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Date	May 2017	Marks available	2	Reference code	17M.3.sl.TZ1.9
Level	SL	Paper	3	Time zone	TZ1
Command term	Outline	Question number	9	Adapted from	N/A

Question

Antimony oxide is widely used as a homogeneous catalyst in the reaction of benzene-1,4-dicarboxylic acid with ethane-1,2-diol in the production of polyethylene terephthalate (PETE) shown below.

Catalysts reduce the activation energy. Outline how homogeneous catalysts are involved in the reaction mechanism.

[1]

Suggest why it is important to know how catalysts function.

[1]

Antimony and its compounds are toxic, so it is important to check that the catalyst is removed from the final product. One technique to detect antimony is Inductively Coupled Plasma Mass Spectroscopy (ICP-MS).

Outline the nature of the plasma state and how it is produced in ICP-MS.

[2]

Markscheme

combine with reactants to form a «temporary» activated complex/intermediate
OR
consumed in one reaction/step AND regenerated in a later reaction/step

[1 mark]

can modify/improve the catalyst/reaction «by making logical predictions»
OR
science relies on models to understand physical reality

Accept other reasonable, relevant answers.

Accept "to predict/select

[1 mark]

electrons AND positive ions «in gaseous state»

high frequency/alternating current passed through argon
OR
«oscillating» electromagnetic/magnetic field
OR
high frequency radio waves

Accept “gas” instead of “argon”.

[2 marks]