Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: In the Ellingham diagram, a sharp change in slope of the line is observed for Mg MgO a

Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: In the Ellingham diagram, a sharp change in slope of the line is observed for Mg MgO at 1120 °C Reason R: There is a large change of entropy associated with the change of state In the light of the above statements, choose the correct answer from the options given below

(A) Both A and R are true but R is NOT the correct explanation of A
(B) Both A and R are true and R is the correct explanation of A
(C) A is true but R is false
(D) A is false but R is true

Prashant Kotian · Accepted Answer

Correct answer: B. The diagram predicts that MgO and ZnO ought to decompose if heated strongly enough, but it does not hold out much hope for obtaining say pure Mg by straight forward heating of the oxide to a high temperature where the boiling point of the metal is exceeded. However the slope increases since the reaction is now involving a larger entropy change as the randomness increases in reactants. For example, 2 Mg(g) + O2(g)  2 MgO(s) Here, three moles of gas phases are converted into solid phase in the reaction. This takes place above 1120ºC, which is the boiling point of Mg.

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