Long-run marginal cost is the slope of the long-run total cost curve. With TC (Q) =2 Q, the slope of the long-run total cost curve is 2, and thus MC (Q) = 2. Long-run mar-ginal cost also does not depend on Q. Its graph is the same horizontal line.This exercise illustrates a general point.ong-run marginal cost is the slope of the long-run total cost curve. With TC (Q) =2 Q, the slope of the long-run total cost curve is 2, and thus MC (Q) = 2. Long-run mar-ginal cost also does not depend on Q. Its graph is the same horizontal line.This exercise illustrates a general point.
Combustion Definition. Combustion is a chemical reaction that occurs between a fuel and an oxidizing agent that produces energy, usually in the form of heat and light. Combustion is considered an exergonic or exothermic chemical reaction. It is also known as burning.
Key Concepts. 1  Heat of Combustion of a substance is the heat liberated when 1 mole of the substance undergoes complete combustion with oxygen at constant pressure. 2  Combustion is always exothermic, the enthalpy change for the reaction is negative, Î´H is negative. Combustion is always exothermic, the enthalpy change for the reaction is negative, Î´H is negative. 2  By definition, the heat of combustion is minus the enthalpy change for the combustion reaction, ie, -Î´ reaction H. 3  By definition, the heat of combustion is a positive value.