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Chemistry OCR B Alevel > Developing Metals > Flashcards

Developing Metals Flashcards

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1
Q

Describe how you would do a manganate(Vii) titration?

A

Measure out a quantity of reducing agent-Fe2+ with a pippette and put in conical flask

Add sulfuric acid (in excess)

Add MnO4- using a burette and swirl flask

When turns pink all reducing agent has been used up

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2
Q

What shape are complexes with 4 coordinate bonds and what angles?

A

Square planar-90

Tetrahedral-109.5

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3
Q

Which electrode does oxidation occur?

A

Anode(positive)

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4
Q

Which electrode does reduction occur?

A

Cathode(negative)

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5
Q

In drawings of electrochemical cells which way round should the electrodes be?

A

Anode on the left and cathode on the right

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6
Q

How do you measure the Ecell?

A

More positive standard electrode potential- more negative standard electrode potential

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7
Q

How do you make a full reaction equation for a cell?

A

The more positive half equation goes forward and more negative goes back

Must equalise the electrons

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8
Q

Name 3 ways you can prevent rusting?

A

Painting with a polymer

Oiling/greasing

Sacrificial metal

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9
Q

State the 4 steps of rusting

A

Fe reacts with water and oxygen to make Fe2+ and OH-

Fe2+ + 2OH- ——-> Fe(OH)2

Reacts with water and oxygen
To make Fe(OH)3

Gradually turns into Fe2O3•H20

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10
Q

5 properties I’d transition metals

A

More than one stable ions

Ions have incomplete d orbitals

Formation of complexes

Formation of coloured ions

Ability to act as homogeneous or heterogeneous catalysts

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11
Q

What colour is Fe2+

A

Pale green

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12
Q

What colour is. Fe3+?

A

Yellow

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13
Q

What colour is Cu2+?

A

Blue

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14
Q

What colour is Cu+?

A

Colourless

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15
Q

Show Fe2+ in water complex

A

|Fe(H2O)6|2+

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16
Q

Show Fe3+ complex in water

A

|Fe(H2O)6|3+

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17
Q

Show Cu2+ complex in water

A

|Cu(H2O)6|2+

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18
Q

Show Cu2+ complex with ammonia

A

Cu(NH3)4 2+

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19
Q

Show complex of Cu2+ with chlorine

A

CuCl4 2-

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20
Q

What do you call a ligand with 2 lone pairs?

A

Bidentate

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21
Q

What is a coordinate bond?

A

Daitive covalent

22
Q

What is ethandioate?

A

A bidentate Ligand

23
Q

What colour is

|Cu(H2O)6|2+?

A

Blue solution

24
Q

what colour is Cu(OH)2?

A

Pale blue precipitate

25
Q

What colour is

|Cu(NH3)4|2+?

A

Deep blue

26
Q

What colour is |CuCl4|2-?

A

Yellow

27
Q

What colour is

|Fe(H2O)6|2+?

A

Green solution

28
Q

What colour is Fe(OH)2

A

Dirty green precipitate

29
Q

What colour is

|Fe(H2O)6|3+?

A

Yellow solution

30
Q

What colour is Fe(OH)3?

A

Orange precipitate

31
Q

What can transition metals act as homogeneous catalysts?

A

They have variable oxidation states

32
Q

Why can transition metals act as heterogeneous catalyst?

A

Transition metals use D and S subshell electrons to form weak bonds to the reactants

33
Q

Why are complexes coloured?

A

The Ligands cause d orbitals to split resulting in an energy gap
Electrons absorb light frequencies that match the energy gap to be able to get to the next from white light

The complimentary colour to the frequency absorbed is the colour of the complex

34
Q

What are the advantages and disadvantages of hydrogen fuel cells over fossil fuels?

A

Advantages
Only water formed/ non polluting

Greater efficiency

Disadvantages
Difficult to store h2
Difficult to manufacture initially
Limited life cycle of h2 adsorber/absorber

35
Q

What is standard electrode potential?

A

The potential difference of an electrochemical cell comprising a half cell combined with a standard electrode at standard conditions
1atm, 1 moldm-3, 298K

36
Q

Give one use of chromium metal and state the property that makes it suitable

A

Stainless steel

Corrosion resistance

37
Q

What are 2 examples of small ligands?

A

Water and ammonia

38
Q

What is an example of large ligand?

A

Chlorine ions

39
Q

What is a Brønsted-Lowry base?

A

Accepts H+ /protons

40
Q

What do dilute ammonia and sodium hydroxide solution act as when reacting with transition metals?

A

Brønsted-Lowry bases

41
Q

What happens when excess ammonia solution is added to copper metal ions (not in iron)?

A

Ligand substitution

4ammonia Ligands and 2 water

42
Q

What happens when dilute ammonia or sodium hydroxide is added to fe or Cu?

A

Have 2 OH Ligands and 4water

43
Q

Discuss two advantages and two disadvantages of using hydrogen fuels cells for energy
rather than using fossil fuels.

A

advantages:
only H2O formed/ non-polluting
greater efficiency

disadvantages:
H2 difficult to store
H2 difficult to manufactured initially /
limited life cycle of H2 adsorber/absorber

44
Q

Define the term standard electrode potential.

A

potential difference (of electrochemical cell)
comprising of a half cell combined with a standard
hydrogen electrode 1
1 atm, 1 mol.dm–3
, 298K

45
Q

what does it mean is a substance has a really positive standard electrode potential?

A

it is a strong oxidising agent

46
Q

in an electrochemical cell in which direction do electrons flow?

A

towards the half cells with the more positive standard electrode potential

47
Q

why does a more positive electrode potential make a better oxidising agent?

A

they have a greater tendancy to gain electrons

48
Q

why might a redox reaction in an electrochemical cell not occur?

A

electrode potenrial may be too small, rate is too slow, not enough activation energy, not standard conditions

49
Q

how can you use colorimetry to find the concentration a substance and the rate

A

choose filter with complementary colour to the substance you are trying to measure the concentration of

make up stand solutions of coloured solutions

zero the colorimeter with water

measure absorbance of each standard solution

plot calibration curve (absorbance against concentration)

measure the absorbance of the unknown sample at certain times throughout the reaction

use graph to read off each concentration for each absorbance measured

plot concentration against time and find rate

50
Q

why does iron corrode in the centre of a water droplet not at the edge?

A

the oxygen concentration is at its lowest here

51
Q

what can electrochemical cells be used for?

A

to measure concentration of ions in a solution

Chemistry OCR B Alevel (14 decks)

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