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Chemistry > C3 > Flashcards

C3 Flashcards

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1
Q

What is an exothermic reaction?

A

One which gives out energy usually in heat

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2
Q

How is an exothermic reaction shown?

A

A rise in temperature

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3
Q

What is an example of an exothermic reaction?

A

Combustion

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4
Q

What is an endothermic reaction?

A

One that takes in energy, usually in heat

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5
Q

How is an endothermic reaction shown?

A

A fall in temperature

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6
Q

What is an example of an endothermic reaction?

A

Thermal decomposition

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7
Q

How do you decide whether a reaction is endo or exo?

A

You can measure the amount of energy produced by taking the temperature of the reactants and mix in a polystyrene cup and measure the temperature of the solution at the end

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8
Q

What happens during a chemical reaction?

A

Old bonds are broken and new bonds are formed

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9
Q

Is bond breaking an exothermic or an endothermic reaction?

A

Endothermic because energy is supplied

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10
Q

Is bond making an exothermic or an endothermic reaction?

A

Exothermic because it releases energy when formed

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11
Q

Explain the calorimetric method ued to measure the energy content of fuels

A
  1. Reduce draughts so as much heat as possible goes into heating the water eg. use a screen
  2. Put fuel in spirit burner and weigh
  3. Measure water into a copper calorimeter
  4. Take initial temperature of water and light wick
  5. When water temperature has raised by 20?30 degrees, note the highest temperature of water
  6. Reweigh the burner
  7. Repeat if comparing fuels
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12
Q

What is the equation for energy given out per gram?

A

Energy per g = energy released / mass of fuel burnt

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13
Q

Name 4 ways to keep the calorimetric test fair

A

Same equipment
Same amount of water
Water initial and final temperatures = same
Repeat

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14
Q

Give an example of a slow chemical reaction?

A

Rusting

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15
Q

Give an example of a fast chemical reaction?

A

Burning

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16
Q

The rate of reaction that produces a gas can be observed by measuring how quickly the gas is produced. Name two ways of doing this.

A

? Measure the change in mass = mass falls as gas produced
? Measure cm(cubed) of gas given off = gas syringe

Must do these at regular intervals

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17
Q

What two things does the rate of reaction depend on?

Explain why

A

Collision frequency = more collisions = faster

Energy transferred in collision = enough energy to be successful

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18
Q

What effect does an increase in temperature have on collisions?

A

They move quicker = more collisions

Increases energy of collisions = more successful collisions

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19
Q

What effect does an increase in concentration or pressure have on collisions?

A

More particles in the same space = closer together = more collisions

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20
Q

What effect does an increase in surface area have on collisions?

A

More surface area exposed = more area to work on = collisions will increase

21
Q

What effect does a catalyst have on collisions?

A

Provides surface where reactions can take place.

Lowers the activation energy (reduces the energy needed by particles to react)

22
Q

What is the equation for atom economoy?

A

Atom economoy = Total Mr of desired products / Total Mr of all products (x100)

23
Q

Why does a high atom economy benefit the environment?

A

Reactions with low atom economy use up resources very fast

Make lots of waste = has to be disposed of = unsustainable

24
Q

How does atom economy effect profits?

A

The lower the atom economy = aren’t profitable because expensive to buy materials and waste products can be expensive to dispose responsibly of

25
Q

What is the equation for percentage yield?

A

Percentage yield = actual yield (g) / predicted yield (g)

x100

26
Q

Give four reasons for why yields are always less than 100%?

A

? Evaporation
? Filtration (solid/liquid some left behind)
? Transferring liquids (some remain on inside of old container)
? Not all reactants make a product

27
Q

Give 2 advantages of batch production

A

Flexible = several different products made using the same equipment
Low start up costs

28
Q

Give 2 disadvantages of batch production

A

Labour intensive

Difficult to obtain the same quality in each batch

29
Q

Give 3 advantages of continuous production

A

Never stops = no time is wasted emptying reactors and setting up again
Runs automatically
Quality is always consistent

30
Q

Give a disadvantage of continous production

A

Start up costs are very high

31
Q

Give an example of a product made by batch production

A

Pharmaceutical drugs

32
Q

Give an example of a product made by continous production

A

Ammonia (haber process)

33
Q

What is the pharmaceutical drug making process?

A

? Research and development
? Testing/trialling to ensure it works and is safe
? Manufacture

34
Q

What two things make drugs expensive to make?

A

? Raw materials (extracted from plants)

? Energy

35
Q

How do you extract a substance from a plant?

A

It has to be crushed, boiled and dissolved in a suitable solvent
Then use chromatography to extract the substance you want

36
Q

How can you tell if a substance is pure with chromotography?

A

It won’t be seperated by chromotography (one blob)

37
Q

How can you tell if a substance is pure by the boiling/melting points of thesubstance?

A

They have specific melting points

If a substance is impure, the melting point will be too low and the boiling point too high

38
Q

Give four properties of diamond

A

Lustrous
Colourless
Strong covalent bonds = high melting point
Doesn’t conduct electricity

39
Q

What makes diamond very hard?

A

Each carbon atom forms four covalent bonds in a very rigid giant covalent structure = very hard

40
Q

Why is diamond useful as a cutting tool?

A

?Really hard because of giant covalent structure

?Has a high melting point

41
Q

Give five properties of graphite

A 
Black
Opaque
Shiny
High melting point
Conducts electricity
42
Q

Explain the structure of graphite

A

Each carbon atom only forms three covalent bonds, creating sheets of carbon atoms which are free to slide over each other

43
Q

Why can graphite conduct electricity?

A

Since only 3 out of each carbons 4 outer electrons are used in bonds, there are lots of delocalised electrons which move

44
Q

What three properties do all giant molecular structures share?

A

Strong, high melting points and don’t dissolve in water

45
Q

What are fullerenes?

A

Molecules of carbon shaped like closed tubes/hollow balls

46
Q

What is a use of a fullerene?

A

To cage” other moleculs = eg. new way of delivering a drug to the body for slow release?”

47
Q

What can fulluerenes be joined together to make?

A

Nanotubes which are tiny hollow carbon tubes

48
Q

What is a use of a nanotube?

A

Have a large surface area = industrial catalysts

Chemistry (8 decks)

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