MCQ practice · SSC Chemistry Board questions · Chapter 7: Chemical Reactions
What is the oxidation number of sulphur in Na₂S₂O₃?
Think it through first, then pick an option.
- a +4
- b +3
- c +2
- d +1
Answer and explanation
Correct answer: c +2
2(+1) + 2x + 3(−2) = 0, so 2x = 4 and x = +2.
Why the other options are wrong
- a +4: Forgetting there are two S gives +4; 2x = 4, so x = +2.
- b +3: 2x = 4, not 6; x = +2.
- d +1: +1 is the value of Na; for S, x = +2.
More board questions on this topic
- What is the oxidation number of sulphur in Na₂S₂O₃?
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- What is the oxidation number of hydrogen in CaH₂?
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