NEETChemistryThermodynamics (C)
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): For the reaction CO (g) + 1 2 O ₂ (g) CO ₂ (g) at 300 K, given U^ = -280.0 kJ mol ⁻¹ and S^ = -86.0 J K ⁻¹ mol ⁻¹ , the reaction is spontaneous. Reason (R): For this reaction, H^ is more negative than U^ , and the magnitude of H^ is greater than the magnitude of T S^ , making G^ negative. (Given :
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
First, evaluate the Assertion (A) by calculating the thermodynamic parameters. The change in gaseous moles for the reaction is: n_g = n_p - n_r = 1 - (1 + 0.5 ) = -0.5 Calculate H^ at 300 K: H^ = U^ + n_g R T H^ = -280.0 + (-0.5) (8.3 10⁻³) 300 H^ = -280.0 - 1.245 = -281.245 kJ mol ⁻¹ Calculate the entropy term T S^ : T S^ = 300 (-86.0 10⁻³) = -25.8 kJ mol ⁻¹ Calculate G^ : G^ = H^ - T S^ G^ = -281.245 - (-25.8) = -255.445 kJ mol ⁻¹ Since G^ is negative, the reaction is spontaneous. Thus, Assertion (A) is correct.