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11. ⇒  (MHT CET 2021 20th September Evening Shift )

The change in internal energy of a system depends upon

A. initial and final states of a system

B. path followed by system

C. total energy of final state only

D. number of steps involved in system

Correct Option is (A)

Internal energy is a state function.

12. ⇒  (MHT CET 2021 20th September Morning Shift )

Calculate change in enthalpy when 39 g acetylene is completely burnt with oxygen and enthalpy of combustion of acetylene is − 1300 kJ/mol.

(At. mass C = 12, H = 1)

A. − 975 kJ

B. − 650 kJ

C. − 1950 kJ

D. − 1600 kJ

Correct Option is (C)

C 2 H 2 (   g )  Acetylene  + 5 2 O 2 (   g ) ⟶ 2 CO 2 (   g ) + H 2 O ( ℓ ) ; Δ r H ∘ = − 1300   kJ   mol − 1

When 26   g of acetylene is completely burnt, the change in enthalpy = − 1300   kJ

∴ For 39   g of acetylene, the change in enthalpy

= − 1300 × 39 26 = − 1950   kJ