A 20.0L container holds 0.650 mol of He gas at 37.0C at a pressure of 628.3torr. The new pressure inside the container will be
torr if the volume is reduced to 12.OL, the temperature increased to 1770, and 1.25 mol of
additional He gas was added.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.