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Question: When chromium metal is tied, to form \({K_2}C{r_2}{O_7}\) ​, the oxidation state of chromium changes...

When chromium metal is tied, to form K2Cr2O7{K_2}C{r_2}{O_7} ​, the oxidation state of chromium changes. Select the right option.
A. 00 to 44
B. 33 to 66
C. 22 to 66
D. 00 to 66
E. 22 to 44

Explanation

Solution

Potassium dichromate is highly used as an oxidizing agent in organic chemistry. It is used to oxidize alcohol. It converts the primary alcohols into aldehydes and, under more forcing conditions, into carboxylic acids. Potassium dichromate is generally prepared by the reaction of potassium chloride on sodium dichromate. Alternatively, it can even be obtained from potassium chromate by roasting chromite ore with potassium hydroxide. It is generally soluble in water and in the dissolution process it ionizes:

K2Cr2O7  2  K+  +  Cr2O72{K_2}C{r_2}{O_7}\; \to {{ }}2\;{K^ + }\; + \;C{r_2}{O_7}^{2 - }

Complete step by step answer:
The chemical compound, potassium dichromate is an ionic compound consisting of two potassium cations and one dichromate anion. The coordination geometries around the chromium atoms are known as tetrahedral.

Potassium is known to exhibit an oxidation state of +1 + 1, oxygen exhibits an oxidation state of 2 - 2
So, the total charge of potassium ions is +1(2)=+2\, + 1\left( 2 \right) = + 2\, while oxygen ions is 2(7)=14\, - 2\left( 7 \right) = - 14\,
Let xx be the oxidation number of two chromium atoms.
Hence we can write the equation as below:

2+x14=0\,2 + x - 14 = 0\,

12+x=0\, - 12 + x = 0\,

x=12 \Rightarrow x = 12

So, two chromium atoms will have an oxidation number of +12 + 12
So one chromium atom would have an oxidation number of

+122=+6 \Rightarrow \dfrac{ +12}{2} = + 6

So oxidation number of CrCr inK2Cr2O7\,{K_2}C{r_2}{O_7}\, is equal to +6 + 6
Therefore, in the molecule potassium exhibits an oxidation state of +1 + 1, and oxygen exhibits an oxidation state of 2 - 2. Chromium exhibits an oxidation state of +6 + 6

So, the correct answer is Option D .

Note: Oxidation number, also known as the oxidation state, is the total number of electrons that an atom will either gain or lose to form a chemical bond with another atom in a chemical reaction. Every atom that participates in an oxidation-reduction reaction is given an oxidation number that reflects its capability to acquire, donate, or share electrons. An atom having higher electronegativity (even if it forms a covalent bond) is usually given a negative oxidation state.