One of the classic methods for the determination of the manganese content in steel involves conv

One of the classic methods for the determination of the...

Key Concepts

Permanganate Ion Chemistry

The permanganate ion (MnO4–) is a powerful oxidizing agent with a deep purple color, making it ideal for spectrophotometric detection. Its formation from Mn(II) via oxidation is central to methods that rely on color change for quantitative determination.

Analytical Chemistry Techniques

Analytical methods in chemistry often exploit specific chemical reactions to convert an analyte into a form that is easier to detect and quantify. In the determination of manganese in steel, the conversion to a colored permanganate ion allows for sensitive and selective measurement, typically using absorption spectroscopy.

Transition Metal Oxidation States

Transition metals such as manganese can exist in multiple oxidation states, each with distinct chemical properties and colors. The ability to convert a less visible form (Mn(II)) to a vividly colored form (Mn(VII), in the form of permanganate) underlies many analytical methods in metal analysis.

Redox Reactions

Redox (oxidation–reduction) reactions involve the transfer of electrons between species, which results in changes in their oxidation states. The determination of manganese content by converting Mn(II) to Mn(VII) demonstrates a typical redox process where electron transfer plays a crucial role in altering the chemical form for analysis.

Balancing Redox Equations

Balancing redox equations requires ensuring that both mass and charge are conserved while accounting for electron transfer. In acidic solutions, this often involves adding water, hydrogen ions, and electrons to appropriately balance the reduction and oxidation half-reactions.

Transcript

00:02 So here the question is one of the classic methods of the determination of the magnesium content in the steel involves converting all the manis to the deep colored per magnetion and then measuring the absorption of light.

00:21 The steel is first dissolved in nitric acid producing the magnesium 2 plus ions and nitrogen dioxide gas.

00:31 This solution is then reacting with the acidic solution containing per iodide ion.

00:40 The products are the permacetate and iodide ions.

00:45 Write balanced chemical equation for both of these steps.

00:52 Now here the first step is very important to know that read the question carefully and try to understand what is asked.

01:02 Both these reactions are actually redox reactions and we have to balance this reaction.

01:08 So first reaction is when steel is dissolved in nitric acid, the mn present in the steel is the first reaction.

01:31 The mn present in the steel reacts with the hno3 nitric acid and forms mn2 plus ion and no2 ion.

01:41 So first we have to take this reaction and here the reaction given is mn which is present in the steel is reacting with the nitric acid and forming mn2 plus ion and anode gas.

02:10 So first this reaction we have to balance and for balancing any redox reaction first step is see the oxygen.

02:23 Oxidation state of all the elements which are present and try to differentiate oxidation reaction and reduction reaction so, i mean here as a metal, so oxidation state should be 0 here hydrogen should be always at plus 1 oxygen is at minus 2 1 oxygen minus 2 and nitrogen should be 3 minus 1 that means plus 5 oxidation state of nitrogen should be plus 5 and mn here whatever charge that should be oxidation state nitrogen here oxygen will remain minus 2 so nitrogen should be at plus 4 oxidation state these are the oxidation states just to identify oxidation half reaction and reduction half reaction and it is totally different from the charges present over the molecule.

03:45 So after knowing this we can see where the oxidation state is changing.

03:51 From mn to mn2 plus this should be increase in oxidation number.

03:57 So this is oxidation.

04:00 So oxidation half reaction is mn is converted to mn2 plus.

04:18 This is oxidation half reaction.

04:21 After that identification we have to balance this reaction and reduction half reaction should be hno3 is converted to nitrogen reduction is taking place from plus 5 to plus 4.

04:43 So this is the reduction half reaction where hno3 is converted to no2.

04:52 This is a reduction half reaction.

04:54 So one by one we are balancing this.

04:57 First step is see the oxidation state and accordingly add the electron.

05:06 So from 0 to plus 2 to get this 2 electron must be removed from it.

05:12 Then only we can get add electron accordingly.

05:15 So this is the first step for balancing the half -reaching.

05:21 After that, in the next step, balanced the, actually it was balance all other elements except hydrogen and oxygen.

05:35 So mn is already balanced after that we are coming to this step where you have to see the oxidation state and accordingly you have to add the electron.

05:45 Then balance the charge.

05:48 Here also it is zero this side and right -hand side also charge is zero.

05:54 And by this, this whole reaction is balanced by means of charge and by means of number of atoms in both the side.

06:09 It is balanced.

06:10 Now come to the reduction half reaction.

06:13 In the reduction half reaction again, we have to balance.

06:16 All other elements except hydrogen and oxygen.

06:21 So nitrogen here one, here also it is one, so it is already balanced.

06:25 After that see the oxidation state and add electrons accordingly.

06:31 So from plus 5 it is converted to plus 4.

06:36 That means one electron is added.

06:42 So we are adding this side...