An anyhdrous metal chloride, X, contains 37.4% Cl. X is a reducing agent, 0.895 g requiring 23.60 cm^3 of 0.100M KIO3 for complete oxidation in 3- 9M HCl. X reacts with potassium chloride to form an adduct Y, containing 14.8% K. Identify X and Y, and comment briefly on their stereochemistry. Write equations for all reactions and state how you would determine the endpoint of the iodate titration.
I worked out X to be SnCl2 and found the reaction ratio with KIO3 to be 2:1, so the equation is 2snCl2 + KIO3 + 6H+ + 6Cl- --> KICl2 + 2SnCl4 + 3H2O
I then found Y to be KSnCl3
I don't know what stereochemistry means or what to write about X and Y, and I don't know about the endpoint. Is what I have done so far correct?
...hmmmm are you a Durham Chemistry Student?
Yes, I think you are ok. I'm almost positive that compound X is SnCl2 and compound Y is KSnCl3. The percentages work out ok for those two compounds, too. Stereochemistry means the spatial arrangement. The best evidence I can find points to a planar arrangement for SnCl2 and a pyramidal arrangement for the SnCl3^- ion (the KSnCl3 compound probably is ionic). As for the titration, I would think along the lines of potentiometric or polarographic. I am dubious of the equation you have written; what evidence do you have that the IO3^- is reduced to the IO^- ion and not to I2. I would have expected IO3^- to be reduced to I2 and Sn+2 to be oxidized to Sn^+4; however, that doesn't give the correct ratio for the moles IO3^- to mols Sn^+2 to be
SnCl2 for compound X.
I am not sure about the equation either. Obviously if I2 was being produced in the titration then the end point could be tested with starch, but the compounds I have found seem to be right according to the percentages, so I'm not sure what else the equation could be.
Yes, what you have done so far is correct.
First, let's address the stereochemistry part. Stereochemistry refers to the arrangement of atoms in a molecule in three-dimensional space. It includes the study of stereoisomers, which have the same connectivity but differ in their spatial arrangement.
In the context of this question, since X and Y are described as adducts and contain chloride ligands, it suggests that they may have some stereochemistry. However, without further information, it is difficult to determine the exact stereochemistry of X and Y. But it is worth noting that the presence of a chiral center or a coordination complex with different possible isomers could indicate stereochemistry.
Moving on, you correctly identified X as SnCl2 (tin(II) chloride) based on the given information that it's an anhydrous metal chloride and contains 37.4% chlorine.
You also determined the balanced equation for its reaction with KIO3 to be:
2SnCl2 + KIO3 + 6H+ + 6Cl- --> KICl2 + 2SnCl4 + 3H2O
This equation shows that two moles of SnCl2 react with one mole of KIO3 to form one mole of KICl2 and two moles of SnCl4.
Next, you correctly determined Y to be KSnCl3, which is an adduct formed by the reaction of SnCl2 with potassium chloride (KCl).
Now, let's discuss the endpoint of the iodate titration. In this titration, you are using a solution of KIO3 to react with SnCl2. The reaction is initially slow until all the SnCl2 is oxidized to SnCl4. At this point, any excess KIO3 will remain unchanged and can be detected by an indicator.
To determine the endpoint, you can use a starch indicator. Starch forms a deep blue complex with iodine (I2). Initially, when I2 is not yet present, the starch solution will be colorless. As soon as all the SnCl2 is oxidized to SnCl4, I2 will be generated, and the starch indicator will form a blue complex with the iodine, indicating the endpoint.
To summarize, you have correctly identified X as SnCl2 and Y as KSnCl3. You have also determined the balanced equation for the reaction between X and KIO3. While the specific stereochemistry of X and Y cannot be determined without additional information, it is worth considering the possibility of stereochemistry due to the presence of chloride ligands. Lastly, the endpoint of the iodate titration can be determined using a starch indicator, which will change from colorless to blue once all the SnCl2 is oxidized.