What chemical does the brain release to smother the synapses and stop transmission of the sensation of pain?

Does anyone know a lot about how to: - calculate mass of magnesium metal - calculate the actual yield of magnesium oxide - calculate the theoretical yield of mgo - calculate the percent yield of mgo - determine the percent yield of mgo - determine the average percent yield of mgo i had to do an online lab and its asking these questions but i have no idea where to start or how to be able to find these things. i can post the chart of the data from the lab or if you can tell me exactly how i can find each.

Which feature do highland climates have that lower elevation areas do not?

How do you identify the anode on a power source such as a battery? how do you identify the cathode? how are terms anion and cation?