Chemistry C3

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What does the rate of reaction measure?
How much product is formed in a fixed period of time.
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What usually happens to the rate of a reaction as it progresses, and why?
They are usually fast at the start and then slow down as the reactants are used up
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How can the rate of reaction be worked out?
From the gradient of the graph
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What is the formula for gradient?
Gradient= Y/X
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What is the limiting reactant?
The reactant that is not in excess, that gets used up in the reaction.
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What is the limiting reactant directly proportional to?
The amount of product formed in the reaction
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When do reactions occur?
When particles collide together
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How can the mass of gas collected at 15 seconds be estimated?
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How can you use extrapolation to work out the gas collected?
By using the initial line of the graph. Extrapolation means making an estimate outside of results collected.
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What does the rate of reaction depend on?
The number of collisions between the reacting particles.
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Finish this sentence: Therefore, the higher the number of collisions...
The faster the rate of reaction.
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In what three ways can the rate of reaction be increased?
Increasing the concentration, or raising the temperature or pressure.
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How does increasing the concentration increase rate of reaction?
The particles become more crowded, which increases the number of collisions per second.
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How does increasing the temperature increase rate of reaction?
As the temperature increases, the particles gain kinetic energy, so they move faster and increase the number of succesful collisions per second.
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How does increasing pressure increase the rate of reaction?
The pressure forces the particles together, increasing the rate of reaction.
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What is required to create a succesful collision?
The particles must have enough energy to react.
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What can combustible powders cause?
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What do some powders react with, and what do they produce?
Some powders react with oxygen, to produce carbon dioxide and water vapour
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Name three examples of combustible powders.
Flour, custard powder, sulfur
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How can owners of factories that produce these powders make sure explosions dont occur?
By making sure the powders cant reach the open atmosphere, and making sure the chances of a spark being produced nearby is very small
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What does breaking blocks into smaller pieces do in terms of surface area?
It increases the surface area
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Which has a larger SA, a powder or a solid block of substance?
The powder has a large SA
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Finish this sentence: As the SA of a solid is increased...
So is the rate of reaction
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Why do powders increase the rate of reaction?
Because more surface is available to react with than in solid block form.
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What is the role of a catalyst?
To increase the rate of reaction whilst remaining unchanged at the end of a reaction.
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Which number is the ATOMIC NUMBER in the periodic table?
The largest number shown for each element.
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What is conservation of mass?
When, in any chemical equation, the total mass of the reactants equals the total mass of the products.
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Why is mass ALWAYS conserved?
Because atoms cannot be created or destroyed, only rearranged
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How would you work out this type of question: Find the mass of _________ needed to make 20g of ___________.
You would write the balanced symbol equation, work out the relative atomic mass, add g for grams to the end of the relative atomic masses, and then scale them up or down to fit 20g.
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Why is the actual yield produced always less than the predicted?
Because of losses in the practical methods used
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What is the formula for percentage yield?
percentage yield= actual yield/predicted yield x100
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Why do industrial processes need to have as high a percentage yield as possible?
To reduce the amounts of reactants wasted, because it is wasteful and costly, and to reduce their costs by ensuring that enough reactants are used, as too little reduces the amount of product.
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What is the formula for ATOM ECONOMY?
Atom economy= Relative atomic mass of desired products/Relative atomic mass of all product x100
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Why does industry want as high and atom economy as possible?
To reduce production of unwanted products that need to be disposed of, which costs money, and to make the process more sustainable by making better uses of the reactants
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Bond breaking is...
an endothermic process
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Bond making is...
an exothermic process
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How can you determine if a reaction was overall exothermic or endothermic?
By comparing the amount of energy released and the amount needed
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When is a reaction endothermic?
If more energy is needed than is released.
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When is a reaction exothermic?
If more energy is released than needed.
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What is the formula for energy transferred by a fuel?
Energy transferred(J)= mass in water heated(g) X specific heat capacity of water X temperature change
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What is the specific heat capacity of water?
4.2J/g celsius
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How can the mass of fuel burnt be found in an experiment?
By weighing it before, and after burning it.
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What formula is used to find the energy per gram?
Energy per gram= enery released(J)/ mass of fuel burnt (g)
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What process is used to make chemicals needed in large amounts?
Continous process
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Name 2 chemicals that are made using the continous process?
Ammonia and sulfuric acid
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Describe the continous process
Makes large amounts of products, 24 hours a day, 7 days a week, takes place in large chemical plants, are mostly automated so the labour costs are minimised, takes less energy to maintain as is is constantly running
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What process is used to make chemicals needed in small quantities?
Batch process
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Name one type of chemcial made using the batch process
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Describe the batch process
It makes a fixed amount, the batches can be stored until needed, allows chemicals being made to be sold as they usually have a sell by date, it is easy to make a new batch, and it is easy to change the product being produced.
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What are the disadvantages of the continous process?
The process is inefficient if not constantly running, and there is a high initial cost to set it up.
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What are the disadvantages of the batch process?
Each batch has to be supervised so costs a lot for labour, time is needed to clean if the product is changed, and it is inefficient as it is not in use all the time.
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How are drug prices set?
They are set to take account of development costs.
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How long can it take for a new drug to be properly tested?
About 10 years
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Where are most of the raw materials found, and how does this increase costs?
They are found in plants, and are very difficult to extract.
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Describe the process of extracting a chemcial from a plant
The plant is crushed to disrupt and break cell walls, it is boiled in a substance that dissolves the compound, chromatography seperates and identifies the useful compounds, and the compounds are isolated, purified and tested.
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How is thin layer chromatography used to test the purity of a compound?
By comparing the speed of movement against a known pure sample.
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Why is it so difficult and costly to gain a liscense for a new drug? continued on next slide
Thousands of compunds usually have to be tested to find the most effective one, they have to be tested on tissue for saftey, long term trials on humans are needed to determine side effects,
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They have to develop alternate compounds to try and reduce side effects, recommended dose has to be proven to be effective, research has to be indepentantly verified, patents expire before costs are recouped allowing others to make similar products
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What is an allotrope?
They are different structures of the same element
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Name three allotropes of carbon
Diamond, graphite, and fullerenes
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What structure do fullerenes take on and what are they used for?
They form spheres or tubes and are often used to carry and deliver drug molecules around the body, and to trap dangerous substances in the body and remove them.
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How many carbon atoms does buckminsterfullerene contain?
60 carbon atoms in a sphere. C60
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How is diamond so strong?
Because each bond is covalent and they are all in different directions
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How are the carbon atoms formed in graphite?
They are in layers
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Why is graphite used in pencils and as lubricant?
Because the layers can slide over eachother
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Why is the melting point of diamond so high?
Because all the bonds are strong covalent bonds, which means a lot of energy is needed to break them.
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Why doesn't diamond conduct electricity?
Becasue it has a lack of free electrons
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Why can graphite conduct electricity?
Because it contains delocalised electrons
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What can nanotubes be used in?
Catalyst systems
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Other cards in this set

Card 2


What usually happens to the rate of a reaction as it progresses, and why?


They are usually fast at the start and then slow down as the reactants are used up

Card 3


How can the rate of reaction be worked out?


Preview of the front of card 3

Card 4


What is the formula for gradient?


Preview of the front of card 4

Card 5


What is the limiting reactant?


Preview of the front of card 5
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