| Date | May 2017 | Marks available | 2 | Reference code | 17M.2.sl.TZ1.2 |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Describe | Question number | 2 | Adapted from | N/A |
Question
Titanium is a transition metal.
TiCl4 reacts with water and the resulting titanium(IV) oxide can be used as a smoke screen.
Describe the bonding in metals.
Titanium exists as several isotopes. The mass spectrum of a sample of titanium gave the following data:
Calculate the relative atomic mass of titanium to two decimal places.
State the number of protons, neutrons and electrons in the \({}_{22}^{48}{\text{Ti}}\) atom.
State the full electron configuration of the \({}_{22}^{48}{\text{Ti}}\)2+ ion.
Explain why an aluminium-titanium alloy is harder than pure aluminium.
State the type of bonding in potassium chloride which melts at 1043 K.
A chloride of titanium, TiCl4, melts at 248 K. Suggest why the melting point is so much lower than that of KCl.
Formulate an equation for this reaction.
Suggest one disadvantage of using this smoke in an enclosed space.
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]
\(\frac{{(46 \times 7.98) + (47 \times 7.32) + (48 \times 73.99) + (49 \times 5.46) + (50 \times 5.25)}}{{100}}\)
= 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]
1s22s22p63s23p63d2
[1 mark]
titanium atoms/ions distort the regular arrangement of atoms/ions
OR
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]
ionic
OR
«electrostatic» attraction between oppositely charged ions
[1 mark]
«simple» molecular structure
OR
weak«er» intermolecular bonds
OR
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]
TiCl4(l) + 2H2O(l) → TiO2(s) + 4HCl(aq)
correct products
correct balancing
Accept ionic equation.
Award M2 if products are HCl and a compound of Ti and O.
[2 marks]
HCl causes breathing/respiratory problems
OR
HCl is an irritant
OR
HCl is toxic
OR
HCl has acidic vapour
OR
HCl is corrosive
Accept “TiO2 causes breathing problems/is an irritant”.
Accept “harmful” for both HCl and TiO2.
Accept “smoke is asphyxiant”.
[1 mark]
