Which statement is true? a. the enthalpy for the formation for two moles of a substance is half of the enthalpy for the formation of one mole of the substance. b. the enthalpy of a reaction is the heat of reaction at constant volume. c. the enthalpy of a reaction is the negative of the enthalpy of the reverse reaction. d. the enthalpy of a reaction and the enthalpy of the reverse reaction are equal.

Analyze the reaction to determine whether the reaction is exothermic or endothermic. explain your reasoning.

Using this reversible reaction, answer the questions below: n2o4 2no2 (colorless) (reddish-brown) -as the temperature increased, what happened to the n2o4 concentration? -was the formation of reactants or products favored by the addition of heat? -which reaction is exothermic? right to left or left to right? -if the change of enthalpy of this reaction when proceeding left to right is 14 kcal, which chemical equation is correct? n2o4 2no2 + 14 kcal n2o4 2no2, hr = +14 kcal n2o4 + 14 kcal 2no2 n2o4 2no2, hr = -14 kcal

What lessons does the history and study of the periodic table offer to other fields of science, and the pursuit science more generally