Chapter 24 - Transition Elements Flashcards
D-block element, The formation and shapes of complex ions, Stereoisomerism in complex ions, Ligand substitution and precipitation, Redox and qualitative analysis.
What are the two special cases in the d-block in terms of electron configuration?
1) Chromium: 3d5 4s1 instead of 3d4 4s2. Half filled subshell
2) Copper: 3d10 4s1 instead of 3d9 4s2. Full subshell
Why do these special cases exist in the d block electron configurations?
A half filled and a fully filled d sub shell gives greater stability to these atoms.
What are transition elements?
D-block elements that form at least one ion with a partially filled d-orbital.
Which d-block elements are excluded from being transition elements?
Scandium and zinc. scandium forms a sc 3+ ion and zinc forms a Zn 2+ ion.
the zinc is empty and scandium is scant.
What are the properties of the transition elements?
1) transition elements form compounds with different oxidation states.
2) Form coloured compounds
3) Elements and compounds can act as catalysts
what are the colours of the various ions of iron?
iron 2+ - pale green
iron 3+ - yellow
What colours are the various ions of Chromium (Cr) ? what are the colours?
chromium/cr 3+ is green
chromium/cr 6+ is yellow / orange
What colours are the various ions of Copper?
Cu 2+ is blue
Cu + and Cu 3+ is colourless
table of common oxidation states and their colours?
What colour is potassium dichromate(VI)?
K2Cr2O7 is Orange
What colour is cobalt(II) chloride?
cobalt(II) chloride is Pink-purple
What colour is nickel(II) sulfate (NiSO₄) ?
NiSO₄ is Green
What colour is hydrated copper(II) sulfate?
Blue
What is the catalyst used in the Haber process?
an iron catalyst is used in the haber proccess.
N2 (g) + 3H2 (g) = 2NH3 (g)
What is the catalyst used in the production of sulfur trioxide for the manufacture of sulfuric acid?
Vanadium(V) oxide
V2O5
2SO2 (g) + O2 (g) = 2SO3
What is the catalyst used in hydrogenation?
Nickel
What is the catalyst used in the reaction of zinc metal with acids?
Cu 2+ ions are used as a catalyst in the reaction of zinc metal with acids : Zn (s) + H2SO4 = ZnSO4 (aq) + H2 (g)
What is the catalyst used in catalytic decomposition of hydrogen peroxide?
Manganese(IV) oxide
MnO2
2H202 (aq) = 2H2O (l) + O2
Define what a complex ion is
A complex ion is formed when ligands bond to a central transition metal ion.
Define coordination number
The number of coordinate bonds attached to the central metal ion.
Define what a ligand is
A molecule or ion that can donates a pair of electrons to the central transition metal ion to form a coordinate bond or dative covalent bond.
What is meant by a monodentate ligand?
A ligand that is able to donate one (hence mono) pair of electrons to a central metal ion.
Give 5 examples of common monodentate ligands and their charges
what is a bidentate ligand?
A bidentate (bi = two) ligand donates two pairs of electrons to the central metal ion
how is a complex ion shown?
Define denticity
The number of separate sites in a molecule or ion that can donate an electron pair to a transition metal ion.
What shape is created from a complex ion having a coordination number of 6?
an Octahedral shape is formed when it has a coordination number of six.
what is an octahedral shape?
an octahedral shape has:
1) the ligands arranged at the corners of the octahedron
2) bond angles of 90 degrees around the central metal ion
What shapes can be created from a complex ion having a coordination number of 4?
when there is a coordination number if 4 the shape is:
Tetrahedral
OR
Square planar
When is a square planar shape formed in a complex ion?
When the transition metal in the complex ion has eight d-electrons in the highest energy d-sub-shell. e.g platinum (II) and palladium (II)
What is stereoisomerism?
Same structural formula but a different arrangement of the atoms in space.
What are the two types of stereoisomerism?
Cis-trans isomerism
Optical isomerism
when does cis-trans isomerism exist in monodente square planar complexes? what is the general formula?
cis and trans isomers exist in square planar complexes with:
1) two molecules/ions of one monodentate ligand, X
2) two molecules/ions of another monodentate ligand Y
the general formula is [MX2Y2]n (n=charge)
When can complex ions show cis-trans isomerism?
cis-trans isomers exist in square planar and octahedral complex ions.
how does optical isomerism occur with both bidentate and monodentate ligands?
cis isomers of octohedral complexes have optical isomers if they have:
1) two molecules/ions of a bidentate ligand
2) two molecules/ions of a monodentate ligand
how does cis-trans isomerism occur in octahedrals with monodentate ligands?
cis and trans isomers exist in in octahedral complxes with:
1) four molecules or ions of one monodentate ligand X
2) two molecules/ions of another mondentate ligand Y
the general formula is [MX4Y2]n (n=charge)
When can complex ions show both types of stereoisomerism?
Six coordinate complex ions containing monodentate and bidentate ligands.
What is optical isomerism?
Non-superimposable mirror images of each other.
Called enantiomers
Define ligand substitution
Ligand substitution is a reversible reaction of a complex ion where One ligand in a complex ion is replaced by another ligand.
Describe ligand substitution of aqueous copper(II) ions with ammonia, NH3
Four H2O molecules are replaced by ammonia (NH3) ligands, the solution turns from pale blue to dark blue.
[Cu(H2O)6] 2+ + 4NH3 = [Cu(NH3)4(H2O)2]2+ + 4H2O (l)
pale blue to dark blue
Describe the ligand substitution of aqueous ammonia, NH3 with [Cr(H2O)6]3+ ?
six H2O molecules are replaced with six NH3 ligands to form [Cr(NH3)6}3+
the colour changes from violet to purple
[Cr(H2O)6]3+ + 6NH3 = [Cr(NH3)6}3+ + 6H2O
violet solution purple solution
Describe ligand substitution of aqueous copper(II) ions with chloride ions
six H2O ligands are replaced by 4 chloride ions Cl- ligands. The solution starts out pale blue and moves to yellow on completion.
[Cu(H2O)6]2+ + 4Cl- = [CuCl4]2- + 6H2O
Why does the solution of aqueous copper (II) ions reacting with chloride ions turn green as the reaction proceeds?
The yellow and blue solutions mixing gives a green colour.
Why does the shape of the aqueous copper (II) ion change from octahedral to tetrahedral when it reacts with chloride ions?
Chloride ligands are larger in size than water ligands so fewer of them can fit around the Cu2+ ion.
What is formed when chromium(III) potassium sulphate is dissolved in water? what’s the formula and colour?
The complex ion [Cr(H2O)6]3+ is formed.
A pale purple solution.
What is formed instead when only chromium(III) sulphate is dissolved in water?
The complex ion [Cr(H2O)5SO4]+ is formed.
A green solution.
Describe the reaction between [Cr(H2O)6]3+ and an excess of aqueous ammonia
A grey green precipitate of Cr(OH)3 is formed initially.
Cr(OH)3 dissolves in excess ammonia to form the complex ion [Cr(NH3)6]3+.
A purple solution.
why is carbon monoxide bonding to haemoglobin so bad?
carbon monoxide can bond to haemoglobin but the process is irreversible as the bond is so strong. can lead to death.
How does ligand substitution help with gas exchange in blood?
haemoglobin in red blood cells contain four protein chains
1) Each protein chain has a planar haem molecule within its structure
2) The Fe 2+ metal ion in haem bonds to a protien chain and water
3) the water can exchange for oxygen gas or CO2
Hb + O2 = HbO2
What is a precipitation reaction?
a precipitation reaction is when Two aqueous solutions contain ions react together to form an insoluble ionic solid. (the precipitate)
Describe the precipitation reaction of Fe2+ with OH and what is the equation?
Fe2+ + 2OH (OH- ions) = Fe(OH)2 (s)
pale green solution to green precipitate
Describe the precipitation reaction of Fe3+ with OH and what is the equation?
Fe3+ + 3OH- = Fe(OH)3 (s)
pale yellow to orange-brown precipitate
Describe the precipitation reaction of Mn2+ with OH and what is the equation?
Mn2+ + 2OH- = Mn (OH)2 (s)
pale pink solution to light brown precipitate
Describe the precipitation reaction of Cr3+ with OH and what is the equation?
Cr3+ (aq) + 3OH- (aq) = Cr(OH)3 (s)
violet solution to green precipitate
Describe the precipitation reaction of Cu2+ with NaOH and what is the equation?
Cu2+(aq)+2NaOH(aq)→ Cu(OH)2(s)+2Na+(aq)
pale Blue solution blue precipitate of copper(II) hydroxide.
Insoluble in excess NaOH.
How do Cr3+ react with an excess of aqueous NaOH?
the hydroxide of Cr 3+ does dissolve in excess NaOH
Cr3+ =(NaOH (aq))= Cr(OH)3 (s) =excess NaOH=[Cr (OH)6] 3-
Violet solution green precipitate dark green solution
How do Cu2+, Fe2+, Fe3+ and Mn2+ react with an excess of aqueous ammonia?
The hydroxides of Fe 2+,Fe 3+ and Mn2+ do not dissolve in excess NaOH
What is the catalyst used in the reaction of zinc metal with acids?
Cu 2+ ions are used as a catalyst in the reaction of zinc metal with acids : Zn (s) + H2SO4 = ZnSO4 (aq) + H2 (g)
how does Fe2+, Fe3+ and Mn 2+ react with excess NH3?
the hydroxides of Fe2+, Fe3+ and Mn2+ do not dissolve in excess NH3
how do the hydroxides of Cu2+ and Cr2+ react with excess NH3?
the hydroxides of Cu2+ and Cr2+ do dissolve in excess NH3 (aq)
Cr 3+ (aq) = Cr(OH)3 (s) = [Cr(NH3)6]3+
violet solution green precipitate purple solution
Cu2+ = Cu(OH)2 (s) = [Cu(NH3)4(H2O)2]2+
pale blue solution blue preciptate dark blue solution
what happens in the reavttion between Fe2+ ions and acidified magnate (VII) ions MnO4 - ?
MnO4 - (aq) + 8H+ (aq) + 5Fe2+ (aq) = Mn2+ (aq) + 5 Fe3+ (aq) + 4H2O (l)
purple to colourless
fe 2+ is oxidised to Fe3+
Mn is reduced from +7 in Mn04- to +2 in Mn2+
what happens when Fe 3+ is added to iodine ions?
Fe3+ ions are reduced to Fe2+ ions by iodide ions I- (aq)
2Fe3+ + 2 I- (aq) = 2Fe2+ (aq) + I2 (aq)
yellow ornge pale green brown
Fe3+ is reduced to Fe2+
I- is oxidised to I2
what happens when acidified dichromate (VI) ions (Cr2O7)2- are added to zinc metal?
Cr2O7 2- + 14H+ + 3Zn = 2Cr 3+ + 7 H2O (l) + 3Zn 2+
orange green
cr is reduced from +6 to 3+
zn is oxidsed from 0 to +2
chromium(III) Cr3+ ions + hot alkaline hydrogen peroxide , H2O2?
2Cr3+ + 3H2O2 + 10 OH- = 2CrO4 2- (aq) + 8H2O
YELLOW SOLUTION
(Cu 2+ ) + (iodide ions) I- = ?
2Cu2+ + 4I- = 2 CuI (s) + I2 (aq)
pale blue solution to a brown solution + white precipitate
Cu2O + hot dilute sulferic acid = ?
Cu2O (s) + H2SO4 = Cu (s) + CuSO4 (aq) + H2O
red-brown solid brown solid and a blue solution
this is a disproportionation reaction :) as cu is both oxidised and reduced
what are the tests for anions?
you got this
don’t give up :)
max is a sexy cunt
;)
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