For the formation of Cr_2 O_3 and Al_2 O_3 , values of Δ_f G^ are 540 ~kJ ~mol^ -1 and -827 ~kJ ~mol^ -1 respectively. What will be the possibility for reaction of Cr_2 O_3 by Al ?

Correct answer: A. Reduction of Cr_2 O_3 by Al will take place aligned & 2 Cr+(3)/(2) O_2 Cr_2 O_3 ; Δ_f G^ =-540 ~kJ ~mol^ -1 & 2 Al+(3)/(2) O_2 Al_2 O_3 ; Δ_f G^ =-827 ~kJ ~mol^ -1 aligned Substrating equation (i) from (ii) gathered 2 Al+Cr_2 O_3 Al_2 O_3+2 Cr Δ_r G=[-827-(-540)] kJ mol^ -1 =-287 ~kJ ~mol^ -1 gathered because for the reduction by A l , value of Δ G^ is negative, therefore reaction is feasible.

JIPMER 2016

Exam: JIPMER
Year: 2016
Subject: Chemistry
Chapter: General Principles and Processes of Isolation of Metals

JIPMER 2016 · Chemistry · General Principles and Processes of Isolation of Metals

For the formation of Cr_2 O_3 and Al_2 O_3 , values of Δ_f G^ are...

For the formation of

\mathrm{Cr}_2 \mathrm{O}_3

and

\mathrm{Al}_2 \mathrm{O}_3

, values of

\Delta_f G^{\circ}

are

540 \mathrm{~kJ} \mathrm{~mol}^{-1}

and

-827 \mathrm{~kJ} \mathrm{~mol}^{-1}

respectively. What will be the possibility for reaction of

\mathrm{Cr}_2 \mathrm{O}_3

by Al ?

Options

AReduction of $\mathrm{Cr}_2 \mathrm{O}_3$ by Al will take place
BOxidation of $\mathrm{Cr}_2 \mathrm{O}_3$ by Al will take place
CNeither oxidation nor reduction will take place
DReaction is not feasible

Correct answer

A. Reduction of $\mathrm{Cr}_2 \mathrm{O}_3$ by Al will take place

Step-by-step solution

\begin{aligned} & 2 \mathrm{Cr}+\frac{3}{2} \mathrm{O}_2 \longrightarrow \mathrm{Cr}_2 \mathrm{O}_3 ; \Delta_f \mathrm{G}^{\circ}=-540 \mathrm{~kJ} \mathrm{~mol}^{-1} \ldots \\ & 2 \mathrm{Al}+\frac{3}{2} \mathrm{O}_2 \longrightarrow \mathrm{Al}_2 \mathrm{O}_3 ; \Delta_f \mathrm{G}^{\circ}=-827 \mathrm{~kJ} \mathrm{~mol}^{-1} \ldots\end{aligned}

Substrating equation (i) from (ii)

\begin{gathered}2 \mathrm{Al}+\mathrm{Cr}_2 \mathrm{O}_3 \longrightarrow \mathrm{Al}_2 \mathrm{O}_3+2 \mathrm{Cr} \\ \Delta_r G=[-827-(-540)] \mathrm{kJ} \mathrm{mol}^{-1}=-287 \mathrm{~kJ} \mathrm{~mol}^{-1}\end{gathered}

because for the reduction by

A l

, value of

\Delta G^{\circ}

is negative, therefore reaction is feasible.

Practice General Principles and Processes of Isolation of Metals on Quantrex Academy →

More from General Principles and Processes of Isolation of Metals

The reaction that does NOT takes place in blast furnace between 900K and 1500K… NEET 2023 Read the following statements and choose the set of correct statements: (A) Chrome steel… NEET 2023 Match List-I with List-II. List-I (Ores) List-II (Composition) (a) Haematite (i) Fe _ 3 O… NEET 2022 Which one of the following methods can be used to obtain highly pure metal which is… NEET 2021 The maximum temperature that can be achieved in blast furnace is: NEET 2021 Identify the correct statement from the following: NEET 2020 Match the elements in Column I with methods of purification in Column II. Column-I… NEET 2020 Assertion : ZrI_4 is useful in purification of zirconium (Zr). Reason : ZrI_4 sublimise… AIIMS 2019 Full General Principles and Processes of Isolation of Metals list All JIPMER PYQs