DP Chemistry (last assessment 2024)

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Question 18M.3.sl.TZ2.3c.iii

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Date May 2018 Marks available [Maximum mark: 2] Reference code 18M.3.sl.TZ2.3c.iii
Level sl Paper 3 Time zone TZ2
Command term Outline Question number c.iii Adapted from N/A
c.iii.
[Maximum mark: 2]
18M.3.sl.TZ2.3c.iii

Inductively Coupled Plasma (ICP) used with Mass Spectrometry (MS) or Optical Emission Spectrometry (OES) can be used to identify and quantify elements in a sample.

The following graphs represent data collected by ICP-OES on trace amounts of vanadium in oil.

Graph 1: Calibration graph and signal for 10 μg kg−1 of vanadium in oil

Graph 2: Calibration of vanadium in μg kg−1

[Source: © Agilent Technologies, Inc.1998. Reproduced with Permission, Courtesy of Agilent Technologies, Inc.]

(c.iii)

Vanadium(V) oxide is used as the catalyst in the conversion of sulfur dioxide to sulfur trioxide.

SO2(g) + V2O5(s) → SO3(g) + 2VO2(s)

1 2 O2(g) + 2VO2(s) → V2O5(s)

Outline how vanadium(V) oxide acts as a catalyst.

[2]

Markscheme

vanadium reduced in first reaction AND oxidized in second reaction

OR

V2O5 oxidizes SO2 in first reaction AND VO2 reduces O2 in second reaction

OR

vanadium returns to original oxidation state «after reaction»

 

provides an alternative reaction pathway/mechanism «with a lower activation energy» ✔

 

Do not accept “reactants adsorb onto surface AND products desorb”.

Accept “oxidation number” for “oxidation state”.

[2 marks]

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