C6 Revision

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  • Created on: 14-06-16 20:34
What is chemical synthesis?
The process of making complex chemicals from simpler ones.
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Give four examples of useful products made by the chemical industry.
1)Food additives.2)Cleaning and decorating products.3)Drugs.4)Fertilisers.
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Describe food additives.
Produces preservatives,colourings and flavourings for food producers.
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Describe cleaning and decorating products.
Paints contain lots of pigments and dyes,which have been developed by chemists. Products like bleach,oven cleaner and washing up liquid also made by chemists.
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Describe drugs.
Pharmaceutical industry huge.Drugs you take gone through lots of development before you use them.
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Describe fertilisers.
Use million tonnes of fertilisers per year.Contain lot of ammonia-produced by chemical industry.
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As well as figuring out how to make chemicals, what else to chemists do?How do they do this?
Find out how to get the highest yield by controlling rate of reaction.
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What do chemists have to think about when finding new ways to make chemicals?
Environmental impact.
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What kind of scale can chemicals be produced?
Large scale or small scale.
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How are some chemicals produced?Give an example.
Massive scale, e.g. 150 million tonnes of sulfuric acid produced globally per year.
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What are uses of sulfuric acid?
Car batteries and fertilise production.
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What does the chemical industry make up a significant chunk of?
The economy.
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How many people are employed in the chemical industry in the UK?
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What happens to chemicals when they have been made?
Some sold directly to consumers and others sold to other industries as raw materials for other products.
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Which industry has the largest share in the chemical industry?
The pharmaceutical industry.(37%).
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What does the PH scale range from?
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Describe acidic compounds?Give examples.
Can be solid e.g. citric acid(used as food additive).Liquids e.g. ethanoic acid(in vinegar)or gases e.g. hydrogen chloride.
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Describe alkalis.
Include sodium hydroxide(makes cleaning products like bleach.Potassium hydroxide(alkaline batteries)and calcium hydroxide (used to neutralise acidic soils).
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What do indicators contain?
A dye that changes colour depending whether it's above or below a certain PH.
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What are 3 types of indicator?
1)Litmus paper.2)Universal indicator.3)pH metres.
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Describe litmus paper.
Easy way to see if solution is an acid or alkaline red=acid blue=alkaline.
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Describe universal indicator.
Useful combination of dyes, useful for estimating pH. Red=acid.Blue=alkaline.
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Describe pH meters.
Measure pH of substance. Probe dipped into substance,meter gives reading.
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Which of these indicators are the most accurate?
pH metres.
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What pH do acids have?
pH less than 7.
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What ions do acidic compounds produce?
Aqueous hydrogen ions H+(aq) in water.
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What pH do alkalis have?
pH higher than 7.
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What ions do alkaline compounds produce?
Aqueous hydroxide ions OH-(aq), in water.
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What is produced when acid and alkalines react together?
Salt and water(neutral).
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What happens to the ions in a neutralisation reaction?
Hydrogen ions (acid) react with hydroxide ions (alkali) to make water(neutral).
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What does a reaction between an acid and a metal produce?
Salt and hydrogen.
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Explain an example experiment using acids and metals.
1)More reactive the metal,faster the reaction.2)If metal is less reactive than hydrogen-no reaction.3)Speed of reaction indicated by rate hydrogen bubbles given off.4)Use squeaky pop to test hydrogen.5)Name of salt depends on metal and acid used.
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What will a reaction with hydrochloric acid always produce>
Chloride salts.
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What will a reaction with sulfuric acid always produce?
Sulfate salts.
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What does a reaction between an acid and metal oxide produce?
Salt and Water.
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What does a reaction between an acid and a metal hydroxide?
Salt and water.
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What does a reaction between an acid and metal carbonate produce?
Salt and water and carbon dioxide.
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What are the 7 stages involved in chemical synthesis?
1)Choosing the reaction.2)Risk assessment.3)Calculating quantities of reactants.4)Choosing apparatus and conditions.5)Isolating the product.6)Purification.7)Measuring yield and purity.
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Describe the reactions chemists could choose.
1)Neutralisation-acid and alkali react to produce salt.2)Thermal decomposition-heat used to break compound into simpler substances.3)Precipitation-insoluble solid formed when 2 solutions mixed.
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Describe the risk assessment.
Identify hazards, assess who might be harmed,decide actions that can be taken to reduce risks.
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Describe calculating the quantities of reactants.
Use balanced symbol equation to calculate amount of reactant needed to produce product.Means there is no waste.
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Describe choosing apparatus and conditions.
Apparatus needs to be correct size and strength.Need to decide temperature, concentrations and whether a catalyst should be used.
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Describe isolating the product.
Products may need to be separated, could involve evaporation,filtration and drying.
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Describe purification.
As you isolate product, it is purified. Crystallisation useful to purify.
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Describe measuring yield and purity.
Yield tells you about overall success of process-compare expected amount with actual amount.Purity needs to be measured
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What are 3 techniques used for isolating and purification?
1)Filtration.2)Evaporation and crystallisation.3)Drying.
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Describe filtration.
1)Isolating-Separates insoluble solid from a liquid e.g. pharmaceutical industry to separate aspirin.2)Purification-e.g. solid impurities in reaction can be separated using filtration.
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Describe evaporation and crystallisation.
1)Isolating-evaporating solution leaves behind solid crystals.2)Purification-Crystals have structure that impurities can't fit into.3)Processes often repeated to improve purity.Products dissolved then crystallised again(recrystallisation).
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Describe drying.
1)Product dried in drying oven-some heat sample,others blow hot air over product(like hairdryer).2)Dried using desiccators-contain chemicals like silica gel that remove water-help keep product dry.
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What is actual yield?
Mass of pure,dry product.Depends on amount of reactants used.
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How is actual yield measured?
By weighing dried product.
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What is theoretical yield?
Maximum possible mass that could've been made using reactants you started with.
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How is theoretical yield measured?
Calculated from balanced equation.
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What is percentage yield?
Actual yield as a percentage of the theoretical yield.
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How is percentage yield calculated?
(Actual yield(in grams)/Theoretical yield(in grams))x 100.
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What can titrations be used for?
Check purity of an acid or alkaline product.
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How do titrations work?
By using a neutralisation reaction.
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Describe a titration.
1)Add known volume of alkali to titration flask-with 2/3 drops of indicator.2)Fill burette with acid.3)Use burette to add acid to alkali bit at a time-make sure to swirl flask.4)Go slow when neutralisation is about to occur.Continued...
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Titrations continued.
5)Indicator changes colour when neutralisation occurs.6)Record volume of acid needed to neutralise alkali.
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What does a burette do?
Lets you measure different volumes and add the solution drop by drop.
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True or False-titrations can be carried out on solid and liquids?
False- can only be done on liquids.
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Explain how a solid can be turned into a liquid so a titration can be done.
1)If it's a solid lump,crush into powder.2)Put titration flask on balance.3)Weigh some of powder into flask.4)Add solvent e.g. ethanol or water,to dissolve powder.5)Swirl titration flask until all powder is dissolved.
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When does the purity of a product improve?
When it's being isolated.
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What processes need to be repeated to get a really pure product?
Filtration, evaporation and crystallisation.
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Explain using 2 examples why the purity of a product is important.
1)In pharmaceutical industry-if there are impurities may cause harm.2)Petrochemicals-if there are impurities in petrol products could damage car's engine.
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What else can titrations be used for?
To measure the purity of a substance.
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How many cm are in a dm?
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What is the formua for mass/
Mass=Concentration x Volume.
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What is the formula for purity?
(Calculated mass of substance/mass of substance at start)x 100.
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What are the two types of reaction(in terms of energy)?
Endothermic ans exothermic.
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What is exothermic?
Gives out energy to surroundings usually in form of heat-shown by temperature rise.
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What is endothermic?
Takes in energy from surroundings usually in form of heat-shows fall in temperature.
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What do energy level diagrams show?
Levels of reactants and products in a reaction.
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What is an exothermic graph like?
Starts of higher, rises of then drops.
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What is an endothermic graph like?
Starts of low, rises then dips.
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What are the labels on these graphs?
Y axis=energy. X axis=Progress of reaction.
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Why is energy management important to control reactions?
1)If reaction is exothermic heat has to be removed or temperature will increase.2)If temperature increases,so will rate of reaction-mixture hotter.3)If mixture hotter,reactants may turn to gas-increase pressure and cause explosion.Continued..
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Energy management continued...
4)If reaction is endothermic, heat needs to be provided or reaction will get too cold.5)Could slow rate of reaction or cause mixture to freeze-damage equipment and stop process.
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What does the rate of a reaction mean/
How fast the reactants are changed into products.
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What are examples of slow reactions?
Rusting of iron.Chemical weathering.
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What is an example of a moderate reaction?
Metal reacting with acid to produce bubbles.
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What is an example of fast reactions?
Burning and explosions.
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What are 2 reasons why controlling the rate of reaction is important?
1)Safety.2)Economic reasons.
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Describe how reactions can be made safe.
If reaction is too fast, may cause explosion-dangerous.
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Describe economic reasons why the rate of reaction is important.
Costs a lot e.g. high temperature means higher fuel bills, faster rate means more product made.
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What do companies need to do in terms of the rate of reaction and production costs?
Use low production costs so the rate of reaction or yield is lower.
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What 4 things can cause an increased rate of reaction?
1)Temperature increase.2)Concentration increase.3)Catalyst added.4)Solid crushed to smaller bits.
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What do all of these things cause?
More collisions between reacting particles.
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Explain how increasing the temperature increases the rate of the reaction.
1)Causes particles to move faster.2)If they move faster, will collide more frequently.3)Faster they move, more energy-enough energy to make reaction happen.
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Explain how increasing the concentration increases the rate of the reaction.
1)Higher concentration=more particles of reactant in same volume of solvent.2)Makes collisions more likely.
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Explain how smaller solid particles increases rate of reaction.
1)Increases surface area.2)Particles have more area,collisions more frequent.3)E.g. soluble painkillers dissolve faster when broken into bits.
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Explain how a catalyst increases the rate of the reaction.
1)Catalyst increases speed of reaction without being changed or used up.2)Works by giving reacting particles surface to stick to-more successful collisions.
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How can the rate of the reaction be calculated?
Amount of reactant used or formed/time.
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What are 3 ways how the speed of the reaction can be measured?
1)Precipitation and colour change.2)Change in mass.3)Volume of gas given off.
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Explain how precipitation and colour change can be used to measure the speed of a reaction.
1)Precipitate-observe mark and measure time it takes to disappear.2)This only works for reaction where solution is see-through.3)Colour change-measure time it takes for colour to change.4)Results may not be accurate as people may not agree change.
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Explain how change in mass can be used to measure the speed of a reaction.
1)Produces gas-measured using mass balance.2)As gas is released,mass disappears-can be easily measured.3)Quicker reading dropped,faster reaction.4)Most accurate method but releases gas into room.
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Explain how the volume of gas can be used to measure the speed of a reaction.
1)Use gas syringe to measure volume of gas.2)More gas given during certain time,faster the reaction.3)Quite accurate but can be vigorous.
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