Question

You are given the equation: AgBr + 2S₂O₃^2- ---> Ag(S₂O₃)₂^3- + Br ^-

What mass of AgBr can be dissolved by 750 mL of 0.300 M Na₂S₂O₃?

I know that the answer is 21.1 g AgBr, but I am not sure how you get to this point. (What are the steps to get this answer?)

Answer 1

AgBr + 2S2O32-     --->   Ag(S2O3)23- + Br -

from this equation it is clear that for 2 moles of 2S2O3^2- one mole of AgBr required

first calculate the moles of Na2S2O3 from the given data using following formula

Molarity = no of moles / volume in liters

no of moles = molarity x volume in liters

no of moles = 0.3 x 0.75 L

= 0.225 moles

from the equation it is clear that for 2 moles 1 mole of AgBr

for 0.225 moles 0.1125 moles AgBr required

now convert 0.1125 moles in to weight using the following formula

moles = weight of AgBr / molar mass of AgBr

weight = moles of AgBr x molar mass of AgBr

= 0.1125 x 187.77

= 21.1241 grams