Identify the compounds A, B, C and D in the following sequences of reactions:
CH3CH CH2 Ch > A Mg, ether B-CO2, ether >c_H2O/H4>D

the answer is 303.15 or 303

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.