What Is the Identity of Metal M in M(ClO)2 Based on Iodometric Titration Data?

[jesse1256]

Redox Titrations Bleach! help!

Homework Statement

An unknown metal hypochlorite salt, M(ClO)2, is subjected to analysis by iodometric titration: the salt is dissolved in dilute sulfuric acid, treated with excess aqueous KI, and then titrated with Na2S2O3 in the same manner as your experiment. The unknown metal ion (M2+) is completely unreactive in the titration. However, all of hypochlorite ion bondd to the metal reacts completely with Na2S2O3. Iodemetric titration of an acidified 0.0499 g sample of M(ClO)2 required 28.42 ml of 0.05521 mol/L Na2S2O3 to reach the equivalence point. What is the identity of metal M?

Homework Equations

IO3^- + 5I^- + 6H^+ → 3I2 + 3H20
I2 + 2S2O3^2- → 2I^- + S4O6^2-
ClO^- + 2I^- + 2H^+ → I2 + Cl^- + H20

The Attempt at a Solution

So far all I have is the number of moles for Na2S2O3 = 0.001569 mol
I have no idea where to go from there! please help

ALSO one more question

Homework Statement

A sample of Au(ClO)3 is contaminated with LiClO. An acidified 0.2000 g sample of this mixture is treated with excess sodium iodide and subjected to iodometric titration. The sample requires 48.24 mL of 0.08893 mol/L Na2S2O3 to reach the equivalence point. Assuming that the Au^3+ and Li^+ ions are unreactive during the titration, determine the mass percent of LiClO in the sample.

Homework Equations

All the equations used in the first question!

The Attempt at a Solution

Only moles so far. =0.004289 molPleae help. Thanks!

 

[Borek]

So far all I have is the number of moles for Na2S2O3 = 0.001569 mol

User stoichiometry to find out how many moles of ClO^- were present in the sample of the given mass, then use this information to find out molar mass of the metal.

 

[jesse1256]

okay that sounds easy enough, I think the main problem I have is not knowing what equation to use. Or do I set up my own stoichiometric equation adding M(ClO)2. and if I do, how do I go about doing that? Thanks!

 

[Borek]

Forget about using "equations", think about it as just another stoichiometry problem.

All titrations are nothing more but a simple stoichiometry. You know moles of this, you have to calculate corresponding moles of the other.

 

[DeeNos]

Redox titrations, also known as oxidation-reduction titrations, are commonly used in analytical chemistry to determine the concentration of a substance in a sample. In this case, the goal is to identify the unknown metal in the hypochlorite salt M(ClO)2. The titration method used is iodometric titration, which involves the reaction between iodine and thiosulfate.

From the given information, we know that the metal ion M2+ is unreactive in the titration, but all of the hypochlorite ions bonded to the metal react completely with Na2S2O3. This means that the number of moles of hypochlorite ion in the sample is equal to the number of moles of Na2S2O3 used in the titration.

Using the given volume and concentration of Na2S2O3, we can calculate the number of moles of Na2S2O3 used in the titration:

n(Na2S2O3) = (0.02842 L)(0.05521 mol/L) = 0.001569 mol

Since the number of moles of hypochlorite ion is equal to the number of moles of Na2S2O3, we can use the balanced equation for the reaction between hypochlorite ion and iodine to determine the number of moles of hypochlorite ion in the sample:

n(ClO-) = n(Na2S2O3) x (2 moles ClO-/2 moles Na2S2O3) = 0.001569 mol

Now, using the molar mass of ClO- (51.45 g/mol), we can calculate the mass of ClO- in the sample:

m(ClO-) = n(ClO-) x M(ClO-) = (0.001569 mol)(51.45 g/mol) = 0.08069 g

Since we know that the sample weighed 0.0499 g, we can calculate the mass percent of ClO- in the sample:

% mass ClO- = (0.08069 g / 0.0499 g) x 100% = 161.7%

This result is clearly incorrect, as the mass percent should never be greater than 100%. Therefore, we can conclude that there must have been an error in the given information or calculations