Which of the following is a reducing agent?

Options

A. `SeO_(2)`
B. `TeO_(2)`
C. `SO_(2)`
D. `PoO_(2)`

Answer

3

Explanation

Sulpher dioxides is one of the few common gases that is a reducing agent ,itself being easily oxidized to the sulphate ion:
`SO_(2)(aq.)+2H_(2)O(l)rarrSO_(4)^(2-) (aq.) +4H^(+) (aq.)+2e^(-)`
To test for reducing gases,such as sulphur dioxide ,we can use an oxidizing agent that undergoes a colour change, the most convenient one being the dichromate ion. A filter paper soaked in acidified orange dichromate ion will turn green as a result of the formation of the chlormium (III) ion:
`Cr_(2)O_(7)^(2-)(aq.)+14H^(+)(aq.)+6e^(-) rarr 2Cr^(3+)(aq.) +7H_(2)O(l)`