CBSE Class 12 Chemistry Question Bank with Important Questions – Coordination Compounds VBT & CFT 2026
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Introduction
As we approach the board exam season, students often find themselves overwhelmed by the vastness of the syllabus. Among all the chapters, Coordination Compounds stands out as a high-scoring yet conceptually dense unit. For the upcoming academic cycle, having a reliable CBSE Class 12 Chemistry Question Bank 2026 is not just a luxury; it is a necessity. This chapter contributes significantly to the 70-mark theory paper, with a weightage typically around 7 marks.
The core of this chapter lies in understanding how metal ions interact with ligands to form complex structures. Two pivotal theories—Valence Bond Theory (VBT) and Crystal Field Theory (CFT)—form the backbone of this unit. In this guide, we provide a comprehensive analysis of these theories, repeated exam questions, and the medical significance of these compounds to help you rank high in your preparations.
CBSE Class 12 Chemistry Question Bank 2026: VBT and CFT Explained
Understanding the bonding in coordination complexes is essential for solving numerical and descriptive questions. The CBSE Class 12 Chemistry Question Bank 2026 focuses heavily on the application of these two theories.
Valence Bond Theory (VBT)
VBT explains the formation, geometry, and magnetic behavior of complexes through the concept of hybridization. According to this theory, the central metal atom or ion makes available a number of vacant s, p, and d orbitals equal to its coordination number.
Key Geometries to Remember:
sp³: Tetrahedral
dsp²: Square Planar
d²sp³: Inner Orbital Octahedral
sp³d²: Outer Orbital Octahedral
Crystal Field Theory (CFT)
CFT is a more modern approach that treats the metal-ligand bond as purely electrostatic. It explains the splitting of degenerate d-orbitals into different energy levels (t2g and eg) when ligands approach.
Octahedral Splitting: The d-orbitals split into a lower energy t2g set and a higher energy eg set.
Tetrahedral Splitting: The pattern is reversed, with e orbitals at lower energy and t2 orbitals at higher energy.
Spectrochemical Series: A crucial part of CFT is the arrangement of ligands in increasing order of their field strength. This determines whether a complex will be high-spin (weak field ligands) or low-spin (strong field ligands).
Important Formulas and Terms in Coordination Chemistry
To excel in the CBSE Class 12 Chemistry Question Bank 2026, students must be well-versed with the terminology and calculation methods. While detailed derivations are less common, knowing the application of these concepts is vital.
Concept | Description / Formula Name |
Oxidation State | Calculating the charge on the central metal ion. |
Coordination Number | Total number of ligand donor atoms bonded to the metal. |
Effective Atomic Number (EAN) | Rule to predict the stability of metal complexes. |
Magnetic Moment | Spin-only formula involving the number of unpaired electrons. |
Crystal Field Splitting Energy (CFSE) | Calculation of stabilization energy for d-configurations. |
Repeated Questions from Previous Years (2016–2025)
Analyzing past papers is the most effective way to identify "sure-shot" questions. The following questions have appeared frequently in various sets:
IUPAC Nomenclature: Write the IUPAC names for complexes like K3[Fe(C2O4)3] and [Co(NH3)5Cl]Cl2.
Magnetic Behavior: Why is [Ni(CN)4]^2- diamagnetic while [NiCl_4]^2- is paramagnetic? (Explain using VBT).
Color of Complexes: Explain the violet color of [Ti(H_2O)_6]^3+ using CFT and d-d transitions.
Isomerism: Draw the structures of optical isomers of [Co(en)_3]^3+ and geometrical isomers of [Pt(NH3)2Cl2].
Spectrochemical Series: Arrange the ligands F^-, CN^-, H_2O, and en in increasing order of crystal field splitting energy.
Medical Applications of Coordination Compounds
Coordination chemistry isn't just limited to laboratory experiments; it plays a critical role in human health and medicine. High-scoring answers in 2026 often include these real-world applications:
Cancer Therapy: Cis-platin is a neutral coordination complex used in chemotherapy to inhibit the growth of tumors by binding with DNA.
Heavy Metal Poisoning: Chelating agents like EDTA are used to treat lead poisoning by forming stable, soluble complexes that the body can excrete.
Biological Systems: Hemoglobin: A coordination compound of iron (Fe^2+) responsible for oxygen transport.
Vitamin B12: A cobalt complex essential for nerve function and red blood cell production.
Chlorophyll: A magnesium complex vital for photosynthesis.
CBSE Class 12 Chemistry Question Bank 2026: Preparation Strategy
To rank high and secure a 95+ score in Chemistry, follow these steps:
Master IUPAC Rules: This is a guaranteed 2-mark section.
Conceptual Clarity on Ligands: Differentiate between unidentate, didentate, and ambidentate ligands.
Practice VBT Diagrams: Learn to draw the orbital occupancy for various hybridizations.
Use Official Resources: Always refer to the official question banks provided by boards for the most accurate exam pattern.
Official Links for Study Resources
CBSE Official Academic Portal: cbseacademic.nic.in
Official Link : https://www.cbse.gov.in/cbsenew/question_bank.html
Conclusion
Mastering Coordination Compounds requires a blend of logical reasoning and factual knowledge. By focusing on VBT, CFT, and the IUPAC nomenclature provided in this CBSE Class 12 Chemistry Question Bank 2026, you are setting yourself up for success. Remember, consistency is the key to mastering complex chemical bonding.
Frequently Asked Questions (FAQs)
Q1: Where can I find the official CBSE Class 12 Chemistry Question Bank 2026?
A1: The official question banks are released on the CBSE academic website. Additionally, for state-specific resources like Maharashtra Board, you can visit the SCERT portal.
Q2: Which is more important for the exam, VBT or CFT?
A2: Both are equally important. VBT is usually asked for geometry and hybridization, while CFT is asked for explaining color, magnetic properties, and CFSE calculations.
Q3: How do coordination compounds help in the medical field?
A3: They are used in chemotherapy (Cis-platin), as chelating agents for treating metal toxicity (EDTA), and occur naturally in the human body as life-sustaining molecules like Hemoglobin.
Q4: Is the CBSE Class 12 Chemistry Question Bank 2026 different from previous years?
A4: While the core syllabus remains similar, the 2026 bank emphasizes competency-based questions and case-study problems more than rote memorization.
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