In most cases of fischer esterification, the carboxylic acid is the more "valuable" piece and the alcohol is used in excess. let's say you are making the ethyl ester of an acid and use the ethanol in excess. what technique would be used to remove the excess ethanol?

There are a lot of separation processes. To name a few, these can be distillation, centrifugation, extraction, membrane or sorption process and many other. To know which is the best technique, you should know the property between two substances that have a stark difference. In this case, it is the polarity. Ethyl alcohol is more polar than ethyl ester and less dense. Thus, these two won't mix. So, take advantage of their density difference by decantation or centrifugation.

Answer;

Some mass is converted into energy in a nuclear reaction.

Explanation;Nuclear fission and nuclear fusion are the two types of nuclear reactions. Nuclear fusion involves the combining of two small nuclei to form a larger nuclei coupled with the release of energy. Nuclear fission on the other hand involves the splitting of a heavy larger nuclei to yield smaller nuclei and is also coupled with the release of energy.In both nuclear fission and nuclear fusion reactions, energy is converted to mass.In nuclear fission, the resultant products have a slightly smaller nuclear mass as compared to heavy nucleus. This difference in mass is because some mass is converted to energy during the fission.Similarly in nuclear fusion some of the mass of the initial nuclei is converted into energy in the form of heat or light.