C7 Flashcards
What are the basic raw materials of the chemical industry?
- crude oil, air water, vegatable materials, rocks and minerals such as metal ores, salt, limestone and gypsum
What is the first step in any chemical process?
- converting raw materials into purified feedstocks
What is a general process for any chemical process?
- use enrgy or water to prepare raw materials to become feedstocks
- complete a chemical reaction using a catalyst
- possibly uses the energy produced by the reaction
- recycle any unchanged reactions and repeat the process
5 seperate and purify products from by products and waste
What are the products of the chemical industry?
- Basic organic: chlorine,sodium,hydroxide,sulfuric acid, fertilisers- bulk chemicals
- Petrochemicals and polymers
- fuels and products like polymers
- dyes , paints and pigments - Pharmaceuticals
- drugs, medicines - Specialty chemicals
- food flavourings, liquid crystal chemicals in falt screen displays
How has the chemcial industry tried to make a ne feedstock?
- DuPont- ferments renewable plant material
- makes polymers(Sorona) by converting the fermented plant material into fibres- for clothing
- plant material fermented with bacteruia= malonic acid
- Negatives: biomass issues
- land
- needs fertilisers
- needs energy to transport and harvest material
How do you calculate percentage yield?
percentage yield=actual yield divided by theoretical yield
e.g. Calcium carbonate = calcium oxide + carbon dioxide
calcium carbonate= 40+12+(16 times 3)= 100
calcium oxide = 40 +16= 56
theoretical yield= 56g.
actual yield = 48g.
48 divided by 56 times 100 = 85.7%
What is the equation for atom economy?
atom economy= mass of atoms in product divided by mass of atoms in the reactants
times 100
eg.calcium oxide=- 56
calcium carbonate =100
56 divided by 100 times 100 = 56%
What is an example pf the chemical industry implenting one of its aims?
- remove toxic health hazards
- replace toxic chemicals with non- toxic ones
- Monsanto used hydrogen cyanide in weedkiller
- hydrogen cyanide- removed from the process
How is energy generally used in the manufacturing of chemical products?
- to raise the temperature of the reactants so a reaction begins or continues
- to haet a mixture of liquids to seperatew and purify products by distillation
- to dry productsts
- to process waste
How is the industry trying to become more efficient?
- prevent loses of steam in leaking valves or stem pipes by installin insulation
- using the energy from exothermic reactions to generate electric power to contribute to the income of the process
- using catalyst eg. enzymes
- lower the temperature of some reaction
- less energy
- limit being denatured
How is waste reduced in the chemical industry?
- high atom enconomy
- increased recycling
- find uses for by- products
What is closed loop recycling?
- waste material is collected and used to manufacture the same product
What is open loop recycling?
this is where waste is collected and used to manufacture another yet lower quality product
How is harmful waste dealt with by the chemical industry?
- filtered, distilled, centrifuged
- netralised with acids and alkalis
- broken down with microorganisms
What are alkanes and what are their properties?
- fuel- gas - petrol
- Phsical properties
- insoluble in water
- 4carbon= gas
- 4-17 carbons=liquid
17 or more = solid
Chemical
- burn, falmmable
- strong covalent bonds
- do not react with acids or alkalis
What are alkenes?
What is a sturated and unsaturated hydro carbon?
- Alkane- not very reactive
- saturated
Alkenes- unsaturated
- double carbo bind
- increases reactivity of a molecule as it can add more hydrogen than alkanes
eg. plastic and polymers made from ethene
What are alcohols used for ?
- drink- beer , wine
- as asolvent
- used in cosmetic lotion+perfumes
- feddstocks
- adhesives, foams and wind screen fluid
Wgat is the structure and physical properties of alcohols?
- liquid at room temperature
- boiling point is less than water
What are the chemical properties of alcohols?
- highly flammable
- fuels
- reacts with sodium similary to water as
- oH
- in reactions only the hydrogen in the oh reacts while the other hydrogens are unreactive
What are the three ways ethanol acn be produced?
- fermentation
- biotechnology
- chemical synthesis
How is ethanol made from plants?
- some parts of the plant fermented
- Cellulose polymers extracted and heated with acid to break it down into glucose
– glucose= ethanol + carbon dioxide
- lower concentration
of ethanol 14 to 15 %
- can be distilled to increase concentration to 40-50%
Which stages require energy during the production odf ethanol?
- producing fertilisers for plants to grow
- transporting the feedstocks to the factory
- processing the feedstocks
- transporting the ethanol to its point of use
What are the three different energy balances from the feedstocks used to make ethanol?
-sugar cane 8.3-10.2 sugar cane can only br grown in tropical and subtropical climates used in Brazil
sugar beet 1.4- 2.1 used in UK
coen 1.3-1.6 used in US
How can ethanol be produced with biotecnology?
- modifying bacteria so they can breakdown a wide range of sugar
sugar= ethanol + carbon dioxde
- optimun temp. 25-37 and 6-7 pH
How can ethanol be produced using chemical synthesis?
- feedstocks ethene -produced by creating ethane from natral gas
- not renewable
- at 300 celcius 60 to 70 times atmospheric pressure
ethene +steam= ethanol
- atom economy =100%
– yet a side reaction produces polyethene
- yield 95%
How is the ethanol purified from chemical synthesis?
- 96% ethanol 4% water
placed on zeotites- special; compound with tiny holes in it
- water molecules go through ethanol left behind
What is the structure and names of organic acids?
-carboxylic acids
How is vinegar made?
ehtanol is oxidised to produce ethanoic acid or vinegar
What is the difference between strong and weak acids?
pH1-strong acids- nitric acid
- ionise completely when it dissolves
- pH3 - weak acids - carboxylic acid
only a small part of the molecules
ionises eg. + photo
- both acids react in the expected with metals, alkalis and metal carbonates
How are esters formed?
- chemists react an alcohol with a carboxylic acid to make an ester and water
What are the stages to making an ester?
- Heating under reflux
- the alcohol and carboxylic acid are combined with sulfuric acid and heated under reflux - Distillation
the mixture is distilled after reflux
- Purification
Then an aqueous reagent is added to removw impurities from the ester
Shake it
4.Drying
granules of calcium are added to the mixture
- impurities to the surface
5. Distillation
the mixture is distilled again to increase the purity of the ester
What are esters used for?
- plasticiers
- in perfumes/ cosmetics
- food/flavourings
What are alcohols and carboxylic acids in fats and oils?
- Alcohol is glycerol
- compound with three OH gruops
- carboxylic acids - long hydrocarbons attached to a carboxylic acid
What are saturated and unsaturated fats?
- Animals fats solid at room temperature
- vegatble oils are usually liquid
- Animsl fat
- Eg. stearic acid
- only single bonds
- saturated
- straight molecules
- tightly packed
- maxium amount of hydrogen in the molecule
- solid and strong intermolecular forces
Oils +photo
- eg. aleic acid
- double bond in molecule
- can get more hydrogen
- unsaturated
- not straight
- waeker intermolecular forces
- a liquid
How is soap made from fats and oils?
ester + water = acid + alcohol
- called hydrolysis
- slow change
- strong alkali- sodium hydroxide a good catalyst
for the hydrolysis of fats and oils by heating with alkali produces soaps
What is an exothermic reaction?
- respiratin, combustion
- give out heat or energy
What is an endothermic reaction?
- photosynthesis
- takes in heat or energy
What is an energy change calculation?
eg. h-h=434kj
o-o=498kj
o-h=464
What is activation enegy?
the point at which bonds break between atoms, so the process can occur
- the higher the activation energy the more difficult it is to get a reaction started
- catalyst reduce the activation energy
as they speed up reactions without adding any weight to the products
What is a reversible reaction?
-ice into water can water into ice
-
How can heating change a reaction?
gives atoms more energy to make collisions
eg. haeting decomposes blue copper sulfate crystals to give water and anlylrous copper sulfate, which is a white
Add water to the white powder after cooling it changes back into its hydrated form
As it does it turns blue again and gets very hot
How does concentration affect reactions?
-eg.
left to right = forward
right to left = backward
- forward
concentration of steam is high and the concentration of hydrogen is low
- Backward
the concentration of hydrogen is high and the concentration of steam is low
What is equilibrium in a reversible reaction?
- the point where the reaction has ceased
and the amount both sides of the reaction = eachother
How is equilibrium reached?
eg. iodine is souble in a potassium iodide solution in water
- the aqueous solution of potassium iodide is yellowish brown
- iodine is also soluble in organic solvents(hexane) in which it forms a violet solution. Aqueous potassium iodide and the organic solvent don’t mix+photo
- start the experiment, with a test tube with a small crystal of iodine in hexane
- add potassium iodide
- no colour change as the iodide is dissolved in the hexane
- shake once
- iodide goes yellow and hxane goes purple
- shake twice - violet- hxane
- yellowish brown - iodide
+photo Graph 1
+photo formula
- experiment can be repeated wiht the iodide being dissolved in the iodide first, the hexane added and the result is the same
- a reversible reaction
What does the experiment tell us about equilibrium?
- at equilibrium the concentration of reactamts and products do not change
- An equilibrium state can be approached from either the reactant side or the product side of the reaction
What is dynamic equilibrium/
- this is where the rate of forward reaction is equal to the rate of backward reaction
What are the uses of ammonia?
- fertilisers
- textiles and explosives
How is ammonia produced?
- using the Harber process
- reversible reaction between nitrogen and hydrogen gas
1. reactants compressed to about 200 times atmospheric pressure - haeted to about 450 celcius and passed over an iron catalyst
- 100%
- 15% yield
- process needs to be economical without using too much energy
+photo of the process
How does pressure affect the Harber process?
- increased pressure, increases production of ammonia but this means less hydrogen + nitrogen is recycled
How does temperature affect the Harber process?
the higher the temperature the less ammonia and more nitrogen and hydrogen mixture increases
How is nitrogen gas fixed?
- nitrogen fixed by bacteria in the roots of plants
What is the problem with the production of ammonia?
- requires 1% of all the energy in the world
- even though the energy consumption reduced dramatically
ver the last few years
What is a renewable way of producing hydrogen?
- electrolysis of wter
- relies on electricity, which could come from renewable resources
How could the Haber process be made more efficient?
- find catalysts with high catalytic activity
- in 2000 new catalyst found for Harber process 2.5 times more catalytic than before
- also could look at how ammonia is made in nature and mimic that process
- ammonis could be made at room temperature and at normal pressure
What is the first in an analytical method?
- pick method
- qualitive or quantitive
How is analysis performed?
- sample- that represents the bulk of the chemical is taken
- take multiple samples and measure masses or volumes
- samples are often dissolved in solution
- measure property of the sample
eg. acid, how much alkali is required to netralise it - Convert measurments into chemica quantitieseg. calculate the amount of an acid by knowing the amount of an alkali it takes to netralise it
- Lastly analyst state their confidence in the results, and compare repeats
How big to samples have to be?
- sample has to be representative of the whole thing
1. Scientists have to decide when analysing samples how many samples and the amount of each to take - how many repeats, they should do
- where wnd when to collect the samples
- how to store and take them to the lab
What is a hetrogeneous and homomgeneous sample?
- homogeneous
- bottle water
- all the same in the bottle
- hetrogeneous
- water from a stream
- different at different points
What are some types of chromatography?
- cheap
- paper chromatography, requires pape+ solvent
- expensive
- gas chromatography
- high precision instruments
What are the principles of chromatography?
- seperate and identify the chemicals in a mixture
- check the purity of a chemical
- purify small samples of a chemical
How is paper chromatography done?
- Paper chromatography
- mobile phase= solvent
- small amounts of the substances are applied to the paper
- solvent moves up the paper and the chemicals move
- each chemical has a dynamic equilibrium
eg. distribution of molecules between the paer and the solvent - if the chemical is more attracted to the mobile phase, moves faster, yet if more attracted to the stationary phase more slower
- chemicals seperate
What are the advantages and disadvantages to paper and thin layer chromatography(TLC)?
- Dis
- limited use
ad
quik, cheaps
- requires only small volumes of solutions
- good pre- experiment test
What are aqueous solutions and non-aqueous solutions?
- -aqueous - solution in water
- non-aqueous- solutions with no water
What is the mobile and stationary phases TLC and is TLC down?
- mobile phase-solvent
- stationaryp hase- an absorbent
solid supported on a glass plate or stiff plastic sheet
- sample dissolved in solvent
- applied to stationary phase
- allowed to dry then more solution is added if dilute
- sample analysed
What is a chromatogram?
- add substance to solvent
- put solvent in a chromatography tank and put a lid over it
- after a few minutes put a prepared paer( maked with a base line and spotted)or TLC
- all over the paper, but only above the baseline - solvent rises up the paer, leaving a sustance that can be analysed
How are colourless sustances located on paper or TLC?
- develop chromatogram by spraying it with a locating agent that rea ts with substances to form coloured compounds
- Use on ultraviolet lamp with TLC
plate that contains flurescers, so that tha spots appear violet in UV LIGHT
How can chromatograms be interpreted?
- comparing spots with those from standard reference material
- retardation factor(Rf)
Rf= distance moved by chemical divided by distance moved by solvent
What are the advantages and disadvantages of Gas chromatography?(GC)
- better than paper or TLC
- more sensitive
- can measure amounts of each chemical present
- yet expensive
- lots of high value equipmwnt
What is the process of GC?
mobile phase: carrier gas(helium0
stationary phase: thin film of a liquid on the surface of powdered soil, packed into a sealed tube column
- some compound carried move slowly than others
as they have different boiling points or greater attraction to the stationary phase
- very small smaples needed
How is the sustances seperated and detected in GC?
- right temperature= carrier gas being turned on
- pressure adjust to get correct flow
- sample injected just before column enters the oven
- sample becomes a gas and mixes with carrier gas
- chemicals identified using mixture of known composition
How are GC chromatograms interpreted?
- detector sends signal to a recorder/computer
when compound appears
- each peak one compound
- position of each peak is a record of how long the compound took to pass through the column- the retention time
- height of the peak tells the amont of the compound
Why are titrations done?
- quick, convenient, accurate and easy to automate
How are titrations performed?
- analyst used pipette(or burette) to transfer a fixed volume of liquid to a flask
eg. acid base titration- might be 20cm(3) of the acid solution to measured volume
2. add two drops of indicator
3. indicator turns sharply green - end point
How are solution accurately prepared?
solution of sodium carbonate
- accurately weigh the sodium carbonate
- dissolve it in a small amount of solvent
- tranfer the solution to a graduated flask
- Rinse al the solution into the flask with more solvent
- add solvent drop by drop to make up the volume to the mark on the flak
- put a stopper on the flask and shake the flask
How do chemists show uncertainty in results?
98%
98 + or - 0.2%
What are mistakes?
- actions that can lead to outliers in results
- not using a senesitive mass balance
What are the two types of uncertainty/
-systemic errors and randomn errors
se
-pipette in 25cm(3) grade (+ or -0.06)
rs
-meniscus is aligned slightly differently when solutio are measured
a randomn error means the same measurment repeated several times gives different values
-judgement about colours of a solution
systemic errors means that the same measurment repeated several times gives values that are cosistanly higher or lower than their true value
eg. incorrectly calibrated equipment
What are sources for uncertainty in a titration?
- meniscus
- size of volumetric flask may vary
- burette may be calibrated incorrectly
- difficult to make exact judgement of the end points of a titration
- mass balance will show measurements to only a certain number of decimal points
What is accuracy and what is precision?
- Accuracy describes how close this result is to the true or actual value
- Precision is a measure of the spread of measured values. A big spread indicates a greater uncertainty
than a small spread
What are the two parts of a scientific conclusion?
- Valid means that the techniques and procedures used were suitable for what was being analysed or tested
- Justifiable means that conclusions reached are based by sound, reliable evidence
