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Determine the quantity (mg/L) of sodium hypochlorite (NaOCl) thatwould be required to oxidize 0.5 mg/L of ferrous ion (Fe2+)according to the following reaction:

2 Fe2+ + NaOCl + 2 H+ ->> 2 Fe3+ + Na+ + H2O + Cl-

I have no idea how to start this problem

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Sixta Kovacek
Sixta KovacekLv2
28 Sep 2019

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Related questions

Equipment Materials

50.00 ml buret, 250.ml volumetric flask, 1.00 ml volumetric pipet 10.0 mL volumetric pipet, 25.00 mL volumetric pipet, pipettor, 250 mL Erlenmeyer flask, 10.0 mL graduated cylinder, several beakers, several watchglasses, unkown bleach solution, 10% potassium iodide solution, 2M hydrochloric acid solution, 0.150 M sodium thiosulfate solution, 1% starch solution.

Background information regarding this experiment is as follows:

An aqueous solution of sodium hypochlorite (NaOCI) is a clear, slightly yellow liquid, and is commonly known as bleach. Aside from its uses as a bleaching agent, sodium hypochlorite solutions are also used as sterlizing agents and in water treatment. Industrial uses include agricultural, food handling, paper production, and textile production. Sodium hypochlorite is also added to waste water to reduce odors.

The concentration of sodium hypochlorite in bleach solutions can be determined by titration. Therefore, we must use a two-step method to titrate sodium hypochlorite. In the first step, sodium hypochlortie, hydrochloric acid, iodide ion, and starch are combined to form a starch-triiodide complex. In this step there are 3 reactions that take place:

The result of these 3 reactions is that when sodium hypochlorite is present the starch-triiodide complex is produced.

In the second step the starch-triiodide product is titrated by sodium thiosulfate to form a colorless solution of iodide, dithionate.

I do not know how to answer the following on the data sheet: (? means I do not know how to answer)

Table 1:

Mass of 1.00 ml of unknown (by tare): 10.552 g

Density of bleach: (g/ml) : 1.055 g/ml

Volume of diluted bleach used in each titration: 10.00

Concentration of sodium thiosulfate: ? (M)

Titration Data:

Initial buret reading (ml): trial1: 0.000 ml Trial 2: 0.00 ml Trial 3: 0.000ml

Final buret reading (ml): trial 1: 13.50ml Trial 2: 13.30ml Trial 3: 13.40ml

Volume delivered(ml: trial 1: ? Trial 2: ? trial 3:?

Calculations: (show clearly)

For trial 1,2,3 ???

1.Moles of Na2S2O3 in titration: ??? trial 1,2,3

2.Moles of NaOCl: ???trial 1, 2,3

3.Average moles of diluted NaOCl: (one answer) ?

4.Average moles of undiluted NaOCl: (one answer.. mol) ?

5.Standard Deviation: (one answer) (mol)

6.Average mass of NaOCl in 25.00mL of undiluted bleach: ? (g)

7.mass of 25.00 mL of undiluted bleach: ? (g)

8. Mass % of NaOCL from experiment: ? (%)

9.Actual mass % of NaOCL (from prof; student does not make an entry):? (%)

More questions all need to be answered please:

1. Calculate the volume of the reagent thiosulafte solution which would be required if you titrated a 25ml sample of the original commercial bleach instead of 25ml of the diluted solution.

2. Why would we choose a graduated cylinder to measure the HCl and KI solutions instead of a volumetric pipette? When would we use a volumetric pippette?

3. You calculated the mass percent of sodium hypochlorite in the bleach( dilute and undiluted). Now calculate the molarity of the sodium hypochlorite in the diulte and undiluted solution/

4. Use oxidation states to show that equations (2) and (4) in the introduction are redox reactions and that equation 1 is not a redox reaction. :

-(1) NaOCl(aq) + HCl(aq) yields HOCl(aq)+NaCl(aq)

-(2) HOCL (aq) + HCl(aq) + 3I(aq) yields I3(aq) + 2CL(aq) + H2O(l)

-(4) (I3) (Starch) + 2S2O3 yields 3I + S4O6 + starch

5. combine equation 1-3 to show the overall reaction for the products of the starch-triiodide complex.

-(1) NaOCl(aq) + HCl(aq) yields HOCl(aq)+NaCl(aq)

-(2) HOCL (aq) + HCl(aq) + 3I(aq) yields I3(aq) + 2CL(aq) + H2O(l)

-(3) I3 + Starch yields (I3) (Starch)

6. What standard was used in this experiment?

7. Describe the naming of NaClO and HClO. What are the names of the following compounds? NaClO2 , NaClO3, NaClO4 , HClO2, HClO3, HClO4

8 Submit a one paged (typed double spaced) report that discusses the following topics:

a. the goals or objectives of the experiment

b.your results as they relate to the goals and objectives

c. the quality of your results.

PLEASE INCLUDE CALCULATIONS

3. Suppose you have the following reagents available under standard conditions (i.e., P- 1 atm for all gases25 °C: C mol L1 for all aqueous species, including H.)

Co(s), Ag (aq), CI(aq), Cr(s), BrO3 (a), 2(s), F(aq)

Consult the standard reduction potentials on the next page and then answer the following questions

(a) Which is the strongest oxidizing agent?

(b) Which is the strongest reducing agent?

PLEASE INCLUDE CALCULATIONS/ FORMULAS

(c) Which of the available reagent(s), if any, will oxidize Cd(s) without oxidizing Pb(s)? If none of the available reagents can be used for this purpose, then identify another reagent from the table that could be used. For one of the reagents you've identified, write down a balanced chemical equation for the reaction that occurs.

Show transcribed image text

I am studying an iron chloride redox battery cell (not a flow battery). It is constructed with an iron negative electrode, a carbon positive electrode with an iron (II) chloride electrolyte. The electrodes are physically isolated from each other in a beaker of iron(II) chloride. This cell can be charged and discharged and will run a motor. The output of the battery is 1.2V and can deliver 0.2A.

Unlike most redox batteries, the positive carbon electrode does not take part in the chemistry. The positive carbon electrode, as far as I understand it, simply provides a reaction site for the positive half reaction.

We are told that the half reaction at the positive electrode converts Fe2+ ions to Fe3+ ions (charge) and back again (discharge).

The half reaction at the negative electrode converts Fe2+ ions to metallic iron (charge) and back again (discharge).

The task is to fully describe the iron chloride redox chemistry at both electrodes during charge and discharge.

Where I am:

I am starting with an assumption that during charge and the application of external electrical energy, the dissociated ions in the electrolyte, Fe2+ and Cl-, must migrate to the oppositely charged electrodes. This would be independent of the electrode material and determined simply by the external EMF applied to the battery during charge. The Fe2+ ions must migrate to the negative electrode while the Cl- ions must migrate to the positive electrode.

The result is that the negative electrode will be surrounded by Fe2+ ions and the positive electrode will be surrounded by Cl- ions.

It seems clear that Fe2+ ions will react with incoming electrons, at the negative electrode, to form metallic iron.

However, I do not understand how any reaction can occur at the positive electrode with respect to any variety of "iron chloride". There should be no Fe2+ ions at the positive electrode. Therefore, no reaction involving Fe2+ ions can occur at the positive electrode.

The positive electrode is carbon surrounded by Cl- ions. It is under the influence of a positive electric potential by the external charge source. The only possible reaction I can see occurring is that the Cl- ions may liberate an electron at the positive electrode to form chlorine gas. However, this is not observed under the charging voltage applied, at 25OC and 1 atm. There are no bubbles or chlorine smell.

I have found various references such as:

https://courses.lumenlearning.com/boundless-chemistry/chapter/electrolysis/

That state:

Oxidation of ions or neutral molecules occurs at the anode, and reduction of ions or neutral molecules occurs at the cathode. For example, it is possible to oxidize ferrous ions to ferric ions at the anode:

(aq)+e−

This is exactly what we are told is happening at the positive electrode but I am unable to see how this can occur.

How can a positive ion be in proximity to the positive electrode in order to react with it?? How can any reaction involving Fe2+ ions happen at the positive electrode??

 

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