OCR A-Level Chemistry Periodic table, elements and physical chemistry (01), June 2023: Question 14

1 mark · Medium difficulty · Multiple Choice

Identify the correct statements regarding the anti-cancer complex cisplatin, Pt(NH3)2Cl2, involving bond angles, oxidation number, and stereoisomerism.

Practise this question

Question

Multiple choice question 14 asking to identify correct statements about the anti-cancer complex Pt(NH3)2Cl2 from three numbered options: 1. It has bond angles of 90 degrees. 2. The oxidation number of Pt is +4. 3. It forms both optical and cis-trans isomers. Four lettered options are given: A (1, 2 and 3), B (Only 1 and 2), C (Only 2 and 3), and D (Only 1).
Question text

14 Which statement(s) is/are correct for the anti-cancer complex Pt(NH3)2Cl2?

1 It has bond angles of 90º.

2 The oxidation number of Pt is +4.

3 It forms both optical and cis-trans isomers.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer [1]

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer for question 14 is D.

14 D 1 AO1.2

How to answer it

Properties of the Anti-Cancer Complex Cisplatin

What this question tests

This question assesses your knowledge of transition metal complex coordination numbers, square planar geometry, bond angles, oxidation state determination, and stereoisomerism (specifically cis-trans and optical isomerism) using the classic anti-cancer drug cisplatin, Pt(NH₃)₂Cl₂ .

Question 14 Breakdown

Evaluating Statements about Pt(NH₃)₂Cl₂

✅ Correct Answer: D (Only 1)

Only statement 1 is correct. Cisplatin is a square planar platinum(II) complex, which possesses bond angles of 90°.

💡 Key Knowledge: Statement 1 (True)

Coordination number 4 complexes can form tetrahedral or square planar shapes. Platinum(II) (a d⁸ metal ion) exclusively forms square planar complexes with bond angles of exactly 90°.

❌ Common Errors: Statement 2 (False)

Students frequently miscalculate the oxidation state of Pt. Since each ammonia ( NH₃ ) is neutral (0) and each chloride ( Cl⁻ ) is -1, Platinum is in the +2 state, not +4. The complex is Pt(II) , not Pt(IV) .

🧠 Exam Technique: Statement 3 (False)

Be careful with isomerism categories! While cisplatin exhibits cis-trans (geometrical) isomerism because it is square planar, it does not exhibit optical isomerism because it possesses a plane of symmetry.

Examiner Note: Multiple-choice questions testing transition metals often combine geometry, oxidation states, and stereoisomerism into three statements. Top-scoring students systematically check each statement individually rather than guessing based on familiar drug names.

Topics

Module 5: Physical chemistry and transition elements · 5.3 Transition elements

Question and mark scheme from the OCR A-Level Chemistry examination, Periodic table, elements and physical chemistry (01), June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.