Q4 / 90 · JEE Main 2023 (12 Apr Shift 1) · Chemistry

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 from Mg→MgO at ~1120oC

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
    A is false but R is true
  • Correct answer
    C
    Both A and R are true and R is the correct explanation of A
  • D
    A is true but R is false

Solution

Figure

For line II ∆S is more negative than line I. In the Ellingham diagram, a sharp change in slope of the line is observed for Mg-MgO at ~1120oC because that is the boiling point of magnesium.

From diagram, ∆SI=(Ssolid)-(Ssolid+Sgas)∆SII=(Sliquid)-(Ssolid+Sgas)

There is a large increase in entropy associated with the change of state of magnesium.

So, both Assertion (A) and Reason (R) are true and (R) is the correct explanation of (A).

Hence, the correct answer is option: 'C'.

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