Which of the following statements is true?
a. the entropy of a system always decreases for a spontaneous process.
b. a spontaneous reaction is always a fast reaction.
c. perpetual motion machines are a possibility in the near future.
d. there is a "heat tax" for every energy transaction.
e. none of the above is true.

The correct answer is D.

Explanation:

In every process that includes an energy transaction or transition, inevitably a little amount of energy in heat form will be lost. Regardless if the process is spontaneous or not, the loss of energy (heat tax) will be present always. Also, it is impossible to make a perpetual machine, not always a spontaneous reaction will be fast, and only in certain cases the entropy could decrease during a spontaneous process.

Therefore the correct answer is D.

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.