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Chemistry > Extracting Metals And Electrolysis > Flashcards

Extracting Metals And Electrolysis Flashcards

1
Q

What happens if the metal is less reactive then hydrogen?

A

It will not displace hydrogen so there will be no reaction
It will also not displace water or acid as it cannot displace the hydrogen within the compound so won’t react with dilute acid

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2
Q

What is bioleaching?

A
  • uses bacteria to separate substance which gets energy from the bonds between atom in the ore separating out the metal from the ore in the process
  • this process leaves leachate solution containing metal ions which can be extracted through electrolysis of displacement with more reactive metal
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3
Q

What are some advantages of bioleaching?

A
  • energy efficient
  • gets copper from low grade ores increasing potential copper reserves
  • not as expensive
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4
Q

What are some disadvantages of bioleaching?

A

Slow process as takes a long time for plants to grow

-only removes toxic copper from surface layer as roots can only penetrate this far

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5
Q

What is phytoextraction?

A

This involves growing plants in soil that contain metal compounds. These plants are then harvested, dried or burned in a furnace. This leaves the metal amongst other impurities which can then be extracted by electrolysis or displacement reactions

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6
Q

What are some advantages of phytomining?

A
  • can get metal (copper) from low grade ores
  • growing plants is cheap
  • plants provide oxygen and reduce carbon dioxide
  • faster then bioleaching
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7
Q

What are some disadvantages of phytomining?

A
  • not energy efficient
  • costs a lot of money
  • produces CO2 through burning
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8
Q

What are some advantages of recycling metals?

A
  • environmentally mines are damaging so we now don’t need as many
  • cuts down the amount if rubbish sent to landfills
  • conserves energy and resources
  • we can preserve rare materials
  • economically viable
  • huge industry so creates lots of jobs
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9
Q

What are some disadvantages of recycling metals?

A

The collection and sorting lot of metals is time consuming and still needs energy

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10
Q

What is a life cycle assessment?

A

Looks at the stage of life of a product. It works out the potential environmental impacts at each stage

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11
Q

What is stage 1 of a life cycle assessment?

A

How metals are extracted

E.g. have to be mined and extracted from ores where lots of energy is needed causing pollution

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12
Q

What is stage 2 of a life cycle assessment?

A

Manufacturing products uses a lot of energy causing pollution and also how to dispose of waste products
-e.g. most chemical manufacture need water so businesses must ensure they don’t put polluted ware back into the environment at the end of the process

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13
Q

What is stage 3 of a life cycle assessment?

A

How using the product may damage the environment

Paint gives off harmful toxins, burning fuels releases gg gases, fertilisers can leach into ecosystems

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14
Q

What is stage 4 of a life cycle assessment?

A

How the product is disposed of

  • Often landfill sites that take up space and pollute surroundings
  • Products also be incinerated which causes land pollution
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15
Q

What is electrolysis?

A

The breaking down of a compound using electricity. This happens in ionic compounds when they are molten or dissolved causing the electrolyte to decompose

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16
Q

Why must a the ionic substance be molten or dissolved ?

A

As it allows the bonds to break, which then means the ions can move freely when voltage is applied

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17
Q

What is the ionic compound broken down into?

A

Positive cations and negative anions

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18
Q

What is a cathode?

A

A negative electrode which attracts positive cations e.g. metals

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19
Q

What is an anode?

A

A positive electrode which attracts negative anions e.g. non-metals

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20
Q

What is an electrode?

A

Solids that conduct electricity

21
Q

What is an electrolyte?

A

An liquid that can conduct electricity and carries the charge

22
Q

Why might a student carry out electrolysis in a fume cupboard?

A

As the gases given off may be toxic

23
Q

What are spectator ions?

A

Ions which do not gain or loose electrons

24
Q

What happened at the negative cathode?

A

A positive cation is discharged as it is reduced/ gains electrons to become a neutral atom

25
Q

What happens at the positive cathode?

A

A negative anions is discharged as it is oxidised/deposits electrons to become a neutral atom

26
Q

How do you set up the method of electrolysis of copper sulphate with graphite electrodes?

A
  • Fill a beaker with copper sulphate solution with graphite electrodes -making sure the circuit is complete
  • add the negative cathode and positive anode to the solution
27
Q

What is the outcome of electrolysis of copper sulphate with graphite electrodes?

A

At the cathode copper is made as copper is less reactive than hydrogen (covered in an orange metallic substance)
At the anode oxygen and water are produced so you should see bubbles

28
Q

What happens if the cation is more reactive than hydrogen?

A

Hydrogen gas will be made at the cathode

29
Q

What happens to the cathode during the electrolysis of copper sulphate with copper electrodes?

A

It gets heavier as copper ions are discharged (reduced) and form pure copper metal which is deposited on the cathode. When the current is higher the electrons are provided more quickly

30
Q

What happens to the anode during the electrolysis if copper sulphate with copper electrodes?

A

The anode gets lighter as the impure copper atoms give away electrons (oxidised) and form copper ions which dissolve in the solution. When the current is higher the electrons are removed more quickly

31
Q

What is the half equation for the cathode in the electrolysis if copper sulphate with copper electrodes

A

Cu2+ + 2e- —> Cu

Reduction happens because electrons are gained

32
Q

What is the half equation for the anode in the electrolysis if copper sulphate with copper electrodes

A

Cu - 2e- —> Cu2+

Oxidation happens as electrons are lost

33
Q

When an ionic compound is dissolved in water why is the electrolysis different?

A

As there is also H+ ions and OH- ions from the water

34
Q

What are the electrolysis rules for the cathode?

A

If the metal carbon is more reactive than hydrogen the metal stays in the solution and hydrogen is made
If the metal is less reactive then hydrogen then a metal is made

35
Q

What are the electrolysis rules for the anode?

A
  • if the non metal anion is a halide (Cl-, Br-, I-) then the halogen molecule is made
  • if the non-metal ion is a sulphate then oxygen is made because the OH-ions form water which decomposes to oxygen and hydrogen
36
Q

What does a sulphate make at the anode?

A

Oxygen

37
Q

What does sodium make at the cathode?

A

Hydrogen

38
Q

What is oxidation and reduction?

A
  • Oxidation is the gain of oxygen, reduction is the loss of oxygen
  • oxidation is the loss of electrons, reduction is the gain of electrons
39
Q

What is the reactivity series and what does it show?

A

The reactivity series is a table that lists metals in order of their reactivity yet often includes carbon and hydrogen

  • a metals position compared to carbon dictates how its extracted from its ores
  • hydrogen can be included to show the reactivity of metals with dilute acids, it it is below hydrogen it is less reactive so won’t react with dilute acids
39
Q

What is the trend in the reactivity series?

A

-metals at the top are the most reactive so easily loose their electrons to form cations and are easily oxidised (vice versa for the bottom

39
Q

How does reacting a metal with acid show it’s reactivity?

A

Metal + water — metal hydroxide + hydrogen

-more reactive metals will react vigorously with cold water but less reactive ones will only react with steam

39
Q

How does reactive metals with dilute acid shows its reactivity?

A
  • the more reactive metals will have faster reactions with the acid so form bubbles quicker
  • very reactive metals will fizz vigorously and less reactive ones will only bubble slightly. Some like copper won’t react at all
  • test for a squeaky pop
39
Q

What is a metal ore?

A

A rock which contain enough metal to make it economically worthwhile to extract (in many cases the ore is an oxide of the metal)
-most metals are found in ores in the earth’s crust and are then extracted from the ores, unreactive metals are found in ores as uncombined elements but are still usually refined

39
Q

How can a metal be extracted from its ore?

A

Chemically by reduction using carbon through heat

  • when the ore is reduced oxygen is removed (e.h. Iron oxide + carbon — iron - carbon dioxide)
  • metals below carbon in the reactivity series can be extracted by this, as carbon can only take away the oxygen from metals that are less reactive than itself
39
Q

How are metals that are more reactive than carbon extracted?

A
  • using electrolysis of molten compound
  • once the metal ore is melted an electric current is passed through it, the metal is discharged at the cathode and the non metal at the anode
39
Q

What is an example of electrolysis to extract metal?

A

Aluminium using carbon electrodes

  • It has a high melting point so is first dissolved in molten cryolite to lower the melting point. The ions in this molten mixture are free to move
  • aluminium forms at the cathode (Al3+ + 3e- — Al)
  • oxygen is formed at the anode (2O2- — O2 + 4e-
39
Q

What are the drawbacks of electrolysis?

A

You need large amount of electricity which is expensive

  • there are also costs associated with the melting/dissolving the metal ore so it can conduct electricity
  • extracting metals using carbon is much cheaper and acts as a fuel to provide the heat
  • cheaper to extract less reactive metals than more reactive ones
39
Q

How do you write half equations?

A
  • they show how electrons are transferred in a reaction
  • pout on of the things being oxidised or reduced on one side of the arrow and he thing getting the opposite done on the other
  • balance the numbers like a normal equation
  • then add electrons on to one side to balance up the charges

Chemistry (12 decks)

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