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| Frage | Antworten |
| What is crude oil made up of ? | It is a mixture of compounds called hydrocarbons |
| What is the general formula for alkanes ? |
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| Describe the structure of an alkane | It is a hydrocarbon that only contains single bonds between the carbon atoms, so they are known as saturated compounds. The carbons and hydrogens are bonded together with a covalent bond |
| What are the first 5 alkanes, and what are their chemical formula? | 1. Methane C H4 2. Ethane C2 H6 3.Propane C3 H8 4.Butane C4 H10 5.Pentane C5 H12 |
| What happens to the properties of alkanes as they increase in chain length? | They flow less (become more viscous) They become less flammable They become less volatile (doesn't evaporate as easily) Their boiling point increases |
| What is the word equation for a combustion reaction with an alkane ? | Alkane + Oxygen -> Carbon dioxide + Water |
| What is the balanced symbol equation when methane reacts with oxygen in a combustion reaction ? | CH4 (g) + 2O2 (g) ----> 2H2O (l) + CO2 (g) |
| Why does the boiling point of an alkane increase as the molecules get longer? | The intermolecular forces in the alkane becomes stronger as chain length increases, so more energy is required break these bonds |
| Why are alkanes very unreactive? | The C-C and C-H bonds are difficult to break They don't react with any aqueous reagents (substances dissolved in water) |
| Describe the structure of alkenes | They are hydrocarbons with a double covalent bond between two carbon atoms, so are known as unsaturated (the carbon atoms are bonded to fewer hydrogen atoms than they could be). |
| What is the general formula for alkenes? |
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| What is the structure formula of ethene, propene and butene? |
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| What is the rule for the alkenes name, and what are the first 4 alkenes called ? | Rule: ends in -ene 1. Ethene C2 H4 2. Propene C3 H6 3. Butene C4 H8 4. Pentene C5 H10 |
| Do alkenes combust (react with oxygen) ? | Yes, and produce water and oxygen Alkene + Oxygen -> Carbon dioxide +Water |
| What can the incomplete combustion of a hydrocarbon produce? | Carbon and carbon monoxide ( a poisonous gas) |
| What colour does a flame turn if carbon is present? | Yellow |
| How can we test for an alkene, and what is the structural formula when this reaction occurs with ethene? |
We can test for alkenes using bromine water, because the double bonds react with the bromine- the red/ orange bromine water goes colourless. This is called an addition reaction.
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| What is a functional group? | They are the groups of atoms in a molecule responsible for that molecules reactivity e.g. for alcohols it is -OH |
| What is a homologous series? | Different molecules with the same functional group- a series of compounds with the same general formula |
| What is an organic compound? | One which contains carbon |
| What is the functional group, and general formula for alcohols? |
Functional group: -OH
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| What are the first 4 alcohols and their symbol equations ? | 1. Methanol C H3 OH 2. Ethanol C2 H5 OH 3. Propanol C3 H7 OH 4. Butanol C4 H9 OH |
| Draw the structual formula of methanol and ethanol |
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| What are the main properties of alcohols? | 1. They are liquids at room temperature: The -OH group increases the size of the intermolecular forces between the molecules, so the boiling point is higher 2. They mix with water: The -OH group helps it dissolve in H-O-H 3. Flammable: The hydrocarbon part C-H can burn, and is flammable 4. Reacts with sodium: The -OH group means that they react in a similar manner as water with sodium |
| Are alcohols and alkanes soluble and volatile? | Ethanol is soluble in water Alkanes are insoluble in water Ethanol, methane and ethane are all volatile |
| Name one similarity between water and alcohols other than their reactivity | They are both good solvents Alcohols can dissolve lots of compounds e.g. hydrocarbons and oils, which water can't, so they are very useful in industry |
| What is the difference between the reactions of sodium with ethanol, and sodium with water? | Sodium + Ethanol ---> Sodium ethoxide + Hydrogen The reaction isn't as strong Sodium + Water ---> Sodium hydroxide + Hydrogen The sodium fizzes. and reacts very violently (sometimes the Na melts due to the heat) Water and ethanol both react, because they contain the -OH group |
| Name some uses of alcohols in manufacturing | Methanol is used as a starting point for manufacturing other organic chemicals Ethanol is used in perfumes and aftershave lotions as it can mix with oils ( smell) and water (bulk) Methylated spirits is ethanol with other chemicals added to it (e.g. methanol), and is used to clean paint brushes and as fuel etc. Pure ethanol and other alcohols is sometimes mixed with petrol, and is used as fuel for cars |
| How can alcohols e.g. ethanol be produced? | In an addition reaction: Ethene + Steam ----> Ethanol During fermentation: Glucose -----> Ethanol + Carbon dioxide |
| How can ethanol be produced through fermentation? | Fermentation uses yeast to convert sugar into ethanol and carbon dioxide The yeast cells contain zymase, which is an enzyme that acts as a catalyst in fermentation This enzyme works fastest at 30 degrees C, and at a pH of 4 |
| Why is it important to prevent oxygen getting in the fermentation process? | Oxygen converts the ethanol to ethanoic acid, which reduces the pH; this can stop the enzyme from working, as it denatures |
| Why does the fermentation process stop when the concentration of ethanol reaches 10 to 20% ? | The ethanol kills off the yeast cells (it is toxic to them), so they can't produce any more products |
| How can ethanol sollution be concentrated? | With distillation |
| What are the main stages of distillation to produce concentrated ethanol? | 1) The ethanol solution is put in a flask below a fractionating column 2) The solution is heated, so the ethanol boils, and the ethanol vapour travels up the column, cooling as it gets higher 3) The temperature is chosen so that anything that has a higher boiling point (water) cools to a liquid and flows back down the column 4) Only the pure ethanol vapour reaches the top of the column, and this flows through a condenser, where it is cooled to a liquid |
| What information may you need to find out to see whether a process in sustainable? | Will the raw materials run out? How good is the atom economy? What will you do with the waste products? What are the energy costs? Will it damage the environment? What are the health and safety risks? What are the benefits and risks to society? Is it profitable? |
| How can ethanol be made from waste biomass? | Waste biomass is the parts of a plant that would normally be thrown away e.g. corn stalks, rice husks and wood pulp This can't be fermented in the normal way, because it contains a lot of cellulose, which can't be converted by yeast into ethanol E. coli bacteria can be genetically modified, so they can convert the cellulose into ethanol |
| Main the two main stages that convert ethane into ethanol | Ethane is found in crude oil and natural gas, and it is cracked to form ethene and hydrogen gas Ethene then reacts with steam to make ethanol; conditions needed: 300 degrees C, 70 atmospheres and phosphoric acid as a catalyst ethane ----> ethene + hydrogen ethene + steam ----> ethanol |
| Why is ethane used to make ethanol on an industrial scale? | This method allows high quality ethanol to be produced continuously and quickly Fermentation is too slow to make ethanol on a large scale |
| What is the functional group of carboxylic acids? | -COOH |
| What is the general formula for carboxylic acids? |
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| What are the first 3 carboxylic acids and their structural formula ? |
Methanoic acid
Ethanoic acid
Propanoic acid
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| How are carboxylic acids usually formed? | By the oxidation of alcohols ethanol + oxygen ---> ethanoic acid + water |
| What kind of acids are carboxylic acids? | They are weak acids, so are less reactive than strong acids e.g. sulfuric acid- they have a lower pH |
| Why are carboxylic acids weak? |
When dissolved in water, the H+ ions make it acidic, but only very few of these ions are formed, so it is weak
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| How do carboxylic acids react? | Just like other acids They react with alkalis, carbonates and reactive metals |
| What is the name of a salt, which is formed in a reaction that involves carboxylic acids ? | It ends in -anoate e.g. ethanoic acid forms an ethanoate |
| What is the word and symbol equation when a metal reacts with a carboxylic acid ? | carboxylic acid + metal ----> salt + hydrogen e.g. ethanoic acid +magnesium ----> magnesium ethanoate + hydrogen 2CH3COOH + Mg ---> Mg(CH3CO2)2 + H2 |
| What is the word and symbol equation when a metal carbonate reacts with a carboxylic acid ? | carboxylic acid + metal ----> salt + water + carbon dioxide e.g. ethanoic acid + magnesium carbonate ---> magnesium ethanoate + water + carbon dioxide 2CH3COOH +MgCO3 ---> Mg(CH3CO2)2 + H2O + CO2 |
| What is the word and symbol equation when an alkali reacts with a carboxylic acid? | carboxylic acid + alkali ----> salt + water e.g. ethanoic acid + magnesium hydroxide ---> magnesium thanoate + water 2CH3COOH +Mg(OH)2 ---> Mg(CH3CO2)2 + 2H2O |
| What are the main properties of carboxylic acids ? | Pungent/ unpleasant smell pH of around 4- red in universal indicator They react like any other acid |
| What is the bond holding together sodium ethanoate? |
An ionic bond
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| How is an ester formed? |
An alcohol and a carboxylic acid can react together to form an ester- in an esterification reaction:
(This reaction requires warming and a strong acid as a catalyst e.g. sulphuric acid)
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| How is an ester named? | 1st part: from the alcohol e.g. ethyl, propyl, butyl 2nd part: from the carboxylic acid e.g. ethanoate, propanoate, butanoate |
| What is the functional group of esters? | -COO- |
| What are the main properties of esters? | They are volatile, so the molecules easily evaporate They have pleasant smells- often sweet They can act as solvents |
| What are esters used for? | Flavourings Perfumes Solvents for paints, ink, glue etc. As plastercisers- make plastics more flexible |
| What is hydrolysis? | When an ester reacts with water and forms an acid and an alcohol |
| How can a soap be formed? | When a strong alkali e.g. calcium hydroxide is used as a catalyst during the hydrolysis of an ester |
| What are fatty acids? What is glycerol? What is formed when they react together? | Fatty acids are carboxylic acids with long carbon chains Glycerol is an alcohol When they react together fats and oils are made |
| What are the two main types of fatty acids? | Saturated (only C-C bonds) and Unsaturated (some C=C bonds) |
| How is fat useful for organisms? | They have a lot of energy packed into them, so they are good at storing energy When an organism has excess energy, some of it is stored as fat- this can then be used later on when it is needed |
| What are the two main properties of animal fats? | e.g. butter They are solids at room temperature They are mainly saturated hydrocarbon chains |
| What are the two main properties of vegetable oils? | e.g. sunflower oil They are liquids at room temperature- molecules aren't straight, so it is more difficult for them to pack together They are mainly unsaturated hydrocarbon chains |
| What are soaps? | The sodium or potassium salts of fatty acids |
| What is the structure of glycerol? |
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| What are the 4 main stages of making an ester? | Refluxing Distillation Purification Drying |
| What is refluxing? | The mixture of the alcohol and carboxylic acid is gently heated in a flask which also contains a strong acid e.g. sulfuric acid as a catalyst The flask is fitted with a condenser, which catches the vapour (evaporated reactants), and then allows them to condense. This means that they drop back down into the flask without being lost, so all the reactants can react to form an ester. |
| Why is distillation important when making an ester? | This separates the ester from the other chemicals still in the flask The mixture is heated below a fractionating column, and as the solution starts to boil, the vapour goes up this column. The temperature at the top of the column is the boiling point of the ester, so this liquid flows out of the condenser and is collected- an impure ester |
| Why is purification important when making an ester? | It purifies the ester The mixture is poured into a tap funnel, and mixed with sodium carbonate solution to remove any acidic impurities It is then mixed with calcium chloride (once all the water has been removed through tapping) to remove any ethanol |
| Why is drying important when making an ester? | Any remaining water can be removed by shaking it with lumps of anhydrous calcium chloride, which absorbs the water The pure ester can be seperated from the solid CaCl2 by filtration |
| What is the atom economy? | A measure of the efficiency with which a reaction uses its reactant atoms |
| How can the atom economy be calculated? | mass of atoms in the desired product ------------------------------------------------------- mass of the atoms in the reactant x 100 |
| What are bulk chemicals? | Chemicals that are made in very large quantities e.g. fertilizers, sulfuric acid, ammonia and sodium hydroxide |
| What are fine chemicals? | Chemicals that are made in small quantities with high purities e.g. medicines, perfumes and food additives |
| What can be done to a process to make it more 'Green' ? | Waste prevention High atom economy Less hazardous chemical synthesis Designing safer chemicals Catalysis Pollution prevention Use of safer solvents and auxiliaries Use of renewable feedstocks Design for energy efficiency Design for degredation Reducing derivatives Safer chemistry for accident prevention |
| How can percentage yield be calculated? | Actual yield ------------------------ Theoretical yield x100% |
| Name some exothermic reactions | neutralisation reaction water turning into ice combustion reaction |
| Name some endothermic reactions | thermal decomposition water turning into steam- evaporation requires energy to occur |
| Why do boiling points differ between substances? | Some bonds are stronger than others, so will require varying amounts of energy to break them |
| What kind of reactions are making and breaking bonds? | Making bonds releases energy- exothermic Breaking bonds requires energy- endothermic MEXOBENDO |
| What is the equation to find the enthalpy change/ energy change of a reaction? | Bonds in reactants - Bonds in products If the answer is negative the reaction is exothermic If the answer is positive the reaction is endothermic |
| What does a catalyst do? | It lowers the activation energy required to start the reaction by giving an alternative route. This speeds up the rate of reaction |
| What is a reversible reaction? | The symbol ⇌ is used to show that the reaction can occur in both direction, as the products can react together back into the reactants |
| What is dynamic equilibrium? | When the rate of the forwards reaction is equal to the rate of the backwards reaction The number/ concentration of reactants and products present should always stay the same, but the reaction is still occuring |
| What are Le Chatelier's principles? | It states that whatever change we make to the conditions of a reaction at equilibrium, the reaction acts to reverse this change |
| What conditions can we change in a reaction? | Concentration Temperature Pressure |
| If A + B ⇌ C (exothermic) What is the backwards reaction? | Endothermic due to the conservation of energy |
| A + B ⇌ C What will the reaction do if the concentration of A is increased? | The reaction will want to reduce the concentration of A, by favouring the other side of the reaction It will try to produce more of C, so increases the concentration of substances of the products too |
| A + B ⇌ C (exothermic) What will the reaction do if the temperature increases? | The reaction will want to reduce the temperature, by favouring the endothermic reaction It will try to produce more A and B, as this is the endothermic reaction, so takes in some of the heat |
| A + B ⇌ C What will the reaction do if the pressure increases? | The reaction will want to reduce the pressure by favouring the reaction that produces less molecules of gas It will try to produce more C, as in the forward reaction only one molecule is produced, whereas the backwards reaction produces two molecules |
| What is the word and symbol equation for the Haber process? |
Nitrogen + Hydrogen ---> Ammonia
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| What are the feedstocks for the Haber process? | nitrogen and hydrogen |
| Ideally what conditions would their be to increase the amount of ammonia produced? | Decrease the temperature Increase the pressure Increase the concentration of nitrogen and hydrogen |
| What are the conditions used for the Haber process when done industrially? | Temperature : 450 °C Pressure: 200 atmospheres Catalyst: Iron |
| Why is 450°C used industrially for the Haber process even though this favours the endothermic reaction, which produces N2 and H2 ? | If the temperature is any lower, the rate of reaction would be so slow that it wouldn't be profitable- the catalyst is also added to increase the rate of reaction The temperature is put in the middle, as making it hotter would further increase the rate of reaction, but this may result in a lower yield of ammonia |
| Why is a pressure of 200 atmospheres used in the Haber process? | A higher pressure may be dangerous and too costly, but it is still very high, so a lot of ammonia should be produced |
| What happens to the hydrogen and nitrogen molecules that don't react in the reaction vessel? | It doesn't stay in the reaction vessel for long, but it is recycled and passes through the vessel again. This means that none is wasted and more ammonia will be formed |
| What is the main use of the Haber process? | It produces ammonia, which is used in fertilisers Nitric acid and ammonia react together to form ammonium nitrate- a commonly used fertiliser |
| Why are fertilisers important? | They play a vital part in world food production, as they increase crop yields, so help to feed more people |
| What are the other uses of ammonia? | It is important in industry where it is used to manufacture plastics, explosives and pharmaceuticals |
| What are some negatives of the Haber process? | Fertilisers can cause eutrophication and water pollution |
| Where do the nitrogen and hydrogen that are neede in the Haber process come from? | The nitrogen comes from the air (78%) The hydrogen comes from the cracking of chemicals in natural gas |
| What is nitrogen fixation? | The process of turning N2 from the air into useful nitrogen compounds e.g. ammonia |
| How can nitrogen fixing bacteria 'fix' nitrogen at room temperature and pressure? | Using enzymes- biological catalysts |
| What is needed before new chemical products are made? | Lots of research and development |
| To make a new production process run efficiently a new catalyst might have to be found- what are the main steps of this? | 1) Testing potential catalysts using a process of trial and error 2)Making computer models of the reaction to try and work out which substance might work as a catalyst 3) Designing or refining the manufacture of the catalyst - make sure the product can be mass produced safely, efficiently and cost effectively 4) Investigating the catalyst's risks to the environment, and how these can be reduced 5) Monitoring the quality of the product to make sure it isn't affected by the catalyst |
| What do government regulations do? | They protect workers, the general public and the environment |
| What kind of government regulations exist for chemical processes? | 1) Using chemicals- sulfuric acid is sprayed on potato fields to make harvesting easier; government regulations restrict how much acid can be used, and signs have to be put out to warn the public 2)Storage- dangerous chemicals have to be stored in locked storerooms, and poisonous chemicals must be stored in either sealed containers or well- ventilated store cupboards 3) Transport- lorries transporting chemicals must display hazard symbols and identification numbers to help emergency services deal safely with any accidents or spills |
| What are the 5 main stages involved in producing a chemical? | 1. Raw materials are converted into feedstock 2. Synthesis 3. The products are separated 4. The purity of the product is monitored 5. By- products and waste are dealt with |
| What is the difference between raw materials and feedstock ? | Raw materials are the naturally occurring substances which are needed e.g. crude oil and natural gas Feedstocks are the actual reactants needed for the process e.g. hydrogen and ethanol The raw material usually have to be purified or changed in some way to make the feedstock |
| What is chemical synthesis? | The feedstock (reactants) are converted into new chemicals (products) The conditions are carefully monitored and controlled to make sure the reaction occurs at a reasonable rate |
| Why do the products have to be seperated? | Chemical reactions usually provide the required substance and other chemicals known as by- products. There may also be some left over reactants, so everything is separated, so it can be dealt with in different ways |
| Why is the purity of the product monitored? | Even after all the chemicals have been separated, they may still not be perfectly pure The purity has to be monitored to make sure it is between certain levels and safe to use- medicines have to be very pure |
| How are by- products and waste dealt with? | Where possible by- products are sold or used in another reaction If the reaction is exothermic, it will release heat- this excess heat can be used to produce steam or hot water for other reactions, saving energy and money There are legal requirements about carefully disposing of waste products, so it doesn't harm people or the environment |
| What is qualitative and quantitative analysis ? | Qualitative analysis tells you which substances are present in a sample Quantitative analysis tells you how much of a substance is present in the sample |
| Why is chemical analysis carried out on samples? | It might be difficult and expensive to test all of the material, and it means that the rest can be used for its actual purpose If something goes wrong with the analysis, another sample can be used The sample has to represent all the chemical, so a mean can be calculated |
| How is a solution made? | By dissolving the sample in a solvent |
| What are the two main types of solution? | Aqueous solutions: the solvent is water- they're shown by the state symbol (aq) Non- aqueous solutions: the solvent is anything other than water e.g. ethanol |
| What are standard procedures? | They are agreed methods of working that are safe, effective and accurate They can be agreed within a company, nationally or internationally They are there for the collection, storage and analysis of a sample, so results should always be very similar |
| What is chromatography used for? | To identify and separate chemicals in a mixture To check the purity of a sample To purify small samples of a chemical |
| What are the two phases used in chromatography? | The mobile phase: The solvent or gas that moves up/ along the stationary phase- the molecules can move The stationary phase: The material that doesn't move, and it is always a solid or really thick liquid |
| How can the Rf value be calculated? | Distance traveled by the sample --------------------------------------------------- Distance traveled by the solvent |
| Why do different chemicals seperate out and end at different points? | How quickly a chemical moves depends on how it distributes itself between the two phases |
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