OCR A-Level Chemistry Periodic table, elements and physical chemistry (01), June 2018: Question 15

1 mark · Medium difficulty · Multiple Choice

Identify the correct statements regarding the stereochemistry, bond angles, and isomerism of the platinum complex Pt(NH3)2Cl2.

Practise this question

Question

Multiple choice question 15 asks which statements are correct for the complex Pt(NH3)2Cl2. Three statements are listed: 1. One of its stereoisomers is used as an anti-cancer drug. 2. It has bond angles of 109.5 degrees. 3. It has optical isomers. Four options A, B, C, D are provided below.
Question text

15 Which statement(s) is/are correct for the complex Pt(NH3)2Cl2?

1 One of its stereoisomers is used as an anti-cancer drug.

2 It has bond angles of 109.5°.

3 It has optical 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 The mark scheme table shows the correct answer for question 15 is D.

15 D 1 AO1.1

Total 15

SECTION B

How to answer it

Properties of Square Planar Platinum Complexes (Cisplatin)

What this question tests

This question assesses your knowledge of transition metal stereochemistry, specifically coordination number, geometrical (cis-trans) isomerism, optical isomerism, molecular shape, and bond angles in square planar complexes, alongside real-world applications in medicine (anti-cancer drugs).

Question 15 Analysis

Evaluating Statement 1, 2, and 3 for Pt(NH₃)₂Cl₂

✅ Correct Answer: D (Only 1)

The correct option is D because only statement 1 is scientifically accurate for the neutral complex Pt(NH₃)₂Cl₂ .

💡 Key Knowledge: Statement 1

  • Pt(NH₃)₂Cl₂ exists as two geometrical isomers: cis and trans.
  • The cis-isomer is known as cisplatin, a vital anti-cancer drug used in chemotherapy that binds to DNA to inhibit replication.

❌ Why Statement 2 is Wrong

  • Platinum(II) complexes with 4 coordinate bonds (like this one) adopt a square planar geometry, not tetrahedral.
  • The bond angles in a square planar complex are 90° (and 180° for trans positions), not 109.5° (which is tetrahedral).

❌ Why Statement 3 is Wrong

  • Square planar complexes of the type Pt(NH₃)₂Cl₂ have a plane of symmetry passing through the central metal atom and all four ligands.
  • Because they are planar and possess a plane of symmetry, they are superimposable on their mirror images and do not show optical isomerism.

🧠 Exam Technique

When tackling multiple-choice questions involving statements:

  1. Evaluate each statement independently before looking at the options A-D.
  2. Recall shape rules: Pt(II) and Pd(II) heavily favor square planar coordination numbers of 4.
  3. Eliminate options rapidly once you identify a definitive false statement (e.g., knowing bond angles are 90° immediately rules out statements containing 2).
Mark Scheme Note: 1 mark awarded for selecting D. AO1.1 (Demonstrating knowledge and understanding of scientific ideas).

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 2018. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.