When water evaporates at constant pressure, the sign of the change in enthalpy: a. is negative b. is positive c. depends on the temperature d. depends on the volume of water e. does not exist because the enthalpy change is zero D 100 When water evaporates, the forces holding one water molecule to another water molecule (hydrogen bonds) must be broken. To break these connections, heat energy needs to be added. Therefore this is an endothermic process with a positive delta H. 1 D 200 D 300 2H2S + O2 ? 2S + 2H2O If 102 g of H2S are combined with 64 g of O2, what is the maximum mass of elemental sulfur that could be produced by the reaction? D 400 Fe2O3 + 3CO ? 2Fe + 3CO2