NEETChemistryThermodynamics (C)
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The entropy change ( S ) for the combustion of solid magnesium to form solid magnesium oxide is negative. Reason (R): The reaction involves a decrease in the total number of moles of gaseous species. In the light of the above statements, choose the most appropriate answer from the options given bel
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- BBoth (A) and (R) are true but (R) is not the correct explanation of (A)
- C(A) is true but (R) is false
- D(A) is false but (R) is true
Correct answer
A. Both (A) and (R) are true and (R) is the correct explanation of (A)
Step-by-step solution
The balanced chemical equation for the combustion of solid magnesium is: 2 Mg ( s ) + O ₂( g ) 2 MgO ( s ) In this reaction, the reactants contain 1 mole of gaseous species ( O ₂ ), while the products contain 0 moles of gaseous species. The change in the number of gaseous moles is n_ g = 0 - 1 = -1 . Because there is a decrease in the number of gaseous moles, the randomness or disorder of the system decreases. Consequently, the entropy change ( S ) for the reaction is negative. Therefore, Assertion (A) is true. Rea