Chem Analysis and Using Recourses Flashcards
Pure substances
- single element/ compound with no mixed substances
- to see if pure they should boil at exact boiling point (eg, water at 100)
Formulations
- mixture designed for a useful product
- carefully measure quantities for desired properties
Examples of formulations
- fuels
- cleaning agents
- paints
- medicines
- alloys
- fertilisers
- food
Chromatography definition
- the separation of mixtures that gives information to indentify substances
Rf =
Distance moved by substance / distance moved by solvent
Mobile and stationary phase
- molecules can move (liquid/ gas) and they are molecules with higher solubility and less attraction to the paper
- molecules that can’t move (thick liquid/ solid)
How to test for pure substances with chromatography
- pure sample run it along the tested and if Rf value is = the tested is pure
Tests for gases
- hydrogen, burning splint held at open end of tube makes ‘squeaky pop’ sound
- oxygen, relights a glowing splint
- Carbon Dioxide, passed through limewater it turns cloudy
- chlorine, damp litmus paper bleaches
Flame tests reasons
To identify cations
Results of the flame test
- lithium, crimson-red
- sodium, yellow
- calcium, orange- red
- potassium, lilac
- copper, green
Reasons for metal hydroxide precipitate test
To identify cations
Precipitate test results
- Calcium, White
- copper, blue
- Iron (II), green
- Iron (III), brown
- Aluminium, White -> colourless
- magnesium, white
Carbonates reaction
- react with dilute acid to form CO2 gas
Halide reactions
- produce precipitates with silver nitrate in dilute acid
- silver chloride, white
- silver bromide, cream
- silver iodide, yellow
Instrumental methods + advantages
- how compounds detected
- sensitive (detect small amounts), fast, accurate
Flame emission spectroscopy
- example of instrumental method
- metal ions analysis
- put through and light travels through spectroscope
- output line identifies ion and can measure conc
Proportion of gases in the atmosphere
- 80% nitrogen
- 20% oxygen
- small properties of CO2, water vapour and noble gases
Evolution of the atmosphere
- started 4.6 billion years ago, Early on there was intense volcanic activity that released gases plus water vapour
– atmosphere mostly CO2, water vapour condenses to form oceans. Volcanoes also produce nitrogen
– the oceans dissolved CO2 in water and carbonate will precipitated producing sediments reducing CO2 in yet
How Oxygen increase during evolution
– Algae first produce oxygen through photosynthesis plus plants produced more
– as they involved oxygen levels slowlt increase alone evolution of animals
Greenhouse gases
– Maintain temperature high
– include methane, water vapour, CO2
– allow short wavelengths from sun but absorb longer wavelengths from earth
Reasons for climate change
– Scientist believe it is from human activity
– but, difficult to model complex systems at least to simplified models and speculation
Consequences of climate change
– Polar caps melting leading to rise of sea levels
– change of rainfall patterns
– increase severity of storms
– amount of water changes
Carbon footprint
Total amount of CO2 or other greenhouse gases emitted in lifecycle of a product
Ways to reduce carbon footprint
– Renewable energy
– tax emissions
– cap emissions
– calturw CO2
Why the reduction of carbon footprint is difficult
– Tax Impax economy
– not everyone on board
– change lifestyles
What are atmospheric pollutants
– Combustion of fuels (coal, carbon, hydrogen)
– incomplete combustion (soot)
Properties of Atmospheric Pollutants
– Carbon monoxide replaces O2 in humans
– sukphur dioxide creates respiration problems
– acid rain from sulphur dioxide kills plants
– particulates lead to global dimming and health problems
Sustainable development
– We use the earths resources for warmth, shelter, food, transport
– natural resources are supplemented by agriculture
– finite resources from, earth ,ocean, atmosphere
Does chemistry allow sustainability and needs for future generations
Potable water
Water thats treated for humans to drink but not pure
Methods to produce post for water
– From freshwater is passed through a mash then three sand/gravel is a filter solids
– sterilisation is used to kill harmful microbes
Desalinisation of water
– Use membranes (reverse osmosis)
– the water passes through membranes that sort his tracks
– but needs a lot of energy and it cost a lot
Distilling water required practical
– Test pH with pH meter
– test for sodium ions (still) with flame test and test for chlorine few drops of nitric acid plus silver nitrate to form white precipitative
– to distil pour salt water in apparatus and water evaporates and then condenses
– the test if it is pure PH should be 7
Stages of waste water treatment
– Screening, removing large materials
– sedimentation in a tank, heavy objects sink
– effluent removed and treated book through aerobic digestions, the airbrakes down the matter
– the slides releases methane gas used for energy for fertilisation
– the waste water with toxic substances use UV light or membranes
Alternative methods of extracting metals (copper is finite)
– Bioleaching, uses bacteria to produce leachate solutions that contain metal pole compounds
– phytomining, plants absorb metal compounds plants harvested and burnt to produce ash that contains it
Problems with these alternative methods
– Extracting requires a lot of energy plus fossil feuls
Life-cycle assessment
– Raw materials that can damage the local environment
– manufacturing plus packaging, energy plus pollution produce
– uses of the products (burning)
– product disposal, landfill plus energy use for transport
Comparing life-cycle assessments
– Plastic bag uses crude oil, fractional distillation, it is reused, recyclable but not biodegradable
– timber, process with a lot of energy, are usually used once, biodegradable but non-toxic and recycled
Problems with LCAs
- Effects of pollutants hard to give value
– could be biased in order to support claims of companies
Reducing the use of resources
– Recycling plus reuse
– glass can be crushed or melted to produce other products
What is corrosion?
– Destruction of materials by chemical reactions (rusting with Air water)
How to prevent corrosion?
– Painting/coating with plastic
– electroplating (electrolysis)
– oil/creases for moving parts
– galvanising (spraying with zinc)
Alloys
– Most metals today
– gold measured by carrots
– high carbon steel (strong but brittle), low carbon steel (easily shaped)
Ceramics
– Clay ceramics shaped by wet clay and heat in furnace
Composites
– Fibreglass, low density, high strength
– carbon fibre, light, strong
– concrete buildings
– wood
Properties of polymers (ceramics, polymers)
– Low density poly (ethene) moderate temp under high-pressure plus catalyst (bags)
– high density poly (E 15) at low temperature in low pressure with different catalyst more rigid
Two types of polymers
– Thermo softening, individual chains with weak forces
– thermosetting, monomers from cross links and solid structure and don’t soften when heated
Stages of the haber process (nitrogen plus hydrogen goes to ammonia)
– Hydrogen and nitrogen ratio 3 to 1
– put it into a reaction vessel with iron catalyst, 450°C, 200 ATM
– condenser for liquid ammonia
– unuse H/N recycled
compromises for the haber process
– For a max yield plus speed
– increase pressure means more ammonia produce but it costs a lot of money and is dangerous
– iron catalyst increases speed
NPK fertilisers
– Compounds of nitrogen, phosphorus, potassium to increase the growth of plants and the yield
How to obtain Nitrogen, Potassium and Phosphorus
- nitrogen from ammonia
– Potassium obtained by mining
– phosphate rock can not be directly used as a fertiliser in brackets treated
Ammonia in industry
– giant Vats, increased concentration, exothermic
– he evaporates water to produce concentrated ammonium nitrate
Ammonia in the lab
- Small-scale titration or crystallisation
– current lower concentration which is safer
– ammonium nitrate crystals are formed
– slower process than the industry
