in a chemical reaction?
They are broken and formed.
If the energy given out when bonds are made is greater than the energy required to break the bonds then the reaction is?
Exothermic
If the energy given out when bonds are made is less than the energy required to break the bonds then the reaction is?
Endothermic
What is the activation energy needed for?
To break bonds.
Why do different reactions have different activation energies?
Different bonds need to be broken.
Given the bond energies for the reaction, how would you work out the energy change change?
Add up the bond energies for the bonds that are made, subtract those that are broken. (Remember that you might break/make the same bond more than once)
What is the word equation for bond energy change?
Energy given out = energy given out making bonds - energy taken in breaking bonds.
Where would you find the relative atomic mass?
Periodic table
Which number is it?
The bigger one, mass includes the neutrons so has to be more than the proton number!
What is the relative formula mass (RFM)?
The relative mass of a molecule (Or formula unit).
How would you work out the relative formula mass?
Add together the relative atomic mass for each atom.
How can relative masses be use to work out actual masses?
They give the ratios in the equation, and you can therefore calculate the actual masses if you have one actual mass.
What is a hydrocarbon?
A compound containing hydrogen and carbon only. Nothing else, not even at Christmas.
What do hydrocarbons make when they burn in air?
Carbon dioxide and water.
Are alkanes soluble in water?
Not usually
Do alkanes react with aqueous substances?
Not usually
What is the bond energy of the H-H and C-H bond in alkanes like?
High, bonds are difficult to break. (Think how close the H nucleus is to the shared electron pair)
How reactive are the alkanes, generally, other than burning?
They are not reactive.
What must you do to get alkanes to start burning at room temperature?
Add activation energy.
What do saturated molecules have that makes them saturated?
Only single bonds between 2 carbons.
What do unsaturated molecules have that makes them unsaturated?
One or more double bonds between 2 carbons.
What is the general formula for an alkane?
CnH(2n+2) (remember the carbons at the end each need an extra hydrogen)
What is the general formula for an alkene?
CnH(2n)
What is the family of compounds that look like an alkane with an -OH?
Alcohols
Compare the solubility of alkanes and alcohols in water?
Alkanes are not soluble, alcohols are
What is the melting/boiling point of an alcohol compared with the alkane with the same length carbon chain?
It is higher.
How does ethanol react with sodium?
The sodium fizzes as hydrogen is made.
Give the equation for the reaction of sodium and ethanol
2Na(s) + 2C2H5OH(l) => 2C2H5ONa + H2
In the reaction between sodium and ethanol, what group reacts with the sodium?
The -OH group.
Name the alkane with 1 carbon.
methane
Name the alkane with 2 carbons.
ethane
Name the alkane with 3 carbons
propane
Name the alkane with 4 carbons
butane
Why does ethanol react with sodium when ethane doesn’t?
The -OH group is the part that reacts with sodium
What is the process of making alcohol from sugar using yeast?
Fermentation
What is the word equation for fermentation?
sugar => ethanol + carbon dioxide.
Why does fermentation stop when the solution of alcohol becomes less dilute?
The alcohol is toxic to the yeast.
How does the yeast ferment the sugar?
It uses enzymes.
Why must the conditions for fermentation be right?
The enzymes that the yeast uses need a narrow temperature range, and a pH of about 5 is optimum.
What happens if the pH or temperature for fermentation are wrong?
Fermentation slows down, or stops.
How would you make a dilute solution of ethanol more concentrated?
Distillation.
How can you distil ethanol?
Heat to just above the boiling point of ethanol (78C), which will boil the ethanol; collect the ethanol vapour and cool it. This will be more concentrated alcohol,and is called a “spirit”.
When is distillation used?
To make ethanol for fuel and spirit drinks.
What is required to distil ethanol?
Large amounts of energy
What is the impact of using lots of energy for distillation
It has an impact on cost of processing and the environment.
What is the usual raw material to the fermentation process?
Plants grown as crops.
What are the problems of using plants as the input to the fermentation process?
The plants contain only small amounts of sugar, so large amounts of unused plant material are produced as waste.
Why are we trying to use waste materials from crop production as biomass to input to the fermentation process?
Using waste from agriculture would improve sustainability.
How can we ferment waste biomass from agriculture?
Genetically modified bacteria.
What can the genetically modified bacteria do?
Digest cellulose (plant cell walls) and produce ethanol.
What has to be done to the biomass?
It has to be dissolved in acids and solvents.
Why is the use of genetically modified bacteria to produce alcohol not being done commercially?
It does not yet work well enough.
Where would you find ethane as input to an industrial process?
Crude oil.
How could you make ethanol from ethane?
First, turn ethane into ethene, then make ethanol using ethene and steam. Catalyst required
Give the equation for turning ethane into ethene
C2H6 => C2H4 + H2
Give the equation for turning ethene into ethanol
C2H4 + H2O => C2H5OH
What are the advantages and disadvantages of making ethanol from crude oil?
Crude oil is not renewable; high temperature required so lots of energy needed; high atom economy as only hydrogen produced; hydrogen is a very useful by-product; faster than fermentation
What are carboxylic acids?
An alkane with a COOH group.
What do carboxylic acids taste like?
Sharp, unpleasant.
What do carboxylic acids smell like?
The smell of rancid butter and sweaty socks are both caused by carboxylic acids.
What can the COOH group produce in solution, that makes it an acid?
The H+ ion
Which acid is found in some plant and insect stings?
Methanoic acid.
Which acid does vinegar contain?
Ethanoic
What is the chemistry of the carboxylic acids?
They are typical (weak) acids.
What does carboxylic acid + metal give?
salt + hydrogen.
What does carboxylic acid + alkali give?
salt + water
What does carboxylic acid + carbonate give?
salt + water + carbon dioxide.
What is the ending given to all the salts of carboxylic acids?
-oate (eg ethanoate, methanoate)
Are carboxylic acids strong or weak?
Weak
Why is vinegar safe to use when it contain ethanoic acid?
Ethanoic acid is a weak acid, and it is very dilute.
Name some strong acids?
Nitric, sulfuric, hydrochloric
What is the pH of a strong acid?
Very low
What is the pH of a weak acid?
Low, but nearer to 7
What makes a strong acid strong?
It produces more H+ ions when dissolved in a specified volume of water.
What can be said about the ability of strong acids to ionise?
They ionise completely, ie all molecules split into ions when they dissolve into water.
What can be said about the ability of weak acids to ionise?
Most of the molecules do not ionise, they remain as complete molecules.
Which acids are most reactive?
Strong acids.
Which acids react more slowly?
Weak acids.
How would you use magnesium to tell the difference between a strong and a weak acid. Describe your observations.
Place the same amount of magnesium in each, both would fizz, but the one in the strong acid would fizz more. If you time which one uses up the magnesium first that would be an objective way of telling the strong acid as the strong acid will react more quickly.
What do esters smell of?
They have fruity smells and flavours.
Why do esters taste like fruit?
It is natural esters that give fruit their flavours.
Why do ester smells travel easily?
Their low boiling points mean they evaporate quickly at room temperature.
What is ethyl ethanoate used as?
A nail varnish remover as it is a solvent, and it smells nicer than alternatives.
What are esters used as?
Plasticisers; fruity flavourings; fruity perfumes; solvents in eg inks
How would you make an ester?
React an alcohol with a carboxylic acid.
What is the advantage of synthetic esters over natural ones?
They are often cheaper.
How would you make ethyl ethanoate?
CH3COOH + C2H5OH => CH3COOC2H5 + H2O
The reaction to make ethyl ethanoate is slow. How would you speed it up?
Heat; catalyst (sulfuric or phosphoric acid)
Why would you heat 2 substances under reflux?
It is a way of heating substances with low boiling points without losing them
What happens when you heat under reflux?
You cool the pipe coming from the flask so that the vapours condense and run back into the flask.
What are the stages to making ethyl ethanoate?
Heating under reflux; distillation; purification using a tap funnel; drying.
What is a tap funnel?
A beaker with a tap underneath, as the layers of the mixture separate it is possible to run off each layer through the tap.
How would you remove the impurities when making ethyl ethanoate?
Remove excess ethanoic acid by adding sodium carbonate; the salt remains in the aqueous layer; then add calcium chloride to remove the ethanol, which will dissolve in the calcium chloride and water layer. The water layer will therefore contain the impurities that can be easily removed with the tap funnel.
How would you dry ethyl ethanoate?
Add anhydrous calcium chloride, then filter the calcium chloride out.
What does anhydrous mean?
Without water, used on salts that usually contain water of crystallisation.
How would you know that you had pure ethyl ethanoate?
It would boil at 77C. If not, you might need to distil again.
What is the state of a fat at room temperature?
Solid.
What is the state of an oil at room temperature?
Liquid
What do living things use fats for?
Energy
Where do we usually get fats?
Animals
Where do we usually get oils?
Plants
How do we make fat and oils?
Using fatty acids and glycerol.
What organic group do fats belong to?
Esters
What are fatty acids?
Carboxylic acids with very long carbon chains.
What is glycerol?
A tri-alcohol, it has 3 -OH groups.
What sort of fats are most animal fats?
Saturated
What sort of fats are most vegetable oils?
Unsaturated.
How are some carbons joined in an unsaturated hydrocarbon chain?
Double bond
How could you test for unsaturation?
An unsaturated compound turns orange-brown bromine water colourless. (Works on alkane v alkene as well)
What are reversible reactions?
Reactions that can happen in both the forward and backwards directions.
What can reversible reactions reach?
An equilibrium where the amount of reaction each way is exactly matched.
What do you need to reach an equilibrium in a reversible reaction?
A closed system where none of the reactants or products can escape.
Why is it called a “dynamic equilibrium”?
Because the reactions are still taking place.
Why do we need synthetic fertilisers?
Plants need nitrogen for growth, cannot take it from the air, and there is not enough in the ground to support taking crops year after year.
What is synthetic fertiliser often made from?
Ammonia
what is the formula for ammonia?
NH3
How is ammonia made in industry?
Using the Haber process
What are the feedstocks for the Haber process?
Nitrogen from the air and hydrogen.
What is the reaction for the Haber process?
N2 + 3H2 2NH3 (can’t do a real reversible reaction sign)
How is the Haber reaction prevented from going backwards?
The ammonia is removed.
What would be the yield if the ammonia were not removed?
About 20%
What are the conditions for the Haber process in industry?
Pressure of 200atm; temp 450C; iron catalyst
What would raising the temperature do?
Increase the rate of the backwards reaction, so reduce the yield; increases fuel required
What would raising the pressure do?
Increases rate of reaction and yield; increases the risk of leaks; more expensive to maintain
How are organic fertilisers made?
Waste materials from animals and plants
How are synthetic fertilisers made?
In the chemical industry, from feedstocks in an industrial process.
Why is there a lesser problem with run off into waterways if you use organic fertiliser?
They are usually less soluble in water.
Why is it a problem if fertilisers get into the ponds etc?
Algae grow; algae dies; bacteria party and use the oxygen; fish and other organisms die from lack of oxygen; double bacteria party until only anaerobes remain
How do nitrogen fixing bacteria fix the nitrogen from the air?
Enzymes.
Why would it be better if we could imitate the natural nitrogen fixing processes?
More economical; less run off.
Where do nitrogen fixing bacteria live?
In the soil; in some plant roots, eg clover, beans, peas
How could you use genetic engineering to help with the problems caused by run off?
GM crops could be engineered to fix their own nitrogen, or to have the nodules needed for nitrogen fixing bacteria to live in their roots.
Why are processes that rely on bacteria more sustainable?
They do not use as much energy; they do not depend on non-renewable resources
Why are we not producing fertiliser using bacteria?
Still experimental, does not work well enough for large scale use yet
Why is the Haber process not sustainable?
Uses methane (natural gas) to make hydrogen, not sustainable; high energy for temperature/pressure; high energy for transport ; large amounts of water used; high CO2 production due to the high energy use.
What is qualitative data?
Data about what is in the substance.
What is quantitative data?
Data about how much of each substance is in the sample
Why are measurements on each sample of chemical repeated?
So that outliers can be identified before the data is processed.
What is done at each stage of the chemical analysis?
The process is standardised so that the data will be comparable.
How would you choose a sample of a chemical?
You would choose a sample that is representative.
How can the person testing the chemical make sure that they do not introduce contamination?
Wear gloves and masks; making sure that equipment to collect the sample is clean; make sure that there are no chemicals present that could contaminate the sample (eg acid in paper)
Why would you need to store chemical samples carefully?
So that they do not deteriorate before testing.
How would you store a sample that contains bacteria?
In the fridge, to slow down their breeding
Why can some samples not be stored in a freezer?
Plant and animal cells are damaged by the ice crystals that form.
Why are some samples stored under an inert gas?
To stop oxidation.
Why would some samples need very dry conditions?
To stop reaction with water vapour.
What is chromatography?
A method of analysis for some mixtures.
What 2 things does chromatography use?
Stationary phase and mobile phase.
What is the stationary phase in chromatography?
The bit that does not move, eg the paper
What is the mobile phase in chromatography?
The bit that moves and carries the other substances along.
What is an aqueous solution?
A solution in water
What is a non-aqueous solution?
A solution in a solvent other than water
Why would using different solvent give different patterns?
Different solvents spread the substances out differently; the substances will be differently soluble in each solvent.
What is the substance dissolved in a solution called?
The solute
What would you call two solvents which do not mix?
Immiscible
What happens if you add a solute to a beaker containing two immiscible solvents?
If the solute is soluble in both, it will dissolve in both to varying degrees, an equilibrium will be reached between the two solutions.
How does chromatography work?
The substrate that dissolves most in the solute will be carried furthest.
What is the stationary phase in paper chromatography?
The paper
What is the stationary phase in thin layer chromatography (TLC)?
A plate of paper or glass coated with a thin layer of solid eg silica
Where would you put the sample in TLC?
A spot is put on the plate, on a pencil line, high enough for the spot not to be under the layer of solvent when the end of the plate is put into the solvent.
How long should the plate with the sample stay in the solvent in TLC?
It should be removed before the solvent reaches the top of the plate.
How would you use TLC to identify the substances?
You would compare against reference samples, comparing distances travelled.
How would you “find” substances that are not coloured in TLC?
Use a locating agent.
What could a locating agent be?
eg UV light, or iodine
What is the R1 value in TLC?
R1 value = distance moved by sample/ distance moved by sample.
Why use R1 values in chromatography?
R1 values are always the same for a particular substance in a specific solvent at the same temperature.
What would happen to the R1 value if you change solvent?
It would change, as the solubility of a substance is different in different solvents.
What is the stationary phase in gas chromatography?
A solid, which is packed into a coiled column so that it takes up less space.
What is the mobile phase in gas chromatography?
A carrier gas.
What surrounds the column (stationary phase) in gas chromatography?
An oven.
What information does the gas chromatograph give?
A printout of times taken through the column by the various substances.
What is the time taken to travel through the gas chromatograph called?
Retention time.
What would a mass spectrometer attached to a gas chromatograph give you?
The mass of the substance to help identify it.
What is a standard solution?
A solution of known concentration, a known amount of solute in a known amount of solution.
What gives the best estimate of the true value of a set of results?
The mean.
What does the range of results give you?
An idea of the uncertainty in the accuracy of the results.
What are outliers?
Measurements that do not fit with the others, probably errors.
What is quantitative analysis?
Analysis that involves taking measurements of quantities.
How would you make a standard solution?
Measure the mass of solute in a clean beaker. Dissolve in distilled water (stir). Pour into a volumetric flask (use a funnel). Rinse the beaker, stirrer, funnel with distilled water. (important step in the exam - to make sure no solute escapes). add more distilled water to the volumetric flask until you reach the correct level. Invert the flask (the book does not say, but I would use a stopper before this last stage).
For standard solutions, how do you measure concentration?
g/dm^3
How do you convert from cm^3 to dm^3?
Divide by 1000
What is the equation for concentration?
Concentration (g/dm^3) = mass of solute (g) / volume of solution (dm^3)
How do you do an acid/base titration?
Measure out a known amount of base (use a pipette), add a few drops of indicator, place on white tile to help with seeing colour change, put acid in burette, add acid to the beaker from burette, swirling beaker each time. When the indicator changes colour permanently record the end point. Take the first reading as rough!
How many repeats of titration should you do?
At least 3.
How close should your results be for an acid base titration?
Within 0.1cm^3
What causes errors in acid base titrations?
Drips from pipette, not filling pipette accurately; splashes or spills; missing the colour change; adding acid too quickly; misreading the burette.
To do the calculation, you need the….
the equation and the relative formula mass.
