MCQ practice · SSC Chemistry Board questions · Chapter 7: Chemical Reactions
What is the oxidation number of sulphur in oleum?
Think it through first, then pick an option.
- a 0
- b + 2
- c + 4
- d + 6
Answer and explanation
Correct answer: d + 6
Oleum is H₂S₂O₇: 2(+1) + 2x + 7(−2) = 0, so 2x = 12 and x = +6.
Why the other options are wrong
- a 0: 0 is for free sulphur; oleum is the compound H₂S₂O₇.
- b + 2: +2 is in thiosulphate; for H₂S₂O₇, 2(+1) + 2x − 14 = 0.
- c + 4: +4 is in sulphite (H₂SO₃); in oleum x = +6.
More board questions on this topic
- What is the oxidation number of hydrogen in CaH₂?
- What is the oxidation number of hydrogen in LiAlH₄?
- What is the oxidation number of oxygen in a peroxide compound?
- What is the oxidation number of oxygen in NaO₂?
Your account is open, so all 30,000+ MCQs from every chapter are yours. Start practising SSC Chemistry →
Want to keep going?
A free account carries you on to the next questions and opens 30,000+ MCQs from every chapter. Join before launch and Chirkut bundles are 60% off.
The ones you missed, worth one more look