Which formulas represent one ionic compound and one molecular compound?

ionic compounds lose or gain electrons to become stable.
ionic compounds are bonds between metals and nonmetals.

molecular or covalent compounds share one or more electrons to become stable.
molecular or covalent compounds are bonds between nonmetals.

the answer to this question is 3.

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.