Pyrosulfurous acid
Dithionous acid
The question asks us to identify the oxoacid of sulfur that contains an S-O-S bond. Let's analyze each option to determine the correct answer.
Also known as oleum, pyrosulfuric acid is a compound containing a sulfur-sulfur (S-O-S) bond. Its structure includes two SO3 groups linked via an oxygen atom:
This compound indeed contains the S-O-S linkage, making it the correct answer.
The structure of pyrosulfurous acid theoretically involves a similar concept of two sulfur atoms, but its existence is mainly hypothetical, and it does not traditionally represent an S-O-S bond within stable compounds.
Also called hydrosulfurous acid, its structure does not contain the S-O-S linkage, typically depicting linkage through two reduced sulfur centers.
Dithionic acid contains two sulfur atoms bonded directly to an oxygen atom each, lacking an S-O-S linkage typical of pyrosulfuric acid.
After evaluating all options, Pyrosulfuric acid (H2S2O7) is the only option with the S-O-S bond.
From the given following (A to D) cyclic structures, those which will not react with Tollen's reagent are : 
Compound 'P' undergoes the following sequence of reactions : (i) NH₃ (ii) $\Delta$ $\rightarrow$ Q (i) KOH, Br₂ (ii) CHCl₃, KOH (alc), $\Delta$ $\rightarrow$ NC-CH₃. 'P' is : 

One mole of a monoatomic ideal gas starting from state A, goes through B and C to state D, as shown in the figure. Total change in entropy (in J K\(^{-1}\)) during this process is ............... 
The number of chiral carbon centers in the following molecule is ............... 
A tube fitted with a semipermeable membrane is dipped into 0.001 M NaCl solution at 300 K as shown in the figure. Assume density of the solvent and solution are the same. At equilibrium, the height of the liquid column \( h \) (in cm) is ......... 