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Date	May 2017	Marks available	1	Reference code	17M.2.hl.TZ1.2
Level	HL	Paper	2	Time zone	TZ1
Command term	Suggest	Question number	2	Adapted from	N/A

Question

Titanium and vanadium are consecutive elements in the first transition metal series.

${\text{TiC}}{{\text{l}}_{\text{4}}}$ reacts with water and the resulting titanium(IV) oxide can be used as a smoke screen.

Describe the bonding in metals.

[2]

Titanium exists as several isotopes. The mass spectrum of a sample of titanium gave the following data:

M17/4/CHEMI/HP2/ENG/TZ1/02.b

Calculate the relative atomic mass of titanium to two decimal places.

[2]

State the number of protons, neutrons and electrons in the $_{{\text{22}}}^{{\text{48}}}{\text{Ti}}$ atom.

M17/4/CHEMI/HP2/ENG/TZ1/02.c

[1]

State the full electron configuration of the $_{{\text{22}}}^{{\text{48}}}{\text{T}}{{\text{i}}^{2 + }}$ ion.

[1]

d.i.

Suggest why the melting point of vanadium is higher than that of titanium.

[1]

d.ii.

Sketch a graph of the first six successive ionization energies of vanadium on the axes provided.

M17/4/CHEMI/HP2/ENG/TZ1/02.d.iii

[1]

d.iii.

Explain why an aluminium-titanium alloy is harder than pure aluminium.

[2]

d.iv.

Describe, in terms of the electrons involved, how the bond between a ligand and a central metal ion is formed.

[1]

Outline why transition metals form coloured compounds.

[4]

State the type of bonding in potassium chloride which melts at 1043 K.

[1]

g.i.

A chloride of titanium, ${\text{TiC}}{{\text{l}}_{\text{4}}}$ , melts at 248 K. Suggest why the melting point is so much lower than that of KCl.

[1]

g.ii.

Formulate an equation for this reaction.

[2]

h.i.

Suggest one disadvantage of using this smoke in an enclosed space.

[1]

h.ii.

Markscheme

electrostatic attraction

between «a lattice of» metal/positive ions/cations AND «a sea of» delocalized electrons

Accept “mobile electrons”.

Do not accept “metal atoms/nuclei”.

[2 marks]

$\frac{{(46 \times 7.98){\text{ + }}(47 \times 7.32){\text{ + }}(48 \times 73.99){\text{ + }}(49 \times 5.46){\text{ + }}(50 \times 5.25)}}{{100}} = 47.93$

Answer must have two decimal places with a value from 47.90 to 48.00.

Award [2] for correct final answer.

Award [0] for 47.87 (data booklet value).

[2 marks]

Protons: 22 AND Neutrons: 26 AND Electrons: 22

[1 mark]

${\text{1}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{s}}^{\text{2}}}{\text{3}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{d}}^{\text{2}}}$

[1 mark]

d.i.

vanadium has smaller ionic radius «leading to stronger metallic bonding»

Accept vanadium has «one» more valence electron«s» «leading to stronger metallic bonding».

Accept “atomic” for “ionic”.

[1 mark]

d.ii.

regular increase for first five AND sharp increase to the 6th

A log graph is acceptable.

Accept log plot on given axes (without amendment of y-axis).

Award mark if gradient of 5 to 6 is greater than “best fit line” of 1 to 5.

[1 mark]

d.iii.

titanium atoms/ions distort the regular arrangement of atoms/ions

titanium atoms/ions are a different size to aluminium «atoms/ions»

prevent layers sliding over each other

Accept diagram showing different sizes of atoms/ions.

[2 marks]

d.iv.

pair of electrons provided by the ligand

Do not accept “dative” or “coordinate bonding” alone.

[1 mark]

partially filled d-orbitals

«ligands cause» d-orbitals «to» split

light is absorbed as electrons transit to a higher energy level «in d–d transitions»
OR
light is absorbed as electrons are promoted

energy gap corresponds to light in the visible region of the spectrum

colour observed is the complementary colour

[4 marks]

ionic

«electrostatic» attraction between oppositely charged ions

[1 mark]

g.i.

«simple» molecular structure

weak«er» intermolecular bonds

weak«er» bonds between molecules

Accept specific examples of weak bonds such as London/dispersion and van der Waals.

Do not accept “covalent”.

[1 mark]

g.ii.

${\text{TiC}}{{\text{l}}_{\text{4}}}{\text{(l)}} + {\text{2}}{{\text{H}}_{\text{2}}}{\text{O(l)}} \to {\text{Ti}}{{\text{O}}_{\text{2}}}{\text{(s)}} + {\text{4HCl(aq)}}$ correct products
correct balancing