During a reaction, the enthalpy of formation of an intermediate is 34 kJ/mol. During the reaction, 4 moles of the intermediate are produced. What is the
enthalpy value for this step of the reaction?
A. 34 kJ
B. 136 kJ
C. -136 kJ
D. -34 k

b. examine and describe cells

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.