Magnesium reacts with hydrochloric acid, HCI, to form magnesium chloride and hydrogen gas. The reaction is: Mg + 2HCI -> MgCl2 + H2 What is the mass of HCl that would be required to completely react with 5.2 grams of Mg? 6.9 O 16 0 6.934 O 15.60 ​

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.

5.6⋅10−^19  j

do you need the explaination?

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".