Question

1 mole of \[C{r_2}{O_7}^{2 - }\] oxidizes _____ moles of \[Fe{C_2}{O_4}\] in acidic medium.

Answer 1

Hint: In \[C{r_2}{O_7}^{2 - }\], chromium will get reduced from +6 to +3 oxidation state. \[Fe{C_2}{O_4}\] will get oxidized to form ferrate ions and carbon dioxide gas. We can balance the oxidation and reduction half reactions to see how much moles of particular species will be required to get the reaction done.

Complete Step-by-Step Solution:
This is a redox type of reaction.
- Here we can say that chromium in \[C{r_2}{O_7}^{2 - }\] will be reduced from +6 to +3 oxidation state in presence of acidic media. We can write the oxidation reaction as below.
\[C{r_2}{O_7}^{2 - } + 14{H^ + } + 6{e^ - } \to 2C{r^{3 + }} + 7{H_2}O\]
- Now Iron oxalate (\[Fe{C_2}{O_4}\]) will be oxidized to carbon dioxide gas and iron will get oxidized from +2 to +3 state. The reaction is shown below. Here in the process of oxidation, iron will give one electron and oxalate anion will give two electrons in the process of getting oxidized.
\[Fe{C_2}{O_4} \to F{e^{3 + }} + 2C{O_2} + 3{e^ - }\]
Thus, from the reactions we can see that one mole of dichromate ions require 6 electrons to get reduced and one mole of Iron oxalate require 3 moles of electrons.
So, we can say that one mole of \[C{r_2}{O_7}^{2 - }\] will oxidize 2 moles of \[Fe{C_2}{O_4}\] in acidic medium.

Additional Information:
- If any reducing agent and oxidizing agents are given to predict the amount of theirs required to complete the reaction, then we can follow the steps given below.

- First write the full oxidation and reduction half reactions properly and then compare the numbers of electrons required to complete the reaction. Then write the total reaction accordingly in a way that the number of electrons required is made the same by multiplying the contents.

Note:Here note that In Iron oxalate, not just Iron gets oxidized from +2 to +3 oxidation number but oxalate ion also gets oxidized to carbon dioxide gas which gives a total of 3 electrons. Always remember that dichromate ions reduce to give chromium in +3 oxidation state only, no other oxidation state of chromium is possible, we need to remember that.