O B. The total mass of the reactants equals the total mass of the
products.
A. Would be the correct answer :-)
Due to energy being a reactant instead of a product, the process is endothermic. The system must absorb a quantity of energy before it can react, so it must be an endothermic system.
P x V = n x R x T
P x 73 = 2.97 x 0.082 x 298
P x 73 = 72.57492
P = 72.57492 / 73
P = 1.0 atm
hope this helps!