Final answer:
The number refers to the enthalpy change of the reaction, which can be determined by conducting the reaction under standard conditions in a bomb calorimeter. The enthalpy change for the reversed reaction is equal in magnitude but opposite in sign to the forward reaction. The number of gas molecules in the reaction can either increase or decrease depending on the stoichiometry of the reaction.
Step-by-step explanation:
The number being referred to in the question is the enthalpy change of the reaction (AH). This is the amount of energy released or absorbed during a chemical reaction. It can be determined by conducting the reaction under standard conditions in a bomb calorimeter.
For the reversed reaction, the enthalpy change is equal in magnitude but opposite in sign to the forward reaction. So if the forward reaction is exothermic (releases energy), the reverse reaction is endothermic (absorbs energy).
The number of gas molecules in the reaction can either increase or decrease depending on the stoichiometry of the reaction. If there are more gas molecules on the product side than on the reactant side, then the number of gas molecules will increase. If there are more gas molecules on the reactant side than on the product side, then the number of gas molecules will decrease.