Question

The number of moles of \[MnO_{4}^{-}\] and \[C{{r}_{2}}O_{7}^{2-}\] separately required to oxidize 1 mole of \[Fe{{C}_{2}}{{O}_{4}}\] each in acidic medium respectively are:
A.\[0.6,\text{ }0.5\]
B.\[0.6,\text{ }0.4\]
C.\[~0.5,\text{ }0.6\]
D.\[0.4,\text{ }0.5\]

Answer 1

Hint: Write the reactions of both the given compounds with \[Fe{{C}_{2}}{{O}_{4}}\] and find out the no. of moles used in the reaction, correspondingly find the no. of moles of both for 1 mole of \[Fe{{C}_{2}}{{O}_{4}}\].

Complete Step By Step Solution:
The reaction of \[MnO_{4}^{-}\] with \[Fe{{C}_{2}}{{O}_{4}}\] is given as-
\[3MnO_{4}^{-}+5Fe{{C}_{2}}{{O}_{4}}+24{{H}^{+}}\to 3M{{n}^{+2}}+5F{{e}^{+3}}+10C{{O}_{2}}+12{{H}_{2}}O\]
Here 5 moles of \[Fe{{C}_{2}}{{O}_{4}}\] are reacting with 3 moles of \[MnO_{4}^{-}\]. So, for 1 mole of \[Fe{{C}_{2}}{{O}_{4}}\], the no. of moles of \[MnO_{4}^{-}\] are- \[\dfrac{3}{5}\] \[=\text{ }0.6\]
Similarly, the reaction of \[C{{r}_{2}}O_{7}^{2-}\]with \[Fe{{C}_{2}}{{O}_{4}}\] is given as-
\[C{{r}_{2}}O_{7}^{-}+2Fe{{C}_{2}}{{O}_{4}}+14{{H}^{+}}\to 2C{{r}^{+3}}+2F{{e}^{+3}}+4C{{O}_{2}}+7{{H}_{2}}O\]
Here 2 moles of \[Fe{{C}_{2}}{{O}_{4}}\] are reacting with 1 mole of \[C{{r}_{2}}O_{7}^{2-}\].So, for 1 mole of \[Fe{{C}_{2}}{{O}_{4}}\], the no. of moles of \[C{{r}_{2}}O_{7}^{2-}\] are- \[\dfrac{1}{2}\]\[=\text{ }0.5\] .

Therefore, the correct option is A.

Additional Information:
\[MnO_{4}^{-}\] : Permanganate is a manganese Oxo anion and a monovalent inorganic anion. It is a conjugate base of per manganic acid. Generally purplish colored. soluble in water, Noncombustible, but accelerate the burning of combustible material. If the combustible material is finely divided, the mixture may be explosive. May spontaneously ignite in contact with liquid combustible materials. Contact with sulfuric acid may cause fire or explosion.
\[C{{r}_{2}}O_{7}^{2-}\]: Dichromate\[\left( 2- \right)\] is a divalent inorganic anion obtained by removal of both protons from dichromic acid. It is a chromium Oxo anion and a divalent inorganic anion. It is a conjugate base of a hydrogen dichromate

\[Fe{{C}_{2}}{{O}_{4}}\]: Ferrous oxalate, or iron (II) oxalate, is an inorganic compound with the formula \[FeCO\]
• \[xHO\] Where x is typically 2. These are orange compounds, poorly soluble in water. Its molar mass is around\[143.91g/mol\] .

Note: Study the chemical reactions of the given compounds, their dissociation into ions and the no. of moles used per reaction. Learn how to find the no. of moles. Concepts regarding \[C{{r}_{2}}O_{7}^{2-}\] and \[MnO_{4}^{-}\]their properties, molar masses, type of reaction they undergo, nature of the ions.