The reaction ba(no3)2(aq) + na2so4(aq) → 2nano3(aq) + baso4(s) goes to completion because a

This reaction is completed by a double displacement

A double displacement occurs when two different salts are mixed in an aqueous state, since when they dissolve a salt their ions are dissociated and when mixed with another salt in an aqueous state they combine and form two new compounds

Double displacement reactions

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.