question_answer 1)

  In the following questions a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below: (a) Both A and R are true and R is the correct explanation of A. (b) Both 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. Assertion (A): Combustion of all organic compounds is an exothermic reaction. Reason (R): The enthalpies of all elements in their standard state are zero.

Answer:

  (b): Combustion of organic compounds is always exothermic. Heat or enthalpy of formation of natural elements in their standard state is considered to be zero.