A gaseous mixture of O2 and N2 contains 38.6 % nitrogen by mass. What is the partial pressure of oxygen in the mixture if the total pressure is 0.803 atm

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.