Data response Example 9

 Data Response question on cis-platin

 Teacher only box

I have made up this question to help prepare students for the data response questions which appear on Section A of Paper 3 for the examinations on the 2014 programme (i.e. for examinations after May 2016). The information given is new to the students but they should be able to use their knowledge and understanding of the chemistry content of the programme to answer the questions. Because I have tried to make the chemistry interesting it may be a little harder than an actual exam question but exposure to questions like this beforehand should make students able to face the data response question in the final examination with considerable confidence. Since some of the answers require a knowledge and understanding of material from the AHL this particular question is only suitable for Higher Level students.

As well as including model answers I have also explained the chemistry fully and given the 'Complete course for students' links to the pages which cover the theory behind each individual question. If you set it as an assigned task using Student Access, students will not be able to see the model answers until after they have submitted their answers to you. If you simply give students access to the page (rather than assigning it as a task) they will be able to access the model answers themselves for review/revision/self-study etc.

If you do not wish to use student access, links to downloadable versions of the questions and, separately the worked answers, can be found at Printable versions of written tasks.

 

 

Cis-platin, Pt(NH3)2Cl2, is used to treat a variety of cancers including testicular and ovarian cancer. The compound was discovered in 1845. It is mIB Docs (2) Teamfactured from potassium tetrachloroplatinate, K2PtCl4. The process goes through several stages to give an overall yield of cis-platin of 63%.

(a) Calculate the mass of potassium tetrachloroplatinate required to produce 100.0 g of cis-platin. [2]

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(b). Cis-platin contains four monodentate ligands.

(i) Deduce the oxidation state of platinum in cis-platin. [1]

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(ii) State the meaning of the term monodentate ligand with reference to cis-platin. [2]

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(iii) Show how the name cis-platin leads to the deduction that the shape of the compound is square planar. [1]

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(c) The pharmaceutical properties of cis-platin were only discovered accidently in 1965 when scientists at Michigan State University were investigating the effect of electric fields on bacteria cell division. They realised that when a platinum electrode was used a compound was formed (later shown to be cis-platin) that stopped the bacteria dividing.

State the single word used to describe a chance happening that leads to a discovery. [1]

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(d) Cis-platin has no overall charge so it can diffuse through the membrane of cancer cells. Once inside the cell it exchanges a chloride ion for a water molecule to form a new square planar species. This new species can enter the cell nucleus where it exchanges another chloride ion and also the water molecule so that it can bind to the nitrogen atoms on two different guanine molecules in the cell’s DNA. This alters the cancer cell’s DNA and prevents it from reproducing.
 

(i) Deduce the formula of the new square planar species formed when one of the chloride ions on cis-platin is exchanged for a water molecule. [1]

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(ii) Suggest one reason why trans-platin is ineffective as a treatment against cancer. [1]

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