question_answer

Oxidation number of sulphur in \[{{H}_{2}}{{S}_{2}}{{O}_{8}}\] is

A) \[+6\]                                   

B)        \[+8\]

C)        \[+21\]                                

D)        \[+7\]

Correct Answer: A

Solution :

(i) Draw the structure of oxyacid \[({{H}_{2}}{{S}_{2}}{{O}_{8}})\] to decide the oxidation state of oxygen. Peroxide linkage has \[-1\] oxidation state and normally oxygen has \[-2\] oxidation state. \[\therefore \]Two oxygens form peroxide linkage. \[\therefore \]Oxidation state of two oxygens is \[-1\] each and rest of the six oxygens have \[-2\] oxidation state each,                 \[{{H}_{2}}{{S}_{2}}{{O}_{8}}\]                 \[+1\times 2+2x+\overset{{{H}_{2}}{{S}_{2}}{{O}_{8}}}{\mathop{(-1\times 2)}}\,+(-2\times 6)=0\] or            \[2+2x-2-12=0\] or                                \[2x=12\] \[\therefore \]                        \[x=+6\]