The concentration of an aqueous solution of NaOCl (sodium hypochlorite; the active ingredient in household bleach) can be determined by a redox titration with iodide ion in acidic solution:

Assume that the blue spheres in the buret represent I-ions, the red spheres in the flask represent OCl-ions, the con-centration of the I-ions in the buret is 0.120 M, and the volumes in the buret and the flask are identical. What is the concentration of NaOCl in the flask? What percentage of the I-solution in the buret must be added to the flask to react with all the OCl-ions?

Video transcript

Hello everyone today we have the falling problem. The concentration of iron chloride in aqueous solution was determined by redox filtration with potassium chrome eight. The sample was first dissolved in hydrochloric acid to make the solution acidic. The working reaction is shown below. And this is our chemical formula or reaction here in the diagram below. The crow made ions are depicted in green spheres and the iron two plus ions are depicted in orange spheres. In the puree, the concentration of chromium ions is 20.170 moller. The volumes in the berry and the flask are the same. So the volumes are the same, calculate the concentration of the iron chloride in the solution and determine the percentage of the chrome eight that must be added in order to react with all of the iron two plus reactant. So the first you want to do is you want to take into account the ions that are in both the beret and the flask. So if we count each individual molecule and we know that green represents iron. We can say that the Beret has chrome ions and the flask has iron two plus ions. So this right here is our flask and this is our beret. And so according to the question according to the question information, our concentration of chrome eight ions Is two times that of the concentration of our iron. So we see we have 12 iron atoms and then we have 24 chromium atoms. So we have twice as many chrome eight. Then we do iron atoms. And so what we can do is essentially rearrange his equation to calculate for the concentration of iron atoms and we get the concentration for chrome eight ions, which is 80.170 divided by two giving us 0.0850 Moller. And this is going to be the first part of our answer. And so the second part is going to be finding out the percentage of chromium ions that must be added to react with all of the iron two plus ions. So we have our balanced chemical equation here. And so what we need to make note is that when we have one Chrome 8 to -1 And we see that we have one because the coefficient in front of the Chrome eight and the reaction is one. This reacts with six iron, two plus ions and this is denoted by the six as the coefficient in the chemical reaction. And so we also know that the concentration of chrome is twice that of iron. So what we can do is we can set up the equation That we have 1/6, we have one curl mate per every six iron. And we also have One crow mate for every two iron. And when we figure this out and we solve it we get 1/12 which is equal to 0.833. And we multiply that by 100 because we did a percentage, we get 8.33% as our final answer. And with that we have answered the question overall. I hope this helped, and until next time.