How Do you do This - Chemistry?

Question

Question:
Find the number of moles [AFTER Reaction] of KBrO3 after the reaction.

Given and Calculated:

I3(-) + 2S2O3^2(-) ---> 3I- + S4O6^2(-)

BrO3(-) + 9I(-) + 6H3O(+) ---> Br(-) + 3I3(-) + 9H20
(both equations are given and balanced)
Nh3OHCl:
concentration = 0.020 M
Volume used in each reaction = 10mL

KBrO3:
concentration = 0.020 M
volume used in each reaction = 20 mL

Na2S2O3:
concentration: 0.100M
flask 1:
inital burette reading: 0 mL
final burette reading: 13.2 mL
flask 2:
inital burette reading: 13.2 mL
final burette reading: 26.2 mL
flask 3:
inital burette reading: 26.2 mL
final burette reading: 40.3 mL

My teacher said...
"From the titration the number of moles of triiodide is determined. From the number of moles of triiodide and the two balanced equations above, the number of moles of excess bromate is determined.

Subtracting the number of moles of excess bromate from the total number of moles of bromate used, gives us the number of moles of bromate consumed in the reaction.

i have no idea how to do that...
can some please tell me how..

Greatly appreciated

Answer 1

My suggestion use v1v1=v2m2 to have equal concentration. to get moles get molar mass and you must always balance ur equation. By doing so you know your moles. say you have 2OH then your moles are (2)/(17) therefore moles of OH equals 0.118M of OH.

Answer 2

if this helps, all i remember from my 8th grade science class its something times 6.02 to the 31 power