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.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.