The amount of I₃⁻(aq) in a solution can be determined by titration with a solution containing a known concentration of S₂O₂⁻³(aq) (thiosulfate ion). The determination is based on the net ionic equation 2S₂O₃²⁻(aq)+I₃⁻(aq)⟶S₄O₆²⁻(aq)+3I⁻(aq). Given that it requires 38.1 mL of 0.440 M Na₂S₂O₃(aq) to titrate a 25.0 mL sample of I₃⁻(aq), calculate the molarity of I₃⁻(aq) in the solution.

Respuesta :

Answer: 0.22 M

Explanation:

[tex]2S_2O_3^{2-}(aq)+I_3^-\rightarrow S_4O_6^{2-}(aq)+3I^-(aq)[/tex]

Molarity of a solution is defined as the number of moles of solute dissolved per Liter of the solution.

[tex]Molarity=\frac{moles}{\text {Volume in L}}[/tex]

moles of [tex]Na_2S_2O_3=Molarity\times {\text {Volume in L}}=0.440\times 0.025=0.011moles[/tex]

[tex]Na_2S_2O_3\rightarrow 2Na^+S_2O_3^{2-}[/tex]

Thus moles of [tex]S_2O_3^{2-}[/tex] = 0.011

According to stoichiometry:  

2 moles of [tex]S_2O_3^{2-}(aq)[/tex] require 1 mole of [tex]I_3^[/tex]

Thus 0.011 moles of [tex]S_2O_3^{2-}(aq)[/tex] require=[tex]\frac{1}{2}\times 0.011=5.5\times 10^{-3}[/tex] moles of [tex]I_3^-[/tex]

Thus Molarity of [tex]I_3^-=\frac{5.5\times 10^{-3}}{0.025L}=0.22M[/tex]

Therefore, the molarity of [tex]I_3^-[/tex] in the solution is 0.22 M