will someone plz assist me with theses questions please. Determination of Iron B

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will someone plz assist me with theses questions please.

Determination of Iron By Titration with Permanganate oals: techniques for doing accurate titrations. Quantitatively determine the amount of iron in an unknown. Pre-lab Questions on page 69. Turn in when you come to class! Background: In this experiment, you will be using the titration techniques you learned in a previous lab (Acid-Base Titration) to accurately determine the concentration of a potassium permanganate solution. Then you will use the KMnO4 solution to accurately determine the amount of Fe in an unknown. The net-ionic equation for this redox titration reaction is shown below: 5 Fe2+(aq) + MnO4Taq) + 8 H+(aq) ? 5 Fe"(aq) + Mn2+(aq) + 4 H2O(I) purple yellow In the experiment, a soluble iron(II) salt is placed in an Erlenmeyer flask along with water and H2S04(aq). The sample is titrated by adding KMnO4(aq) from the buret. In the net-ionic equation above the Fe comes from a soluble iron(II) salt (described below) and the MnO4 comes from KMnO Previously, you carried out an acid-base titration where a color change from an indicator was used to determine the endpoint. In this experiment, an indicator is not needed because of the dark color of the titrant (KMnO4). The permanganate ion is deep purple in color, and the manganese (II) ion is nearly colorless. The endpoint of the titration is signaled by a change from the colorless Fe2 solution to a faint orange/pink color (due to a slight excess of permanganate). The yellow Fe will affect the shade of pink at the endpoint (you should see a pale orange color at the end point) The goal of the first part of the experiment is to standardize (precisely determine the molarity) the KMnO4 solution. This is done by carrying out the titration with a known quantity of the iron(II) salt, Fe(NH4)2(S04)2 6H2O. This iron(II) salt is a soluble, strong electrolyte. One mole of the iron(II) salt will dissolve to produce one mole of Fe2t H20 Fe(NHah(S04)2 6H20(s)Fe (aq) +2NH(aq)+ 2s0 [molar mass- 392.16 g/moll (aq) Once the MnO concentration (which is the same as the KMnO, concentration) has been determined precisely, this standardized solution can be used to determine the amount of iron in an unknown iron (II) salt in the second part of the experiment. The same chemical reaction [equation(1)] is used in the second part of the experiment, but a different iron compound is used. It contains iron as Fe, but the anion is not known. After doing a titration, the concentration and volume of permanganate solution will be used to find moles of Mn0 that were required to oxidize all of the Fe. The moles of iron are found using the 5:1 mole ratio in equation(1) above. Then moles of iron are converted to grams of iron. The percent of iron is the ratio of the mass of iron to total mass of the compound, with the fraction converted to a percent. is experiment. Potassium permanganate is o strong oxidizing agent. It will NOTE: Wear gloves for thi stain your hands and clothes. Be careful with the KMnOs solution!

Explanation / Answer

Solved the first three question, please post one more question to get the remaining three answers

Q1)

The reaction is basically an oxidation-reduction titration, if some of the iron is present in +3 oxidation state, then that won't be getting oxidized in presence of KMnO4, only the iron present as Fe(+2) will be getting oxidized

This will lead to low value of iron presence in the sample, since the Fe(+3) won't react with KMnO4

The calculated percent of Iron will be too low

Q2)

We need to exaclty measure the volume of de-ionized water since the molarity of the Fe(+2) in the solution will depend on the amount of solvent

Molarity = Number of moles of solute/Volume of solution (in L)

If we use low or high value, then it will affect the molarity of the solution and will lead to wrong results in the titration experiment

Q3)

There is no need of indicator for this experiment. Since the KMNO4 is purple color liquid, after completion of the reaction, it will change to MnO2 and the purple color will disappear which will lead to the know the exact end point of titration

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