Which of the following has $\mathrm{S}-\mathrm{S}$ bond?

• Correct answer
  A

  $\mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_6$
• B

  $\mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_7$
• C

  $\mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_8$
• D

  Mustard gas

Solution

Only $\mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_6$ (thionic acid) contains $\mathrm{S}-\mathrm{S}$ bond. Its structure is

Hence, the correct answer is option: 'A'.