A 0.7785 g sample containing hydrazine (N2H4, rocket fuel) was dissolved and diluted to 250.0 mL in a volumetric flask.  A 25.00 mL aliquot was treated with 50.00 mL of 0.0313 M KBrO3, which reacts with hydrazine as follows: 2KBrO3 + 3N2H4 ---> 2 KBr(aq) +3 N2(g) +6H2O   The solution was then acidified after adding additional Br-, which converted the excess BrO3- to Br2.   BrO3- + 5Br- + 6H+ -----> 3Br2 + 3H2O   The bromine was then reacted with excess I-.   Br2 + 3I- -----> I3- + 2Br-   The liberated I3- was then titrated with 0.1115 M thiosulfate, HS2O32-, requiring 10.76 mL to reach and endpoint.  Calculate the weight percent hydrazine in the sample.   I3- +  2HS2O3- _---> 3I- + 2H+ +  S4O62-

A 0.7785 g sample containing hydrazine (N₂H₄, rocket fuel) was dissolved and diluted to 250.0 mL in a volumetric flask.  A 25.00 mL aliquot was treated with 50.00 mL of 0.0313 M KBrO₃, which reacts with hydrazine as follows:

2KBrO₃ + 3N₂H₄ ---> 2 KBr(aq) +3 N₂(g) +6H₂O

The solution was then acidified after adding additional Br^-, which converted the excess BrO₃^- to Br₂.

BrO₃^- + 5Br^- + 6H⁺ -----> 3Br₂ + 3H₂O

The bromine was then reacted with excess I^-.

Br₂ + 3I^- -----> I₃^- + 2Br^-

The liberated I₃^- was then titrated with 0.1115 M thiosulfate, HS₂O₃^2-, requiring 10.76 mL to reach and endpoint.  Calculate the weight percent hydrazine in the sample.

I₃^- +  2HS₂O₃^- _---> 3I^- + 2H⁺ +  S₄O₆^2-