C3

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  • Created by: ireynolds
  • Created on: 25-04-17 12:00
What's an exothermic reaction?
A reaction which gives out energy to the surroundings, usually in the form of heat, which is shown by a rise in temperature.
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What's an endothermic reaction?
It's a reaction which takes in energy from the surroundings, usually in the form of heat, which is shown by a fall in temperature.
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Give an example of an exothermic reaction?
Burning fuels (combustion) you can tell as it gives out a lot of heat.
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Give an example of an endothermic reaction?
Thermal decomposition. (heat must be supplied to the compound to decompose)
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How can you measure the amount of energy released by a chemical reaction?
By taking the temp of the reactants, mixing them in polystrene cup(insulator) and measuring them temp of the solution at the end of the reaction.
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What kind of reaction is adding an acid to an alkali?
Exothermic.
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What kind of reaction is dissolving ammonium nitrate in water?
Endothermic, as it results in drop of temperature.
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Why is bond breaking an endothermic process?
Because energy must be supplied to break existing bonds. And opposite for creating new bonds.
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In an exothermic reaction, what releases the most energy?
The energy released in bond formation is greater than the energy used in breaking old bonds.
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What's the SHC of water?
4.2J/g/c
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How do you use SHC to calculate energy transferred?
By heating water using a liquid fuel. If you measure how much fuel you've burned and the temp change of the water, you can work out how much energy is supplied by each gram of fuel.
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How can you reduce heat loss during the experiment?
Use screen as a draught excluder. Insulating lid. Copper calorimeter.
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How do you calculate the mass of fuel burned?
By subtracting the final mass from the initial mass.
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How can you make it a fair test?
Everything except the fuel used should be the same, apparatus, amount of water, and temp of the water.
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What is the rate of a chemical reaction?
How fast the reactants are changed into products, and the reaction is over when all the reactants are used up.
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Examples of slow reactions?
Rusting of iron, and chemical weathering.
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What's an example of a moderate speed reaction?
Metal reacting with dilute acid to produce a gentle stream of bubbles.
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What are examples of fast reactions?
Burning and explosions.
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In what two ways can you do an experiment to follow a reaction?
By measuring how quickly gas is produced. 1) Measure the change in mass, on a balance. 2) Measure the volume of gas given off, using a gas syringe.
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Explain collision theory?
That the rate of a chemical reaction depends on; the collision frequency of reacting particles, and the amount of energy transferred during a collision.
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What is a successful collision?
One that ends in the particles reacting to form products.
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What is limiting reactant?
The reactant that's totally used up. Once it's used up the reaction can't continue.
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What factors does rate of reaction depend on?
Temperature, concentration (or pressure), presence of a catalyst and size of the particles.
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How does more collisions increase the rate of reaction?
Because reactions happen if particles collide, so if the number of collisions is increased, the reaction happens more quickly.
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How does higher temperature increase the rate of reaction?
When the temperature is increased the particles move quicker, and have more collisions. Also, the energy of collisions will increase as they're moving faster, so they'll be more successful collisions.
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How does higher concentration increase the rate of reaction?
As if a solution is more concentrated, there are more reactant particles in the same volume, therefore collisions are more likely. Same with gas and pressure.
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How does increasing the surface area increase the rate of reaction?
Smaller pieces = larger surface area = particles have more area to work on, and collision frequency will increase.
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How does a catalyst increase the number of successful collisions?
Catalyst is a substance which increases the speed of a reaction. It increases it by providing a surface for the reacting particles to stick to and collide, and reduces the energy needed to successfully collide. Increasing the number of successful col
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What do reaction rate graphs show?
Rate of reaction data.
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What is the relative atomic mass?
The number on the top.
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What is the relative formula mass?
All of relative atomic masses in an element added together.
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How do you find the relative formula for a compound with brackets in?
Expand the brackets (by the number outside the bracket), then calculate the relative formula mass normally.
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What is conserved mass in a chemical reaction?
No atoms are destroyed or created in a chemical reaction. There's the same number and types of atoms on each side of a reaction equation, due to this no mass is gained or lost.
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What's the method for calculating masses in reactions?
1) Write out the balanced equation. 2) Work out the relative formula mass for the compounds you need. 3) Divide to get 1, then multiply to get all.
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What is atom economy?
% of reactants changed to useful products. The atom economy of a reaction tells you how much of the mass of the reactants is wasted when manufacturing a chemical.
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What's the equation for atom economy?
atom economy= total relative formula of desired product/ total relative formula of all products.
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What does 100% atom economy mean?
All the atoms in the reactants have been turned into useful products. The higher the atom economy... the greener the process.
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What's the method for working out % atom economy?
1) Identify the useful product 2) Work out the relative formula of all the products, and the useful products. 3) Use the formula to calculate the atom economy.
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Problems with reactions with low atom economy?
Use up resources quickly. Make lot's of waste materials which have to be disposed of. Unsustainable. Not profitable. You have to find uses for the waste products.
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How can you calculate the percentage yield of an equation?
From the balanced reaction equation.
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What's the formula for percentage yield?
Actual yield (grams)/predicted yield (grams) x100
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Why do industrial processes want a high percentage yield?
Reduce waste & reduce costs.
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What are the 4 main ways percentage yield go down?
Evaporation, not all reactants react to make a product, filtration & transferring liquids.
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How does evaporation decrease yield?
As they evaporate all the time, especially when heated.
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How does not all reactants react to make product decrease yield?
As in reversible reactions the products can turn back to reactants, so the yield will never be 100%. E.G; the Haber process.
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How does filtration reduce percentage yield?
As when you filter a liquid to remove particles you always lose some product, even if you're really careful.
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How does transferring liquids decrease percentage yield?
Always lose liquid when transferring it from one container to another, it's left on the inside surface.
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What is batch production?
It only operates at certain time.
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Why is batch production used for pharmaceutical drugs?
They're complicated to make and have a low demand, cost-effective as flexible, start-up costs are relatively low.
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Disadvantages of batch production?
It's labour-intensive and it's tricky to keep the same quality batch to batch.
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What's continuous production?
It runs all the time.
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Why do large-scale industrial manufacturers of popular chemicals use continuous production?
It never stops so no time wasted emptying it and setting it up, runs automatically, quality of product is consistent.
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Disadvantages of continuous production?
Start-up costs are huge, not cost-effective unless run at full capacity.
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Why do pharmaceutical drugs often cost a lot?
Research and development, trailling, manufacture.
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Why does research and development of a pharmaceutical drug cost a lot?
As it involves finding a suitable compound, testing it, modifying it and needs lots of work of highly paid scientists.
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Why does trailling of a pharmaceutical drug cost alot of money?
Time-consuming tests, animal traills, human traills, and the manufacturer has to prove the drug meets legal requirements and works safely.
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Why does the manufacture of a pharmaceutical drug cost a lot of money?
As it's a multi-step batch production which is labour intensive and can't be automated. Energy and raw-materials costs, sometimes rare materials that need to be extracted.
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How do you extract a substance from a plant?
1) crush the plant 2) boil to dissolve in a suitable solvent 3) separate by chromatography 4) extract the chemical wanted.H
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How can you test for purity by chromatography?
Pure substances wont be separated and will move as one blob.
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How can you test for purity by boiling?
Pure substances have a specific melting point and boiling point (E.G; water is 100c) and impure substances will have incorrect boiling and melting points.
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What is an allotrope?
Different structural forms of the same element in the same physical state E.G; all solids.
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What properties of diamond make it ideal for jewellery?
Lustrous (sparkly) and colourless.
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Why are diamond ideal as cutting tools?
As they're really hard, and has a very high melting point.
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Why are diamonds really hard?
Each carbon atom forms four covalent bonds in a very rigid giant covalent structure, making them really hard.
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Why do diamonds have a very high melting point?
As the strong covalent bonds take a lot of energy to break.
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Why don't diamonds conduct electricity?
Has no free electrons or ions.
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What are the visual properties of graphite?
Black,opaque but still shiny.
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What's the structural form of graphite?
Each carbon atom only forms 3 covalent bonds, creating sheets of carbon atoms which are free to slide over eachother.
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Why is graphite ideal for pencils and lubricating material?
Layers are held together weakly so they are slippery and can be rubbed off.
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Is graphite's melting point high or low?
high; it needs lot's of energy to break the covalent bonds.
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Why can graphite conduct electricity?
As only 3 out of each carbons 4 outer electrons are used in bonds, so there's lot's of delocalised electrons free to move.
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Why can carbon form giant molecular structures like diamond and graphite sheets?
Because carbon can form lots of covalent bonds with itself.
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What properties do all the covalent bonds give giant molecular structures?
Strong, high melting points, don't dissolve in water.
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Why don't giant molecular structures usually conduct electricity?
No free electrons or ions (graphite is an exception)
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What are fullerenes?
Molecules of carbon shaped like closed tubes or hollow balls.
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How can fullerenes be used to deliver and slow-release drugs into the body?
As they can be used to cage other molecules, as they can form around another atom or molecule, and it's trapped inside.
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What are nanotubes?
Fullerenes can be joined together to form them; tiny hollow tubes.
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Why can nanotubes be used to help make industrial catalysts?
As they have a huge surface area and the individual catalyst molecules could be attached to the nanotubes.
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Other cards in this set

Card 2

Front

What's an endothermic reaction?

Back

It's a reaction which takes in energy from the surroundings, usually in the form of heat, which is shown by a fall in temperature.

Card 3

Front

Give an example of an exothermic reaction?

Back

Preview of the front of card 3

Card 4

Front

Give an example of an endothermic reaction?

Back

Preview of the front of card 4

Card 5

Front

How can you measure the amount of energy released by a chemical reaction?

Back

Preview of the front of card 5
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