Question detail
What is the role of ligands in the formation of complex ions?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Transition metals (A-level only)
Question
- A. To provide electrons to the metal ion
- B. To stabilize the metal ion
- C. To increase the oxidation state of the metal ion
- D. To decrease the coordination number
Answer
To provide electrons to the metal ion
Explanation
The correct option is To provide electrons to the metal ion. To provide electrons to the metal ion is the best answer because it directly supports the AQA A-Level Chemistry objective to use equations to represent ligand substitution. This reasoning is anchored to Complex ions and ligand substitution (A-level only) in Transition metals (A-level only), and it separates ligand from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.
Common mistake
Incorrect Representation of Ligand Substitution
Students often write ligand substitution reactions without balancing the equation or including the correct charges on the ions involved.
To fix this, always ensure that the equation is balanced and that the charges on the complex ions and ligands are correctly represented. For example, in the substitution of water by ammonia in [Cu(H2O)6]²⁺ to form [Cu(NH3)4(H2O)2]²⁺, write the balanced equation: [Cu(H2O)6]²⁺ + 4NH3 → [Cu(NH3)4]²⁺ + 2H2O.
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