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Chemistry > PAPER 2 > Flashcards

PAPER 2 Flashcards

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1
Q

Collision theory

A

Chemical reactions can only take place when the reacting particles collide with each other. The collisions must have sufficient energy

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2
Q

What does frequency mean in terms of collision theory?

A

The number of successful collisions per second

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3
Q

Activation energy

A

The minimum amount of energy that the particles must have in order to react (ie collide successfully)

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4
Q

why does increasing temperature increase the rate of reaction

A

Because it increases the energy of the particles. Because of this, they can move faster which increases the frequency of collisions. Also, each collision has more energy meaning that more particles can overcome the activation barrier and collide successfully

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5
Q

What does a catalyst do?

A

Increases the rate of chemical reactions- by providing a different pathway for the reaction that has a lower activation energy (which means that more particles can successfully collide per second) but are not used up during the reaction. This allows us to carry out reactions quickly without needing to increase the temperature. (Saves money)

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6
Q

How can you change the direction of reversible reactions?

A

Changing the conditions

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7
Q

General formula for Alkanes

A

CnH2n+2

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8
Q

What is the complete combustion of methane?

A

CH4 + O2 –> CO2 + H2O

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9
Q

How how many bonds do alkanes have between the carbon atoms?

A

Single covalent bonds

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10
Q

How many bonds do alkenes have between two carbon atoms?

A

double covalent bonds

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11
Q

Why are alkenes useful?

A

They are used to make polymers, used as the starting material for other useful chemicals as well.

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12
Q

Describe when key fact with the difference between alkanes and alkenes (apart from the bonds)

A

Alkenes are more reactive than alkanes

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13
Q

How do you test for Alkenes?

A

Put alkene and bromine water (orange) into a test tube. If you shake it, the bromine water turns colourless.

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14
Q

Give two properties of a pure substance?

A

They melt at a specific fixed temperature and also has a specific fixed boiling point (impure substances melt and boil over a range of temperatures).

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15
Q

Give two properties of a pure substance?

A

They melt at a specific fixed temperature and also has a specific fixed boiling point (impure substances melt and boil over a range of temperatures).

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16
Q

What is a formulation?

A

A complex mixture that has been designed as a useful product

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17
Q

In a formulation, why is the quantity of each component carefully measured?

A

So that the product has the properties we need

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18
Q

All separation techniques including paper chromatography are what type of process?

A

Physical (do not involve chemical reactions and no new substances are made)

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19
Q

What must you do to successfully carry out chromatography

A
  1. Use a ruler to draw a horizontal pencil line on the chromatography paper which should be 2cm from the bottom of the paper.
  2. Mark five pencil spots at equal spaces across the line. Leave at least 1 cm clear at each side.
  3. Use a capillary tube (very thin glass tube) to put a small spot of each unknown food colours and the unknown colour onto the pencil spots.- important to keep the spots small as it prevents the colours spreading into each other later.
  4. Pour water into a beaker to a depth of 1cm.- in this case, the water is the solvent
  5. Attach the paper to a glass rod using tape and lower the paper into the glass beaker.- the bottom of the paper should dip into the water.
    The pencil line with the spots of ink must be above the surface of the water otherwise the water will wash the ink off the line.
    The sides of the paper must not touch the side walls of the beaker.- is that does happen. then it will interfere with the way that the water moves
  6. Put a lid on the beaker to reduce evaporation of the solvent
  7. Remove the paper when the water has travelled around three-quarters up the paper.
  8. Use a pencil to mark the point where the water reached
  9. Hang the paper up to dry.
  10. Next if you want you can identify the chemical in these colours. To do that, we have to calculate the rf values.
    To do this you, measure the distance from each pencil line to the centre of each spot. then you measure the distance moved by the water from the pencil line. Then to calculate it you do the equation-
    Distance moved by the chemical/ distance moved by solvent.- answer will be below 1 (they do not have a unit)
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20
Q

What do we call the paper in chromotography?

A

The stationary phase because it does not move.

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21
Q

What do we call the solvent in chromatography?

A

The mobile phase because it does move

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22
Q

Why doe paper chromatography work?

A

Because each chemical in the mixture will be attracted to the stationary phase (the paper) to a different extent.
- Chemicals that are strongly attracted to the stationary phase will not move very far and vice versa with weak chemical

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23
Q

How many spots will a pure chemical produce in chromatography.

A

A single spot in all solvents. A chemicals in a mixture may separate into different spots depending on the solvent

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24
Q

What does the atmosphere of Earth today contain?

A

80% Nitrogen
20% Oxygen
(Co2, H2O, Ar) 0.04%

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25
Q

What did the early atmosphere contain?

A

mostly (95%) Co2

N2, NH3 (ammonia), CH4 (Methane), H2)

26
Q

what happened to cause the early atmosphere to change to the atmosphere today?

A
  • During the first billion year, there was intense volcanic activity why released water vapour and nitrogen and CO2
  • As the earth cooled, the water vapour condensed to form the oceans.
  • Some of the carbon dioxide dissolved in the oceans to form a weak acid and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere .
  • Next algae formed which produced oxygen and reduced CO2. Over the following billion years, plants evolved further decreasing CO2 in the atmosphere and at some point.
  • Also, carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon
27
Q

How is coal formed?

A

Its formed from the remains of ferns and trees. If these die in marshy wetlands then they do not decompose due to the lack of oxygen or acidic conditions which both prevent bacteria from carrying out decomposition. Over time, the plant remains are covered with sediment and are compressed. High temperature and pressure creates coal.

28
Q

How is crude oil formed?

A

They are formed from plankton. When these die, they settle in mud on the sea-bed. If oxygen is not present, they do not decompose. Over time, they are compressed by sediment and heat and pressure converts them into crude oil.

29
Q

Does is it mean if something is finite?

A

They cannot be replaced as quickly as they are being used.

30
Q

How is sewage treated?

A
  1. Screening and grit removal.
  2. Sedimentation to produce sewage sludge and effluent.
  3. Anaerobic digestion of sewage sludge
  4. Aerobic biological treatment of effluent.
31
Q

What does drinking water must not have?

A
  1. It must have low levels of dissolved salts.

2. Cannot have high levels of microbes such as bacteria

32
Q

How do you get potable water from groundwater?

A
  1. Filtered

2. Sterilised

33
Q

How do you get potable water from sea water?

A
  1. Desalination (removing salt)
    or
  2. Reverse osmosis
34
Q

Describe the process in Phyto-mining

A
  • Plants are grown on land containing the metal compound that we want.
  • These plants absorb the metal compound we want and they concentrate it in their tissue.
  • The plants are then harvested and burned.
  • At the end, the ash contains a relatively high concentration of the metal compound.
    -Now you need to extract the metal from the compound, in the case of copper compounds we can displace the copper using iron as iron is more reactive than iron and usually scrap iron is used which is relatively cheap.
    You can also extract it using electrolysis.
35
Q

Describe the process of bioleaching.

A
  • Bacteria are mixed with the low grade ore.
  • The bacteria carry out chemical reactions and they produce a solution called a leachate which contains the metal compound that we want.
  • Now you need to extract the metal from the compound, in the case of copper compounds we can displace the copper using iron as iron is more reactive than iron and usually scrap iron is used which is relatively cheap.
    You can also extract it using electrolysis.
36
Q

Equation for butane

A

C4H10

37
Q

Equation for ethane

A

C₂H₆

38
Q

Equation for methane

A

CH₄

39
Q

Equation for propane

A

C₃H₈

40
Q

Equation for Alkenes

A

CnH2n

41
Q

Test for hydrogen

A

Burning splint at open end of test tube of gas. Squeaky pop

42
Q

Test for oxygen

A

Glowing splint inserted into test tube. The splint relights in oxygen

43
Q

Test for carbon dioxide

A

When CO2 is shaken with or through limewater, the limewater turns cloudy

44
Q

Test for chlorine

A

When damp litmus paper is put into chlorine gas- the litmus paper is bleached and turns white

45
Q

Carbon footprint

A

Total amount of CO2 and other greenhouse gases emitted over the full cycle of a product, service, event or person

46
Q

What is the test for pure water?

A

Boil and the result is that it boils at 100c

47
Q

What does a sustainable environment mean?

A
  1. Meets the needs of the current generation

2. Without comprising needs of future generations

48
Q

What would happen when the concentration of a product is decreases.

A

more reactants will

react until equilibrium is reached again.

49
Q

What is Crude oil

A

the remains
of an ancient biomass consisting mainly of plankton that was buried
in mud.

50
Q

During combustion, what happens to the carbon and hydrogen in the fuels

A

They are oxidised

51
Q

What is a pure substance?

A

a single element or compound,

not mixed with any other substance.

52
Q

Name the green house gases

A

Water vapour, carbon dioxide and

methane

53
Q

What are the affects of climate change?

A
  1. Increase melting of ice caps

2. More severe weather

54
Q

What is a hypothesis

A

A proposal that could explain a fact or an observation- a hypothesis must be testable

55
Q

Describe the two practicals which find the affect of concentration on rate of reaction

A
  1. Use a measuring cylinder to put 10cm^3 of sodium thiosulfate solution into a conical flask.
  2. Place the conical flask onto a printed black cross.
  3. Add 10cm^3 of hydrochloric acid into the conical flask.
  4. Swirl the solution and start a stopwatch
  5. Look down through the top of the flask and after a certain time, the solution will turn cloudy.
  6. Stop the clock when we can no longer see the cross.
  7. Carry out the experiment again using lower concentrations of sodium thiosulfate solution
  8. Repeat the whole whole experiment and calculate mean values for each concentration of sodium thiosulfate solution.

OTHER METHOD

  1. Use a measuring cylinder to place 50cm^3 of hydrochloric acid into a conical flask.
  2. Attach the conical flask to a bung and delivery tube.
  3. Place the delivery tube into a container filled with water.
  4. Place an upturned measuring cylinder also filled with water over the delivery tube.
  5. Add a 3cm strip of magnesium to the HCl and start a stopwatch.
  6. Reaction produces hydrogen gas and is trapped in the measuring cylinder. And every 10 seconds we measure the volume of hydrogen gas in the measuring cylinder and we continue this until no more hydrogen is given off.
  7. Repeat the experiment using difference concentrations of hydrochloric acid
56
Q

How does paper chromatography separates substances?

A

Solvent moves up and carries different distances depending on their solubility in the solvent and it’s attraction to the paper

57
Q

What is a solvent

A

the substance that does the dissolving

58
Q

What is a solute

A

substance that dissolves to make a solution

59
Q

What does solubility mean?

A

a measurement of how much of a substance will dissolve in a given volume of a liquid

60
Q

Why are life cycle assessments fome?

A

To assess environmental impact

61
Q

Describe how oxides of nitrogen are produced in a car engine

A

High temps enable oxygen and nitrogen to react

Chemistry (3 decks)

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