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Chemistry > Transition elements Module 5 > Flashcards

Transition elements Module 5 Flashcards

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1
Q

Where are the transition elements found?

A

In the d block

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2
Q

Definition of a transistion element?

A

A d block element, that can form at least one stable ion with an incomplete d sub shell

So scandium and Zinc aren’t transition elements

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3
Q

Which transition elements are exceptions to the electron configuration filling up rules?

A

Chromium- prefers to have one electron in each orbital of the 3d subshell and just one in the 4s subshell, makes it more stable

Copper- prefers to have a full 3d subshell, and only one electron in the 4s subshell

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4
Q

When transition elements form ions, what shell are the electrons lost from first?

A

4s

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5
Q

Why scandium and Zinc aren’t transition elements?

A

Zn2+ only ion, which has a full d subshell

Sc3+ only ion, doesn’t have a d subshell

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6
Q

What is special about oxidation numbers in transition elements?

A

They can exist in variable oxidation states

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7
Q

Why are transistion elements good catalysts?

A

They can change oxidation states by losing or gaining electrons, within their d orbitals, so can transfer electrons to speed up reactions

Good at adsorbing substances onto their surfaces to lower the activation energy of reactions

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8
Q

3 examples of transition elements acting as catalysts?

A

CuSO4 catalyses the reaction of zinc with acids

MnO4 catalyses the decomposition of hydrogen peroxide

Iron is the catalyst in the haber process to produce ammonia

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9
Q

Pros and cons of catalysts?

A

Good for industry and the environment, as they allow reactions to happen faster, and at lower temperatures and pressures reducing energy usage

Can pose health risks as many of the metals and their compounds are toxic

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10
Q

Formula for when a transition element, is in aqueous solution?

A

{M(H2O)6)n+

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11
Q

What happens when you mix Copper(II) with NH3 (including equations)?

A

Cu2(+) + 2OH- = Cu(OH)2 goes from pale blue solution to a pale blue precipitate
OH is there as NH3 is a weak alkali

Then in excess NH3,Cu(OH)2 dissolves to form {Cu(NH3)4(H2O)2}2+ which is a dark blue colour

So the reaction is 4NH3 + {Cu(H20)6}2+ = (reversible) {Cu(NH3)4(H20)2}(2+) + 4H2O

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12
Q

What happens when you mix Iron(II) with NH3 (including equations)?

A

Fe(2+) + 2OH- = Fe(OH)2 pale green solution to a green precipitate, OH there as NH3 is a weak alkali

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13
Q

What happens when you mix Iron(III) with NH3 (including equations)?

A

Fe3+ + 3OH- = Fe(OH)3 goes from yellow solution to an orange precipitate, OH there as NH3 is a weak acid

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14
Q

What happens when you mix Manganese (II) with NH3 (including equations)?

A

Mn(2+) + 2OH- = Mn(OH)2 goes from pale pink solution to a light brown precipitate

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15
Q

What happens when you mix Chromium (III) with NH3 (including equations)?

A

Cr(3+) + 3OH- = Cr(OH)3 goes from a purple solution to a grey-green precipitate

Then in excess NH3, Cr(OH)3 dissolves to form {Cr(NH3)6}(3 +)which is a purple solution

So the equation is {Cr(H2O)6} + 6NH3 =(reversible) {Cr(NH3)6}(3+) + 6H20

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16
Q

What’s a complex ion?

A

A metal ion surrounded by coordinately (dative bond, both electrons are from the same atom) bonded ligands

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17
Q

What’s a ligand?

A

An atom, ion or molecule, that donates a pair of electrons to a central metal atom or ion

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18
Q

What’s the coordination number?

A

The number of coordinate bonds that are formed with the central metal atom (will either be 4 or 6)

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19
Q

What shape does 6 coordinate bonds form?

A

An octahedral shape, 90 degree bond angle

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20
Q

What shape does 4 coordinate bonds form?

A

Tetrahedral shape, 109.5 degree bond angle, or a square planar shape 90 degree bond angle

21
Q

What must all ligands have?

A

A lone pair of electrons to be able to form the coordinate bond

1 lone pair = monodentate
2 lone pairs = bidentate, so can form 2 coordinate bonds with central atom

22
Q

When can optical ismomerism occur in complex ions?

A

Occurs when an ion can exist in 2 non-superimposable mirror images (don’t match each other when put on top of each other)

So occurs when in octahedral complexes, when 3 biodentate ligands are attached to the central ion

23
Q

How can cis-trans isomerism occur in complex ions?

A

When there’s only 2 different groups involved

The Cis isomers have the same groups on the same side (so are close together as they can be)

Trans have the same groups on opposite side

24
Q

What is Cis platin?

A

A complex of platinum(II), with 2 chloride ions and 2 ammonia molecules in a square planar shape

25
Q

How does Cis-Platin act as an anti cancer drug?

A

The 2 chloride ligands are very easy to displace. So the cis-platin displaces them, and bonds to 2 Nitrogen atoms on the DNA molecule, inside the cancerous cell instead

This block on it’s DNA prevents the cancerous cell from reproducing by division, causing the cell to die as unable to repair the damage

26
Q

Why does Cis-platin need to be CIs and not Trans?

A

Needs the 2 chloride ions to be next to each other, in order to bind and work correctly

27
Q

Downside of Cis-Platin as a cancer treatment?

A

Prevents normal cells from reproducing, including blood, so represses the immune system, increasing risk of infection
Can also damage the kidneys

28
Q

In ligand subsitution what happens if the ligands are of similar size, eg H20, NH3 or CN-?

A

The ligands directly swap places, and the coordination number stays the same

(sometimes may be partial)

29
Q

In ligand subsitution what happens if the ligands are of different sizes, eg H2O and Cl-?

A

There’s a change of coordination number and shape

30
Q

How do you write a ligand substiution reaction?

A

Complex ion and reactant ligand on one side
Reversible reaction sign
New complex ion (coordination number, shape and charge may have changed) and the displaced ligand

31
Q

Describe the Ligand substiution in haemoglobin?

A

Haemoglobin contains Fe2+ ions, which form 6 coordinate bonds, 4 of the lone pairs come from Nitrogen atoms, within a circular part of the molecule called haem, the fifth lone pair comes from a nitrogen atom binded to a protein (globin) The last one is a water ligand which attaches to the Iron

In the lungs there is high oxygen concentration, so the water ligand is substituted for an Oxygen molecule, forming oxyhaemoglbobin, this is then transported to respiring tissues where the oxygen is now dropped off and O2 concentration is low, so H2O binds back on

Can explain this reffering to le Chateillers principles and the reversible equation

32
Q

What happens if CO is inhaled?

A

Water ligand is swapped for CO, forming a carboxyhaemoglobin, it’s a strong ligand so won’t readily exchange back with oxygen or water lingands, meaning haemoglobin can’t transport oxygen anymore

33
Q

How do transition elements change oxidation number?

A

By gaining or losing electrons during a redox reaction

34
Q

Describe the interconversion between Fe 2+ ions and Fe3+ ions?

A

Fe(2+) ions (pale green) are oxidised to Fe(3+) (yellow), by acidified potassium manganate solution

Fe(3+) ions (yellow) are reduced to Fe(2+) ions (pale green) by Iodide ions

35
Q

Interconversion between Cr(3+) and Cr2O7(2-)?

A

Cr(3+) ion in (Cr(OH)6)3- (dark green) is oxidised to the yellow CrO4(2-) by warming with hydrogen peroxide solution in alkaline conditions

Then dilute sulfuric acid is added to CrO4(2-) to produce the orange Cr2O7(2-)

Cr2O7(2-) (orange) is reduced to Cr3+ (green) by acidified zinc

36
Q

Interconversion between Cu2+ and Cu+?

A

Cu(2+) (pale blue) is reduced to the off-white precipitate Copper iodide by iodide ions

Cu(+) spontaneously disproportionates into to produce Cu and Cu(2+)

37
Q

What colour precipitate is formed, when NaOH is reacted with the transistion Ion Cu(2+)?

A

blue

38
Q

What colour precipitate is formed, when NaOH is reacted with the transistion Ion Fe(2+)?

A

green

39
Q

What colour precipitate is formed, when NaOH is reacted with the transistion Ion Fe(3+)?

A

Orange

40
Q

What colour precipitate is formed, when NaOH is reacted with the transistion Ion Mn(2+)?

A

Light brown

41
Q

What colour precipitate is formed, when NaOH is reacted with the transistion Ion Cr(3+)?

A

Grey/green

42
Q

How do you test for a carbonate ligand?

A

Add Nitric acid to the test compound, and bubble any gas given off through limewater

Limewater will go cloudy if present, as CO2 produced

43
Q

How do you test for a chloride ligand?

A

Add silver nitrate to the compound

White precipitate formed if present

44
Q

How do you test for a bromide ligand?

A

Add silver nitrate to the compound

Cream precipitate forms if present

45
Q

How do you test for an Iodide ligand?

A

Add silver nitrate to the compound

Yellow precipitate forms if present

46
Q

How do you test for Sulphate ligand?

A

Add Barium Nitrate or Barium Chloride, white precipitate will form if present

47
Q

How do you test for an ammonium ligand?

A

Add cold NaOH to the test compound and warm, hold damp, red litmus paper over the solution

Red litmus paper will turn blue in presence of ammonia

48
Q

How do you get [Cr(OH)6]?

A

React Cr(OH)3 with NaOH

49
Q

How do you get {Cu(Cl)4}2-?

A

{Cu(H2O)6}(2+) + 4Cl- =(reversible) {Cu(Cl)4}(2-) + 6H2O

Chemistry (26 decks)

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