transition elements Flashcards
What is the oxidation number of Cr in the complex ion [CrOCl5]2–
+5
Write the equation for a reaction catalysed by a named transition element, compound or ion.
N2 + 3H2 ⇌ 2NH3 (allow →) AND Fe/iron oxide
2SO2 + O2 ⇌ 2SO3 (allow →) AND V2O5/Pt
2CO + 2NO → 2CO2 + N2 AND Pt/Pd/Rh/Au
Equation for any alkene + H2 → alkane AND Ni/Pt/Pd
C6H6 + Cl2 → C6H5Cl + HCl AND Fe/FeCl3/Fe3+
C6H6 + Br2 → C6H5Br + HBr AND Fe/FeBr3/Fe3+
2H2O2 → 2H2O + O2 AND MnO2
State what is meant by a bidentate ligand.
Donates two electron pairs (to a metal ion)
AND
forms two coordinate bonds (to a metal ion)
Describe the reactions of EITHER aqueous copper(II) ions:
•aqueous sodium hydroxide
•excess aqueous ammonia
•hydrochloric acid.
REACTIONS OF AQUEOUS Cu2+ ----------------------------------------------------------------------------- REACTION OF Cu2+ with NaOH(aq) Correct balanced equation Cu2+(aq) + 2OH–(aq) ⎯→ Cu(OH)2(s) state symbols not required Observation blue precipitate/solid REACTION OF Cu2+ WITH excess NH3(aq) Correct balanced equation [Cu(H2O)6]2+ + 4NH3 ⎯→ [Cu(NH3)4(H2O)2]2+ + 4H2O Observation deep/dark blue (solution) REACTION OF Cu2+ WITH HCl(aq) Correct balanced equation [Cu(H2O)6]2+ + 4Cl– ⎯→ [CuCl4]2– + 6H2O Observation yellow (solution)
Explain why two of the Period 4 d-block elements (Sc–Zn) are not also transition elements.
In your answer you should link full electron configurations to your explanations.
(Transition element) has an ion with an incomplete/partiallyfilled
d sub-shell/d-orbital
Scandium/Sc and zinc/Zn are not transition elements
Electron configurations of ions
Sc3+ AND 1s2
2s2
2p6
3s2
3p6
Zn2+ AND 1s2
2s2
2p6
3s2
3p6
3d10
Sc3+ AND d sub-shell empty / d orbital(s) empty
Note: Sc3+ must be the ONLY scandium ion shown for this
mark
Zn2+ AND d sub-shell full /ALL d-orbitals full
Note: Zn2+ must be the ONLY zinc ion shown for this mark
Explain how ligand substitution reactions allow haemoglobin to transport oxygen in blood.
O2/oxygen bonds to Fe2+/Fe(II)
Fe2+/Fe(II) essential for 1st marking point
(When required,) O2 substituted OR O2 released
Fe2+ not required for 2nd marking point (e.g. IGNORE Fe)
n the presence of carbon monoxide, less oxygen is transported in the blood.Suggest why, in terms of bond strength and stability constants.
Stability constant/Kstab value with CO is greater (than with
complex in O2)
(Coordinate) bond with CO is stronger (than O2)
OR CO binds more strongly
Define the term transition element.Show that iron fits this definition by use of full electron configurations of iron as the element and in its common oxidation states.
(A transition element) has (at least) one ion with a
partially filled d sub-shell/ d orbital
Fe AND 1s22s22p63s23p63d64s2
Fe(II) / Fe2+ AND 1s22s22p63s23p63d6
Fe(III) / Fe3+ AND 1s22s22p63s23p63d5
Describe one precipitation reaction and one ligand substitution reaction of copper in the +2 oxidation state.Your answer should include reagents, relevant observations and balanced equations.
PRECIPITATION Reagent NaOH(aq) OR KOH(aq) States not required Transition metal product AND observation Cu(OH)2 AND blue precipitate/solid Correct balanced equation Cu2+(aq) + 2OH–(aq) Cu(OH)2(s) state symbols not required LIGAND SUBSTITUTION – 2 likely Reagent NH3(aq)/ammonia State not required Transition metal product AND observation [Cu(NH3)4(H2O)2]2+ AND deeper/darker blue (solution) Correct balanced equation [Cu(H2O)6]2+ + 4NH3 [Cu(NH3)4(H2O)2]2+ + 4H2O OR ------------------------------------------------------- Reagent Concentrated HCl OR (dilute) HCl(aq) OR NaCl(aq) State not required Transition metal product AND observation CuCl ]2– [ 4 AND yellow (solution) 2 6 4 2 Correct balanced equation Cu(H O) ]2+ + 4Cl– [CuCl ]2– [ + 6H O
State one property of cobalt(II) and cobalt(III), other than their ability to form complex ions, which is typical of ions of a transition element.
catalyst OR coloured
State the meaning of the term ligand.
Donates an electron/lone pair to a metal ion
OR forms a coordinate bond to a metal ion
Aqueous cobalt(II) sulfate, CoSO4(aq), reacts with aqueous sodium hydroxide. transition element species formed: .................................................................................... type of reaction: ............................................................................................................
Co(OH)2
precipitation
Aqueous cobalt(II) sulfate, CoSO4(aq), reacts with concentrated hydrochloric acid. transition element species formed: .................................................................................... type of reaction: ....................................................................................
CoCl42–
ligand substitution
Using the information about nickel above, explain the meaning of the terms d-block element, transition element, ligand and complex ion.Include electron structures and diagrams in your answer.
Ni 1s22s22p63s23p63d84s2
d block: (Ni:) ‘d’ is highest energy sub-shell/orbital
Ni2+: 1s22s22p63s23p63d8
Transition element: has an ion with an
incomplete/partially-filled d sub-shell/orbital
A ligand donates an electron pair to Ni2+ OR metal ion
OR metal
A complex ion is an ion bonded to
ligand(s)/surrounded by ligands
Coordinate bond/dative covalent mentioned at least
once in the right context
Explain how ligand substitutions allow haemoglobin to transport oxygen in the blood.
O2/oxygen bonds to Fe2+/Fe(II)/Fe
When required, O2 substituted OR O2 released
