(fill in equations) Purple in Bold: Key information. Green: Equations, definitions and Scientists. Random Knowledge/ Later Topics

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1 RED: write syllabus dot point on other side in red. (with question that you make up in blue for flash cards) and one word heading on this side in red. Random Knowledge/ Later Topics Isomer: Same chemical formula, but different structure. Eg. 2-Methylpropane (C4H10) Butane (C4H10) Purple in Bold: Key information Green: Equations, definitions and Scientists (fill in equations) Allotrope: Same element but different physical form/properties (graphite, and diamond) IUPAC naming: 1 st. Find stem (longest chain); (name meth- etc). 2 nd Identify bond type (-ene. etc). 3 rd Add branch group (yl if necessary). 4 th Add other elements & write in alphabetical order and lowest no. s or give lowest no. to the most electronegative element.

2 Word and Balanced Formulae Equations Note: Alkane CnH2n+2 INCLUDE STATES! Alkene CnH2n Complete combustion of ethane (in plentiful supply of Oxygen) Incomplete combustion of ethane (in limited supply of Oxygen) Sulfuric acid plus magnesium hydroxide (note: balance protons in H and in hydroxide) Fossil Fuels provide both energy and raw materials. Fossil Fuels are a non-renewable (used at a greater rate than they can be produced and therefore can t be replaced) energy source formed by fossilisation of a once living organism that is now used to produce energy. (eg. Crude oil, natural gas, coal, coke, petroleum) Energy in fossil fuels originates from the Sun, as solar energy is converted to chemical energy by photosynthesis. Renewable fuels can be replaced eg. Ethanol (but cant be reused) tides, hydroelectricity. Natural gas is composed of 75-90% methane, ethane (5-10%), propane and butane (3-6%) and is a mixture (can be separated physically, various MP and BP etc.) Structural Formulae and Carbon Compounds IUPAC Naming Fossil Fuels are carbon-based. Hydrocarbons: organic compounds only containing C and H atoms. Homologous Series: a group of compounds with similar structure and chemical properties. (eg. Alkane, Alkene and Alkyne) Functional Group: grouping of atoms that is common to all members of that series. (e.g single bond (-ane), double bond (-ene). Prefixes: C1 meth- C2 eth- C3 prop- C4 but- C5 pent- C6 hex- C7 hept- C8 oct- Saturated Carbon Compound: contain only single bonds (alkanes) Unsaturated Carbon Compound: contain double and/or triple bonds. Carbon atoms are numbered so that the carbon with a triple or double bond has the lowest number possible. Carbon can form many compounds because it has 4 valence electrons which can form strong covalent bonds. It can form chains and rings, it can form covalent bonds with non-metals and halides can replace H s. (don t need to know yne or yl branches) Refining of Petroleum Petroleum is separated by fractional distillation (different boiling points). Crude oil, is a mixture of linear, branched, cyclic hydrocarbons, aromatic carbon compounds and other elements and compounds. Crude oil is used for energy, and also the source for the building blocks which we get plastics and synthetic fibres. One includes ethene. Crude oil is separated by cracking and Fractionation. Fractionation heats crude oil in a column that is cooler at the top than the bottom so that the smaller lighter chains which condense at lower temperatures (low BP) are separated at the top, while the longer, heavier chains which condense at high temperatures (high BP) are separated at the bottom.

3 Natural gas is often found with Crude oil, and both are formed by heat and pressure acting on buried plant, and animal matter (single-celled marine organisms) for long periods of time. The gas is trapped beneath impervious layers of rock. Petroleum consists of crude oil and natural gas, and is a mixture. The products of fractional distillation of Petroleum (crude oil) include Diesel, Petrol, Petroleum Gases, Kerosene, Oils and greases.

4 Source of Ethylene from Cracking (C2H4) - Ethene (systematic name)/ Ethylene (common name) is produced by: Catalytic Cracking of some of the larger molecule fractions from petroleum refining. (fractional distillation) The larger molecules are passed over a heated catalyst that cracks the larger molecules into smaller molecules. Catalysts adsorb (adhere to the surface) the reactants, therefore weakening their bonds and reducing the activation energy for the cracking reaction. Zeolites are a naturally occurring group of substances containing a mixture of aluminium and silicon oxides. Eg Al2O3. Zeolite catalysts (with a large surface area) are often used as the catalyst for cracking. A major by-product of catalytic cracking is ethene. Thermal Cracking (steam cracking) is where ethane and propane from natural gas deposits are mixed with steam and passed through very hot metal coils. The heat from the coils breaks some C-H and C-C bonds to convert ethane and propane into ethene. Due to high temp s needed this process is very expensive, therefore the catalyst development was an important advancement Ethylene is Readily transformed into useful products. Due to Ethylene s double bond it has a high reactivity and can be transformed into many useful products. The C=C double bond can be opened to allow new chemicals or chains to be added. Alkenes are therefore more reactive than Alkanes. This is shown when bromine water discolours quickly when in contact with an Alkene but not with an Alkane. Product Formula Uses Ethanol Ethanoic acid 1,2-ethanediol Disinfectant, solvent, renewable fuel. Preservative 1,2 dibromoethane Petrol additive Polyethylene (common polymer) Polystyrene (common polymer) PVC (common polymer) Antifreeze, photographic film Food wrap, bottles (cheapest plastic) CD cases, Styrofoam Raincoats, piping, kitchen utensils.

5 PRACTICAL Compare reactivity of Alkanes and Alkenes Note 1: bromine water (brown/yellow): Bromine is non-polar but the full valence electrons in the diatomic bromine (halogen therefore diatomic) means the H s on the water have a slight attraction to the electrons making it have extremely low solubility. 2: Cyclohexene is C 6 H 10 and cyclohexane is C 6 H 12 (two less H spots due to circle). 3: Use cyclohexene as liquid and less volatile. (meth, eth, prop, but are gases) Alkenes are unsaturated hydrocarbons that react readily by the process of addition. Alkanes are saturated hydrocarbons that react slowly (or not at all) by the process of substitution. Aim: compare reactivity of alkenes and alkanes with bromine water. Method: 1. Transfer 1mL of bromine water into two small test tubes. 2. Add ONE drop of cyclohexene to first test tube, and flick. If no obvious colour change repeat to a maximum of 5 drops, and record observations. 3.Repeat for cyclohexane, and record observations. 4. Place test tube rack in UV light for several days. Observe changes. (don t need to know step 4 for syllabus) PRACTICAL Compare reactivity of Alkanes and Alkenes Results: -Cyclohexene: 3 drops added decolourised from yellow to clear. -Cyclohexane: 5 drops added no colour change but due to bromine being nonpolar it physically moved to dissolve into cyclohexane (not a chemical reaction). - In UV radiation Bromine and cyclohexane slowly reacted due by substitution. (some bonds were broken from the UV) Conclusion: Due to cyclohexene s double bond making it unsaturated it reacted in the presence of Bromine water. The double bond opens up and reacts with the Bromine to form 1,2 dibromocyclohexane. The cyclohexane didn t react with the bromine water as it has a single bond and is saturated, but slowly reacted when in UV light. Risk Assessment Risk Bromine water is corrosive and harmful. Precaution Handle with care, avoid skin contact and put in chemical waste when disposing of. Response Clean spills up immediently, and wash off skin with water.

6 Ethylene (Monomer) can be polymerised to Polyethylene (Polymer) Increased Pressure: such as increased temperature, or compression creates more collisions of the molecules with the container walls. High Pressure: -causes the monomers to link quickly to haphazardly form multi-branched chains with low molecular masses (terminates quicker). -This branching prevents chains from aligning closely, making Low Density PolyEthylene (LDPE). The far apart aligning also makes very weak dispersion forces between the chains creating soft and flexible polymers. (LDPE is used in clingwrap and ziplock bags etc.) Addition Polymerisation of Ethylene Note: keep edges of monomer s free when drawing. Note: if R on end of molecule it means rest of molecule. Note: always draw at least 3 monomers Low Pressure: -Allows the monomers to carefully link up producing more linear chains with higher molecular masses. -This means close alignment of the chains can occur creating High Density PolyEthylene (HDPE). The close alignment and heavier mass creates increased dispersion forces and therefore harder, less flexible polymers. (HDPE is used for plastic bottles and food containers)

7 Polyethylene- Addition Polymer Polyethylene is an addition polymer which forms when monomers add together to form polymers and no other product is produced. In addition polymerisation all monomers have a C=C bond. This can react to create an active centre, which constantly moves on until typically two active centres meet on another (termination). (chain reaction) Addition polymerisation is used to make polyethylene, polystyrene, Polyvinylchloride (PVC) and polypropylene (banknotes) Steps in production of Polyethylene. 2 forms of Polyethylene can be manufactured depending on conditions. o LDPE (High gas pressure) an initiator of organic peroxide is used (not a catalyst). o HDPE (low gas ressures) an initiator of catalyst Ziegler-Natta is used, which is a complex metallic compound that helps create long unbranched, ordered polymers. Free-radical polymerisation is an example of addition polymerisation. Free Radical: particle with un-bonded electron Steps in production of Polyethylene. Steps: Crude oil - fractional distillation - Catalytic or Thermal Cracking of larger molecules to produce ethylene - addition polymerisation of ethylene (such as free-radical polymerisation). Free-radical polymerisation Steps: Initiation (START) -Generate a free radical species (species with a single unbonded electron). -Free radicals are formed by breaking chemical bonds (usually by heat) so that the bond ends up on the two separate fragments. -Initiator examples include Organic Peroxide, Benzoyl Peroxide (BPO) and Ziegler-Natta. Propagation (CONTINUE) -Radical derived from initiation grabs another electron from convenient source eg. a C=C bond will open to leave a single bond with radical and also regenerate a radical centre (active site).

8 Steps in production of Polyethylene. Propagation (CONTINUE) -The new radical centre looks for other double bonds, and the active site continues to move along as the chain reaction occurs and the chain lengthens. Termination (STOP) -The initiation usually generates radicals in pairs, and there are lots of initiator molecules in the reaction. -Each initiator will be propagating chains, and when one chain runs into another, they will combine to generate a new bond, terminating the process. -Occasionally in High pressure, chains will link around to themselves. -Termination occurs faster in higher pressures. -Small polymers are created by adding lots of initiators. (Terminates faster) -Larger polymers are created by adding minimal initiators. (Terminates slower) Note: no matter what initiator is used, or the length, or whether it s linear or has branches, they are all called the same. (Polyethylene etc.) Commercially significant monomers names, properties and uses. Monomers Polymers Common Systematic Name Name Properties Used for Name Ethylene Ethene LDPE - Low density polyethylene Low density, soft, flexible, strong, water resistant. Vinyl chloride Chloroethene HDPE- high density polyethylene -Polychloroethene -Polyvinlychloride (PVC) High density, hard, strong, water resistant. Water resistant, flame resistant Cling wrap, shopping bags, zip lock bags. Playground equipment, containers. Raincoats, water pipes, kitchen utensils Modelling Addition Polymerisation Advantages -This process is too small and fast. -The models are therefore useful, as they allow us to visualise (things we can t see too small and too fast) this process of monomers linking which is too small to see, and shows the dynamic nature which is too quick to see as well. -The molecular model kits also allow us to understanding the 3D nature of the process. Disadvantages -Represent an inaccurate scale. -Doesn t illustrate particle movement accurately -Wrong representation of bonding, creates misinterpretation that there is a physical link between atoms and no representation of intermolecular forces. -Non-3D models don t show 3D nature or all sides of molecule. -Simplifies complex processes. -Oversimplifies the details Some Scientists research the extraction of materials from biomass to reduce our dependence on fossil fuels. Biomass (organic matter produced by photosynthesis in plants) is a renewable resource. Biomass consists mostly of cellulose and can be used and the formed again by the input of solar energy during photosynthesis Need for alternative sources Petrochemicals are made from compounds in petroleum or natural gas. Over 95% of fossil fuel is burnt as energy source, and no longer available after being burnt. Less than 5% of fossil fuel is used to make polymers, and a tiny percentage is recycled.

9 Styrene Ethenylbenzene -Polyethenylbenzene -Polystryene Expanded polystyrene. (created trapped gas inside) Transparent, hard, strong Low density, good insulators. CD cases, tool handles. Body boards, insulated cups and esky s. Petrochemicals used as fuels create carbon (cause respiratory problems) and carbon monoxide (toxic). Plastics are non-biodegradable. Genetically modified crops is a possible solution, and improving methods of producing ethanol (fuel needed to create biomass) will reduce costs. Demand (increasing) > Supply from Petrochemicals (Decreasing)

10 /3 Condensation polymerisation Condensation polymerisation is a reaction between two monomer molecules have two characteristics: o They have functional groups such as (carboxylic acid group (-COOH), alcohol group (-OH) or amine group (-NH2). o Usually has at least two functional groups (reactive sites) A condensation polymer is formed by monomer molecules condensing out (eliminating) small molecules (water, ammonia etc.) and the two functional groups become linked. Therefore, in contrast to addition polymerisation; o TWO products are produced the polymer and the condensate (and for every monomer linked, there is one less condensate in total). o No double bonds Eg. - Glucose monomer molecules reach through two hydroxyl groups (- OH), a water molecule is condensed out, and the -O- links the monomers. - Produces either starch or cellulose plus water (no. of glucose molecules minus 1 is the total number of water molecules.) Cellulose contains basic carbon-chain structures The cellulose biopolymer contains a sequence of 6 carbons with hydrogen and hydroxyl groups attached. These hydroxyl groups can be replaced by other groups. This basic carbon-chain sections could be changed to chemicals that are to build petrochemicals. It would be quite useful if a process or micro-organism could break the glucose into chains of 2/3/4 Carbons. Therefore would be a renewable resource, and could be used instead of fossil fuels to make polymers Development of Biopolymer. (evaluation) Cellulose is a Condensation Polymer and Major Biomass component. Cellulose is a natural condensation polymer and is a major biomass component. Cellulose is derived from the monomer glucose, and water is eliminated. The bulky CH2OH groups, are on alternate sides of the units. These hydroxyl groups form hydrogen bonds with adjacent chains. These hydrogen bonds result in long strong cellulose fibres which is why wood is a strong material and dry plants consist of 50% cellulose. Therefore, the macromolecular structure of cellulose is insoluble in water and resistant to chemical attack. The hydroxyl groups on the outer surface of cellulose means water can adhere to it. (capillary action of water transport in plants) Biomass fuels cost more than fossil fuels due to complicated conversion process, and creates deforestation of the natural environment Development of Biopolymer. (enzyme) In 1960s a company used specially-bred strains of bacteria that were grown in fermentation vats and fed on glucose (waste from sugar mills) The bacteria (eg. Bacillus magaterium) produced polyhydroxybutyrate (PHB) which was used as a form of energy storage. Polyhydroxybutyrate is insoluble in water, permeable to O 2, resistant to UV light, High MP, high tensile strength, denser than water, non-toxic, biocompatible, biodegradable. BUT was too brittle. Propanoic acid was added to the bacteria s diet which they then produced a more flexible co-polymer (consists of two monomers). Systematic name is: Polyhydroxybutyrate-hydroxyvalerate or P(HB-HV) The polymer is then isolated and purified.

11 Biopol is a commercially produced biopolymer that is biocompatible, biodegradable and renewable. It is used in medical applications where there are no fossil fuel alternatives, and can be used in multiple applications (disposable rubbish bags, nappies) The use of transgenic plants is expected to lower costs to make this polymer more price competitive with traditional petroleum-produced polymers. Recently genetic engineering of inserting genes into E. coli bacteria. Means that E.coli can now produce PHA more efficiently (grow faster etc.) Or inserting genes into plants (potatoes) to produce PHA rather than storing starch, again making a cheaper process. A wider range of cheaper food sources (containing glucose) have now also been used to grow the bacteria. (eg. agricultural wastes)

12 Development of Biopolymer (summary) Co-Biopolymer (Bacteria s diet is propanoic acid and glucose): Polyhydroxybutyrate-hydroxyvalerate or P(HB-HV) Monomer: 3-hydroxybutyrate and 3-hydroxyvalerate Bacteria: Bacillus magaterium and genetically modified E. coli bacteria Enzymes responsible for the storage of energy 3-ketothiolase and acetoacetyl-coa and PHB synthase Evaluation: - in exam relate to eg. (shampoo container) Durable (practical), Flexible(squeezable), Slow aerobic degradation (won t degrade before finished with), Fast anaerobic degradation (many landfills are anaerobic), expensive. Therefore if becomes cheaper, very effective and suitable choice PRACTICAL - Molecular model kits the addition of water to ethylene and dehydration of ethanol. Hydration (addition of water) to ethylene (remember dilute acid therefore ethene needs water) Dilute H 2SO 4 Ethene + water ethanol Dehydration of ethanol (remember concentrated acid steals water therefore dehydrates) Concentrated H 2SO Other resources, such as ethanol, are readily available from renewable resources such as plants. Chemists are searching to look to the chemicals in biomass for renewable sources of energy. As fossil fuel supplies are depleted, ethanol obtained from renewable plant resources will become more important Identify the IUPAC nomenclature for straight chained alkonols Often referred to as Systematic naming. Alkanol CnH2n+1OH or CnH2n+2O The presence of the OH substituted for a hydrogen, and is indicated by the suffix ol. Indicate which carbon has the OH with a number. (use the smallest no.) Numbers and letters are linked with a hyphen. Eg. 2-propanol Numbers are separated by a comma. Eg. 1,2-ethanediol Eg. CH3CH2CHOHCH2CH2CH3-3-hexanol Eg. CH3CH2CH2CH2CH2CHOHCH2CH3-3-octanol /4 Dehydration of ethanol to ethylene (and need of catalyst) Addition of water to ethylene (and need of catalyst) Hydration of ethylene (addition of water) to produce ethanol is carried at a lower temperature (to favour exothermic, forward reaction). Dilute sulfuric acid (or dilute phosphoric acid) is used as a catalyst. The reaction has a high activation energy, so the catalyst provides an alternative, low-energy pathway. As the catalyst breaks the double bond, which water would not normally do (water is very polar, ethene is non-polar). Dehydration of ethanol (removal of water) to produce ethylene in school uses a concentrated sulfuric acid (180 C) as the catalyst. The reaction has a high activation energy and is endothermic, therefore the catalyst provides an alternative, low-energy pathway and absorbs

13 Ethanol water + ethene the water formed to stop the reversing of the reaction. The high temperature favours the forward reaction In industry porous ceramic catalysts are used.

14 Many uses of Ethanol Ethanol is bio-degradable, and bio-compatible, and renewable Ethanol makes ethylene, is a solvent, and is a fuel Many uses of Ethanol as a solvent for polar and non-polar substances The OH group is polar (hydrophilic) which helps it dissolve polar and ionic substances. The CH 3 CH 2 - chain is non-polar, (hydrophobic) and can dissolve non-polar molecules. Ethanol is used as a solvent in food colouring, and flavourings. Ethanol is also used to dissolve non-polar substances such as medicines that don t dissolve easily in water. Once the non-polar solute is dissolved in ethanol, water can be added. Ethanol is the second most important solvent (is non-polar and polar) and is the least toxic of all the alcohols. Note: look at polar question and answer in practise Q s Ethanol as a fuel and why it is a renewable resource. Ethanol readily combusts in air and is energy-dense. Due to the O atom in ethanol is almost always completely combusts. (little CO or O formed). Ethanol is a renewable resource as: o The rate that ethanol can be made from plant material is equal to or greater than the rate at which it is used up. o The Products of combustion, are the reactants needed by plants for photosynthesis, which produces glucose (the raw material used to create ethanol)

15 PRACTICAL Summarise use of Ethanol as an alternative car fuel. In Australia, up to 10% ethanol (E10) can be added to petrol (without causing damage) to extend our petroleum reserves. Ethanol is a suitable alternative car fuel as: o Similar physical properties to petroleum (density, volatility, ignition temperature etc) so minimal modifications are needed. o Relatively energy-dense (80% efficiency compared to petrol) o Similar waste products (no new pollution issues) o Readily biodegrades and photodegrades. (little impacts from spills) Ethanol was successful in sales (increased from 2005 to 2011) but when the subsidy of the Ethanol was removed it became a bit more expensive. So due to E10 being 8% less efficient but only 1.5% cheaper, the sales declined Assess potential of ethanol as an alternative fuel. Ethanol can be used as an alternative fuel in internal combustion engines if it can be: o Economically produced from renewable resources; or o Subsidised as a fuel to reduce air pollution and dependence on non-renewable resources Disadvantages of Using Ethanol Lower heat of combustion than petrol (less energy produced so cars travel less distance with same amount.) therefore more expensive. It is difficult to remove water during distillation of fermented biomass, which causes corrosion of engines. Thus, modified engines needed if >10% used. Land is needed to grow food crops to make ethanol, which results in deforestation. This is ecologically unacceptable. Ethanol needs to be distilled from fermentation mix, transported and harvested. Distillation needs lots of energy which is obtained by burning fossil fuels. This is expensive, and ecologically unacceptable.

16 Advantages of Using Ethanol Ethanol is produced by fermentation of biomass. This is a renewable source as plants can be grown to replace the ones used (biomass) and fermentation is carried out by fungi (yeast, E.coli). Burns more completely and cleanly. The O in ethanol ensures less oxygen is needed for complete combustion, meaning less CO and C is produced. Ethanol is also a good solvent, dissolving deposits built up in the engine. Carbon dioxide neutral. The f CO2 produced when ethanol burns = amount of CO2 used in photosynthesis by crops that are later converted into ethanol. 10% ethanol can be safely added to petrol without damage to engines. This extends petrol supplies Define molar heat of combustion and Ethanol s first-hand data value The molar heat of combustion (ΔHc) is the heat change when one mole of a substance is completely combusted to form products in their standard states at SLC (100 kpa and 25 C) Ethanol ΔHc = 1367 KJ/mol (given as positive value even though its exothermic) Graph: There is a linear trend between the heat of combustion values for the different alkanols as the subsequent members in the homologous series (additional C-C and two C-H bonds) per molecule (the larger the carbon chains) have more bonds needed to be broken during combustion, therefore release more energy. Differences between supplied and experimental data (bad validity) Heat loss to surroundings and lost from system (air and can) Incomplete combustion (evidence by soot on bottom of can). This means that not all of alkonal loss measurement was fully combusted. Some of fuel might have evaporated and not combusted. Suggestions of Improvements PRACTICAL Determine and compare heats of combustion of at least three liquid alkanols per gram and per mole. Look at study notes Aim: Determine and compare the heat of combustion values for methanol, 1- propanol, and 1-pentanol by measuring and processing calorimetry data. Risk Assessment Risk Precaution Response Methanol is toxic. Avoid Skin contact. Wash off straight away. Flammable liquids Have no loose clothing or Have experienced person put hair. Avoid spills. fire out with extinguisher. Method: 1. Obtain spirit burner with alcohol, record mass of burner+ alcohol 2. Transfer ml of water (100g) into metal can. 3. Assemble apparatus with can 2cm above burner. 4.Record initial temperature of water. 5. Ignite wick, Heat until water rises 20 C, blow out flame 6. stir water gently. Record highest temperature of water 7. Remove spirit burner and record final mass of burner+alcohol /10/11 Fermentation of glucose to ethanol equation, chemistry, and conditions. Ethanol obtained from fermentation of glucose or hydration of ethene. Fermentation metabolic anaerobic process by some micro-organisms (yeast or bacteria) which decomposes carbohydrates (usually glucose) to release energy. Ethanol and CO2 are wastes. Overall reaction: glucose yeast ethanol + Carbon Dioxide Carbohydrates are obtained from plants (breakdown of cellulose or starch, or directly from sugars).

17 Ensure initial water temp is almost air temp, and minimal appropriate distance between spirit burner flame and beaker (use can- conductor/thin). Insulate sides and top of can, to reduce heat loss to surroundings. Have plentiful oxygen supply. Ensure flame directly heats can by suspending it with a retort stand Yeast can digest starch/carbohydrates to glucose. Therefore, plant material s depend on region. (Eg: molasses left over from sugar cane factory may be used). Conditions (Promote fermentation): Suitable temperature (yeast C) Suitable ph (yeast 4-5 from phosphate salt) Suitable micro-organism (yeast) Water Escape for CO2 Small nutrients for yeast (phosphate salt) anaerobic

18 Once ethanol concentration reaches 14-15%, yeast can t survive, and fermentation stops. Rather than removing ethanol as it is produced, one technique to continue fermentation is to immobilise the yeast in a gel and allow the nutrient solution to flow over them PRACTICAL Carry out the fermentation of glucose and monitor mass changes. Fermentation is a vital process used in diverse industries (baking, brewing etc) Aim: Carry out the fermentation of glucose and monitor the changes in mass. Method: 1. Add 200mL distilled water to a 250mL conical flask. 2. Weigh glucose powder ( 10g). Add powder to flask and swirl to dissolve. 3. Add pinch of Na2HPO4 as a yeast nutrient. Mix thoroughly. 4. Add. 1g dried yeast, swirl into solution. Then stopper flask with cotton wool. 5.Record total mass of apparatus and place in warm, dark location (incubator) 6 Record total mass each day for 1 week. We loss mass due to CO2 escaping. Once no more CO2 loss this means that there is no more glucose for yeast to eat, so reaction stops. But some evaporation will occur (extra mass loss, and why we have a control), so ignore this in HSC Q s Summarise the processes involved in the industrial production of ethanol from sugar cane. Sugar Cane Or if using cane fibre from filtration turn it into a sugar Chopped and solution. Crushed ETHANOL Filtration Filtrate - sugar solution (Using glucose) Fermentation Ethanol Mixture Distillation CO 2 By-products and wastes Yeast or GM bacteria

19 9.2.4 Oxidation-reduction reactions are increasingly important as a source of energy. Reactions of metals need transfer of elections. Activity Series (most reactive is best electron donor.) /2 Relationship between displacement of metal ions in solution by other metals to relative activity. - When a more active metal atom is placed in a solution containing ions of a less active metal, the more active metal loses one or more electrons to become a cation and the electrons transfer to the ions of the less active metal, which becomes metal atoms and is displace from solution. Memory Aid: OIL Oxidation Is Loss (of electrons) RIG Reduction Is Gain (of electrons) Oxidation state increases Oxidation state decreases Although the oxidation and reduction reactions are written as two separate half-equations, they always occur together. You can t have one substance losing elections without another gaining electrons Changes in Oxidation State (charge on particle) When a substance acts as a reducing agent (reductant), causing reduction it gets oxidised. When a substance acts as an oxidising agent (oxidant), causing oxidation it gets reduced. Oxidation state of atoms of an element is zero. Eg. Cu is 0 Oxidation state of metal cation (M n+ ) is (+)n. When a metal oxidises (loss of n electrons) there is an increase in oxidation number from 0 to +n. When an ion or atom gains electron(s), there is a decrease in the oxidation number. (decrease=reduction) Calculate the potential E requirement of named electrochemical processes using tables of standard potentials and half-equations. The Table of Standard potentials is for SLC & concentration of 1mol.L -1. E value (standard electrochemical conditions) given is for the forward equation (reduction- from left to right, thus Oxidation from right to left). If you need the reverse process value, simple change the +/- sign.

20 A metal will displace the ions of any metal below it. For a redox reaction to occur without an external source of energy the overall reaction must have a positive E value /6/7 Explain Galvanic cells in terms of oxidation/reduction reactions. Construction of galvanic cells, direction of electron flow. Define anode, cathode, electrode and electrolyte to describe galvanic cells. A galvanic cell is a device constructed so that the reductant and oxidant are physically separated in two half cells and converts chemical energy into electrical energy which can turn a motor and produce heat. The larger the galvanic cell the more electrical energy can be obtained. Even though separated they are still connected by an external circuit made of a conductor (to carry electrons) and a salt bridge (carry ions in solution). As the electrons have to move through the external circuit from the oxidation half-cell (anode) through the conductor to the reduction half cell (cathode) which is electrical energy. Galvanic Cell IUPAC notation: -Single line represents boundary between phases (atom/ion). -Double vertical line represents salt bridge. Electrons flow from anode to cathode (a goes before c in alphabet) (an ox stand above a red cat) Anode (negative) is the electrode where oxidation occurs. (AN OX). CaThode (positive) is the electrode where reduction occurs (RED CAT) A solution containing ions is an electrolyte. Electricity (moving charge) can flow through electrolytes by charged ions, not electrons. Electricity flows in electrodes (metals or graphite) or connecting wires by the movement of electrons, not ions. Salt bridge (filter paper soaked in potassium nitrate, as K + and NO 3 - don t produce precipitates with any ions.) Positive and negative ions moving through the salt bridge keep a balance of negative and positive charge in each half-cell. Electron flow is opposite to anion to equalise charge. (KNOW ELECTRON DIRECTION)

21 /9 PRACTICALS Identify conditions under which galvanic cell is produced. And measure the difference in potential of different combinations of metals in an electrolyte solution. Aims: (Sentences above) Method: 1. Set up apparatus, close switch and if voltmeter reads below zero, reverse the connections (polarity). 2. Record the Voltage with Zn Zn 2+ Cu 2+ Cu. 3.Then repeat when: a) one electrode (anode or cathode) is removed from electrolyte. KNO 3 b) One wire is removed. c) The salt bridge is removed d) The Cu electrode sits in distilled water (use new salt bridge). 4. Repeat steps 1-2 for other combinations, using a new salt bridge each time. Results/Conclusions: Magnesium and Copper (0.70V) produced the greatest voltage as they are the two most separated standard potentials. Step 3 had no voltage produced, therefore the conditions needed for a galvanic cell is o Dissimilar electrodes in an electrolyte. o The electrons need to have a pathway (wire conductor) o The ions need a pathway (the salt bridge). Differences in experimental results and calculated values: o Could have been an oxidised layer on electrodes (thus contaminated) o Solutions might not have been exactly 1 molar concentration. o Ions might have contaminants in the solution. o Connections in electrical circuit might not be very good.

22 Structure and Chemistry of a dry cell and evaluate it in comparison to a button cell. In terms of: -chemistry -cost and practicality -impact on society -environmental impact Cell: single anode and cathode Battery: Several cells in series. Dry Cell: Electrolytes in form of solids or pastes. The Paste acts as a salt bridge and the electrolyte. Alkaline Dry Cell: The electrons flow from the zinc anode through the conductive wire which a dry cell is put in to the graphite cathode. Button Cell Mercury (II) Oxide Cost and Practicality Impact on Society Environmental Impact More expensive than original dry cell, but is cheaper, lighter, and has better performance and shelf life. Significant stimulated development of small, portable electrical devices. Eg. Toys, radios. Non-renewable resources used for components (mining). Zinc is a potential toxic metal, and rest goes to landfill. Disadvantages More expensive than original dry cell, but safer and better. More expensive than dry cell, but relatively cheap, very small and lightweight, and lasts long time. Development of VERY small electrical devices such as hearing aids, digital watches etc. Non-renewable resources (mining). Hg is a heavy metal contaminant is a very big issue. Hg disposal. HgO cells now replaced by Ag2O cells. Very dangerous if swallowed by children

23 9.2.5 Nuclear Chemistry provides a range of materials Stable and radioactive isotopes and unstable nucleus conditions Atomic Weight average of atomic masses of atom isotopes. Neutrons = A-Z Electrons = # protons Most isotopes are radioisotopes. Isotopes - have the same atomic number (protons) but different mass numbers (A), thus different number of neutrons. Every element has more than one isotope. Which are unstable and will undergo radioactive decay by emitting energy (in form of gamma radiation) and/or releasing particles (alpha or beta). The stability of a nucleus depends on the neutron:proton ratio (lighter nuclei = 1:1, heavier nuclei greater than 1:1) Nuclei like tennis balls (if repelled each other) and velcro balls that hold them together. The time it takes for the radioactivity level to be halved is called its half-life (t 1/2 ). Each radioisotope has its own characteristic half-life. Types of Radiation Radiation Type Description Alpha 4 2 He particle He nucleus Beta 0-1 e particle High-speed electron Gamma Electromagnetic radiation High frequency/high energy Types of Radioactive Decay Radioactive decay occurs when an unstable atom (parent isotope) decays to form a stable nucleus (daughter isotope). The type of radioactive decay depends on arrangement of protons and neutrons. Largest stable isotope is Lead atomic number 82. A nucleus is also more unstable if there is an odd number of protons or neutrons.

24 -decay: an particle (He nucleus with 2 protons and 2 neutrons) is emitted from the radioisotope nucleus. In most cases, -radiation is also emitted. (mass changes by 4, and charge changes by 2) -decay: A neutron will emit a negatively charged -particle (high-speed electron). The neutron now has a positive charge, so it has become a proton. Once again, -radiation is also emitted. (mass stays same, charge goes up one) Electron-capture: a proton combines with an electron to become a neutron. Positron-decay: a proton emits a positively-charged electron (called a positron) and becomes a neutron. Some large unstable nuclei spilt into two or three smaller daughter nuclei, with -rays, neutrons and other particles emitted. Either spontaneous nuclear fission or deliberately induced by bombarding an unstable nucleus with neutrons, then as the nuclei emits more neutrons it becomes self-sustaining nuclear chain. (uncontrolled nuclear weapon, controlled nuclear reactor) Identify instruments and processes that can detect radiation Photographic film darkens when exposed to radiation. Nuclear industry workers wear modified photographic film badges. It is modified by placing the photographic film behind plastic coating with differing layers of metallic shielding. This blocks most of the and but not the which creates a more detailed indication of the amount of radiation exposure. Geiger-Muller tube connected to a counter (a Geiger counter ) can detect ionising radiation (most radioactive emissions are high energy radiation that causes ionisation and is harmful). Two electrodes are separated by Inert gas. Ionising radiation passes in dislodges an electron (creating cation and free electron) from a gaseous atom (ionisation). The electron travels to opposite electrode, and creates a small pulse of electricity in circuit (used to generate a click). Some substances produce a flash of light (scintillation) when struck by radiation. A photomultiplier amplifies the light so it is recorded and counted in a Scintillation counter. (used for non-ionising radiation).

25 Describe how transuranic elements are produced. Transuranic elements have an atomic number above uranium (Z>92) and have undergone nuclear transformation. They are all man-made, radioactive and most have short half-lives. Production: 93, 94 and 95 have been produced in Nuclear Reactors when U-238 is bombarded with slow-moving neutrons (come from decay of Uranium) which may be absorbed creating a new unstable nucleus. Pu-239 is then changed to americium by neutron bombardment (twice) then -decay Process information from secondary sources to describe recent discoveries of elements Transuranic elements began to be produced in the 1940 s, methods of acceleration particles improved and so more elements could be discovered. The latest was in 2010 when Ununseptium was produced for the first time. Particle accelerator (cyclotron etc): From atomic number 96 and above, all are made by accelerating protons or small nuclei with a heavy nucleus target. By using alternating electric and magnetic fields high speeds are created to overcome electrostatic repulsion of the charged particles.

26 Describe how commercial radioisotopes are produced Neutron-rich radioisotopes are produced in nuclear reactor s and neutrondeficient radioisotopes are produced cyclotrons (particle accelerators). Commercial radioisotopes have an economic use, and are produced by: Nuclear Reactor (Lucas heights): the nuclear fission of uranium releases a steady stream of neutrons. These neutrons are used to produce neutron-rich isotopes. In a Particle accelerator (at UOS) small nuclei are fired at high speed into larger nuclei to produce proton-rich (neutron-poor) isotopes. Eg. 18 F is incorporated into fluorodeoxyglucose (FDG) where an F replaces an OH. FDG is injected into a patient s bloodstream and readily absorbed by cancer cells. The 18 F undergoes positron emission to form 18 O. The emitted positron collides with an electron and both are annihilated, producing two -rays, which are detected by a PET scanner.

27 /7 Identify one use of named radioisotope used in medicine and industry, and its use in terms of it s chemical properties. Industry: Cobalt-60 is a -emitter with long half-life (5.3 years), inert, and easily stored. It is used for: - Gamma sterilisation of: -medical supplies (Eg. bandages are ruined by heat sterilisation) -food (to destroy microorganisms to extend shelf-life eg. poultry, fruit.) - Radiation source to destroy cancer cells (which are more susceptible to radiation) - Radioactive source in automated thickness gauges. -Inspect metal parts and welds for defects (in aircraft), as Co-60 produces a beam of -rays which can penetrate metal parts, and the amount of radiation that passes through shows if there are cracks or not. o Made at Lucas heights: Chemistry Notes: [ ] square brackets mean concentration. Always draw every bond in structural formula. (even bond between O and H in ethanol) Only put calculations to the least number of significant figures given in the question. Bond forming releases energy. Ethanol in fermentation experiment is aqueous but in combustion is liquid Remember states! Write 130g etc. as 130.0g Compare questions use table At SLC Methane, ethane, propane and butane are gases. At SLC Pentane through hexadecane(16) are liquids, all larger are solids. At SLC methanol, ethanol, propanol, butanol etc are liquids.

28 Medicine: Technetium-99m (m metastable state) is used in over half of nuclear medicine procedures especially as a radio-tracer due to: o The isotope has a short half-life of 6 hours (can investigate changes with minimum extended exposure). Is also quickly eliminated from body. o Is reactive and several different oxidation states, enabling production of different biological chemicals to target different organs or tissues. o Gamma rays emitted cause minimal damage to body, but can easily be detected by gamma ray sensitive camera. The Tc-99m is chemically attached to a biological molecule (which acts the same as a normal molecule) will concentrate in the targeted organ. And by looking at how the chemicals accumulate in certain areas, help determine functioning of that body part. Eg. Tc-99 can be combined with tin to be injected into the bloodstream, to trace blood flow and assess the heart. Made in portable generator : Analyse benefits and problems associated with radioactive isotopes in industries and medicine. Note: use is described above. Cobalt-60 Benefits: Cheaper and more reliable than heat or chemicals for sterilisation, and energy level is ideal for metal imaging without having to open the metal Tc-99m Benefits: Appropriate half-life, and variety of chemical compounds which can target organs without needing surgery. Radioisotope Problems: The safety of the people who work with radioactive materials is the biggest problem. The Ionising ability of radiation causes electrons to be removed from atoms and molecules such as DNA, and therefore increases the risk of genetic mutations and development of cancers. The key to safety is effective packaging and shielding of the material, and constant monitoring for escaped radiation.