25 ml of H_(2)O_(2) solution were added to excess of acidified KI solution. The iodine so liberated required 20 ml of 0.1 N Na_(2)S_(2)O_(3) solution. Calculate strength in terms of normality and percentage.

25 ml of H_(2)O_(2) solution were added to excess of acidified KI solu

1.	25 ml of H_(2)O_(2) solution were added to excess of acidified KI solution. The iodine so liberated required 20 ml of 0.1 N Na_(2)S_(2)O_(3) solution. Calculate strength in terms of normality and percentage.
Answer» 0.04 N, `0.136%` 0.08 N, `0.136%` 0.08 N, `0.163%` 0.02 N, `0.163%` Solution :`O_(2)^(-)+2E^(-) rarr 2O^(-2),"" 2I^(-) rarr I_(2)+2e^(-)` `2(S^(+2))_(2) rarr (S^(+5//2))_(4)+2e^(-), I_(2)+2e^(-) rarr 2I^(-)` Meq. Of `H_(2)O_(2)=` Meq. of `I_(2)=` Meq. of `Na_(2)S_(2)O_(3)` `w/(34//2) times 1000=20 times 0.1` `therefore W_(H_(2)O_(2))=0.034 gr//25ml` `therefore N_(H_(2)O_(2))=0.034/(34//2) times 1000/25=0.08` Vol. STRENGTH `=5.6 times 0.08=0.448` % strength `=17/56 times 5.6 times 0.08=0.136%`