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Date November 2018 Marks available 2 Reference code 18N.2.sl.TZ0.3
Level SL Paper 2 Time zone TZ0
Command term Deduce Question number 3 Adapted from N/A

Question

Bromine can form the bromate(V) ion, BrO3.

State the electron configuration of a bromine atom.

[1]
a.i.

Sketch the orbital diagram of the valence shell of a bromine atom (ground state) on the energy axis provided. Use boxes to represent orbitals and arrows to represent electrons.

[1]
a.ii.

Draw the Lewis (electron dot) structure for BrO3 that obeys the octet rule.

[1]
b.

Predict, using the VSEPR theory, the geometry of the BrO3 ion and the O−Br−O bond angles.

[3]
c.

Bromate(V) ions act as oxidizing agents in acidic conditions to form bromide ions.

Deduce the half-equation for this reduction reaction.

[2]
d.i.

Bromate(V) ions oxidize iron(II) ions, Fe2+, to iron(III) ions, Fe3+.

Deduce the equation for this redox reaction.

[1]
d.ii.

Markscheme

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

OR

[Ar] 4s2 3d10 4p5

 

Accept 3d before 4s.

a.i.

Accept double-headed arrows.

a.ii.

Accept dots, crosses or lines to represent electron pairs.

b.

Geometry:
trigonal/pyramidal ✔

Reason:
three bonds AND one lone pair
OR
four electron domains ✔

O−Br−O angle:
107° ✔

 

Accept “charge centres” for “electron domains”.

Accept answers in the range 104–109°.

c.

BrO3 (aq) + 6e + 6H+ (aq) → Br (aq) + 3H2O (l)

correct reactants and products ✔

balanced equation ✔

 

Accept reversible arrows.

d.i.

BrO3 (aq) + 6Fe2+ (aq) + 6H+ (aq) → Br (aq) + 3H2O (l) + 6Fe3+ (aq) ✔

 

d.ii.

Examiners report

[N/A]
a.i.
[N/A]
a.ii.
[N/A]
b.
[N/A]
c.
[N/A]
d.i.
[N/A]
d.ii.

Syllabus sections

Core » Topic 9: Redox processes » 9.1 Oxidation and reduction
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