Question

titration of the I2 produced from 0.1168g of primary standard KlO3 required 27.17 ml of sodium thiosulfate

IO3- + fI- +^H ----> 3I2 +3H2O

I2 +2S2O2^2- ----> 2I- + S4O6^2-

calculate the concentration of the Na2S2O3

Answer 1

Molar mass of KIO3 = 214.001 g/mol

0.1168 gm of KIO3 = 0.1168 / 214 = 5.4579 e-4 Mole

According to equation 1 Mole of KIO3 will produce 3 Moles of I2

5.4579 e-4 Mole of KIO3 will produce 3 x 5.4579 e-4 = 0.00163738 Moles of I2

According to equation 1 Mole of I2 reacts with 2 Moles Na₂S₂O₃

0.00163738 Moles of I2 needs 0.00163738 x 2 = 0.0032747 Moles of Na₂S₂O₃

Volume of Na₂S₂O₃ used = 27.17 ml

Concentration of Na₂S₂O₃ = 0.0032747 x 1000 / 27.17 = 0.1205 M

Concentration of Na₂S₂O₃ = 0.1205 M