MCQ practice · SSC Chemistry Board questions · Chapter 7: Chemical Reactions
How many spectator ions are there in the reaction 2FeCl₂ + Cl₂ → 2FeCl₃?
Think it through first, then pick an option.
- a 6
- b 4
- c 3
- d 2
Answer and explanation
Correct answer: b 4
The 4 Cl⁻ of 2FeCl₂ do not change in the reaction, so they are spectators.
Why the other options are wrong
- a 6: 6 is the total Cl⁻ in the product; 2 came newly from Cl₂, so 4 are spectators.
- c 3: Each FeCl₃ has 3 Cl, but 4 Cl⁻ were there from the start; the answer is 4.
- d 2: The 2 new Cl⁻ come from Cl₂ and took part; the spectators are 4.
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