Calculate the molarity of thiosulfate solution if 0.400mg of Kl03 required 100ml of the thiosulfate solution provided that excess kl and hcl were added.

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To calculate the molarity of the thiosulfate solution, we need to know the volume (in liters) and the number of moles of thiosulfate dissolved in that volume.

From the given information, we know that 0.400 mg of KIO3 required 100 mL of the thiosulfate solution. Firstly, we need to convert the mass to moles using the molar mass of KIO3.

The molar mass of KIO3 can be calculated by adding up the atomic masses of each element:
Potassium (K) = 39.1 g/mol,
Iodine (I) = 126.9 g/mol,
Oxygen (O) = 16.0 g/mol.

So, the molar mass of KIO3 is:
39.1 + (3 x 126.9) + (3 x 16.0) = 214.9 g/mol.

Next, we can convert the mass of KIO3 to moles using the formula:
moles = mass / molar mass.

In this case, the mass is 0.400 mg (0.400 x 10^-3 g). Therefore, the number of moles of KIO3 is:
moles = 0.400 x 10^-3 g / 214.9 g/mol.

Now, we know the number of moles of KIO3. Based on the balanced chemical equation between KIO3 and thiosulfate (Na2S2O3), we can determine the stoichiometry of the reaction.

However, since we have been informed that excess KI and HCl were added, the KIO3 was not the limiting reagent in the reaction, which means every mole of KIO3 reacted with an equal number of moles of thiosulfate (Na2S2O3). Hence, the number of moles of thiosulfate is also equal to the number of moles of KIO3.

Lastly, we can calculate the molarity (M) of the thiosulfate solution using the formula:
M = moles / volume.

Given that the volume is 100 mL (0.100 L), we can substitute in the values:
M = moles / 0.100 L.

Therefore, the molarity of the thiosulfate solution can be calculated by dividing the number of moles of KIO3 (determined earlier) by 0.100 L.